Related Links:
Kodak Ektar Lenses
Kodak Ektar Lens Page (Kodak made own glass..)
Large Format Lenses
See misc. lenses notes by Michael K. Davis linked at Links Page

This page archives some postings on optical glasses, who makes optical glasses, tolerances of optical glass makers (e.g., Leitz vs. other mfgers), specialty glasses, and interesting lenses (e.g., Kodak Ektar lenses). Enjoy!

P.S. Use your browser search function (CTRL-F on PCs or Cmd-F on Macs) for searches...

Related Postings

From: [email protected] (HRfoto)
Newsgroups: rec.photo.equipment.medium-format
Subject: Glass Manufacturers
Date: 7 Jul 1998

Does anyone have substantiated infromation about which lens manufacturers make their own glass? I know that Leitz, Zeiss, Nikon, Minolta do, and I aminterested in other companies doing the same.

Thanks for your info.

Heinz Richter

Newsgroups: rec.photo.equipment.medium-format
To: HRfoto [email protected]
Subject: Re: Glass Manufacturers
Date: Mon, 06 Jul 1998

Heinz,

I work with lens manufacturers now and again and am involved in lens design. I don't think any of these folks make their own glass. Maybe you mean the grind or mold their own lenses. Most designers specify the type of glass from a specific foundry and then either grind/mold them from the material or contract it out to various manufacturers.The quality of a lens has little to do with who makes their own or doesn't make their own.....it has more to do with the type of glass for a given application and how the elements are designed and coated. Also, when it comes to molded lenses, it is a function of how careful the mold was made and tested/refined (in the case of aspherical elements). The other big factor is assembly. How well are the individual elements placed and centered. This can make a lens with great glass and a great name into junk.

Of course the Zeiss lenses tend to be great....and cost a lot. Even if individual lens makers formulated and made their own raw glass, they might not have much of an advantage over the rest of the manufacturers since there are literally hundreds of high quality glasses formulations out there. The problem with camera lenses is the volumes keep going down. High quality lenses are always lower volume and the lower the volume the higher the price goes. The still camera market appears to be getting smaller each year.

Dave

From: [email protected] (HRfoto)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Glass Manufacturers
Date: 7 Jul 1998

>I work with lens manufacturers now and again and am involved in lens design.
>I
>don't think any of these folks make their own glass.

Yes they do. I have visited the Leitz manufacturing plant and have seen some of the processes involved. And I do know for a fact that the other manufacturers mentioned by me do make their own glass also. That isn't to say that other lens manufacturers can't get the same or similar glass by giving specs to a company like Schott. But Leitz and Zeiss for instance do have glasses available which are developments of their own, and which are trade secrets. One such glass is the socalled APO glass from Leitz. It was originally developed by the Leitz glass research lab for a lens system for the US Navy. It is a glass with an extremely high refractive index (over 1.9) and with a rather low Abbe number (dispersion). While most glasses are identified by an alpha numerical code, like LaK9, these glasses have only a code number which doesn't reveal any of its properties to outsiders.

I am seeking this information purely for its historical facts. I am not so naive to think that a company needs to make its own glass in order to produce good lenses. However, I have also done a lot of research of how lenses are designed and made. Obviopusly, the quality of the design, the quality of the glass, the quality of the manufacturing process, they all influence the overall quality of the resulting lenses. I have obtained the performance figures of one of the lenses, which Leitz made for the US Navy. It is now available as the 180mm Apo-Telyt R. Compared to performance data from other lenses, there simply isn't anything even close to this lens available from anyone else. Subsequently, in the final analysis, making ones own glass can, and does, make a difference.

Heinz Richter

Newsgroups: rec.photo.equipment.medium-format
To: HRfoto [email protected]
Subject: Re: Glass Manufacturers
Date: Tue, 07 Jul 1998

Heinz,

That is interesting to hear about Leitz. In my industry we do not work with German manufacturers because the competition for low price rules out manufacturers in Europe. The demand for high quality remains though. So, I am more familiar with North American (yes, there are some good optics houses in the U.S. and Canada) and Asian companies who some of the time make lenses for their own brand named products and/or make OEM lens assemblies for other companies. I think many folks would be surprised to know who it is that makes lenses for some brand name cameras. Bet everybody thought Norita was gone (if you have ever seen an old Norita camera!)....but they are still out there making OEM lenses.

However, when it came time to invest in a lens for my 4X5, I didn't hesitate to buy Rodenstock. I have had a chance recently to work with Minolta, and they do mold and grind some of their own lenses, but I am pretty sure they don't make their own raw glass. Minolta does some really fine work and I am not sure why Minolta cameras have always been percieved as non-pro equipment (at least in North America) with Canon and Nikon seeming to dominate the pro market. Many might also be surpirised at how many companies Minolta makes lenses for.

Interesting topic

Dave

Editor's Note: Kowa, the makers of a range of 35mm and the Kowa 6/66 medium format cameras, are also reportedly still in business making lenses. Kowa made some of the most extreme lenses in medium format photography. See Kowa 6x6 19mm f4.5 fisheye...

From: [email protected] (David L. Glos)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Glass Manufacturers
Date: Tue, 07 Jul 1998

Interesting that you mention Norita. I have a couple of their old 120 SLR's, and the optics are quite good for their age. I have the 40/4, a couple of 80/2's and a 160/4. The 80 is simply superb, and the 40 is great, even to the edges, by f/8. Absolutely first rate for the $425 I paid for that lens. The 160 is no slouch, but not in the same league as the 40 and 80. Flare is an issue, particularly with the 40, although, I can only assume they are single coated, which may be part of the issue. Careful use of lens hoods make it pretty much a non-issue.

Would be interesting to hear what they are into now.

David Glos

Univ. of Cincinnati
513.558.6930
[email protected]

Newsgroups: rec.photo.equipment.medium-format
To: "David L. Glos" [email protected]
Subject: Re: Glass Manufacturers
Date: Tue, 07 Jul 1998

David,

Your right, Norita made some nice optics and still do. It doesn't surprise me that you have to be careful with flare though, since optics from that period did not have sophisticated coatings. Norita still makes lenses. They built a projection lens that I was involved in designing about 4 years ago. They build lenses for a number of different companies for projectors and maybe even cameras. OEM's are typically pretty tight lipped about who they build for though, so it is hard to know exactly where their optics show up, but I bet some camera manufacturers have been using them along with the projector market. They also make lenses and optical components for the "three gun" large screen TV market.

Regards,

Dave

From: [email protected] (Helge Nareid)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Glass Manufacturers
Date: Tue, 07 Jul 1998

Dave [email protected] wrote:

>I work with lens manufacturers now and again and am involved in lens design. I
>don't think any of these folks make their own glass.

I know that Nikon make at least some of their own glasses - notably the "ED" high index, low dispersion glasses used in their expensive telephoto lenses. I believe that Canon make their own fluorite glass used for the same type of products. Minolta has advertised as one of their strong points that they make their own optical glass, and I've read Fuji literature which make a great to-do about the platinum-lined crucibles they use for melting their optical glasses. Nevertheless, the biggest manufacturer of optical glasses in Japan is Hoya.

>Maybe you mean the grind or
>mold their own lenses. Most designers specify the type of glass from a specific
>foundry and then either grind/mold them from the material or contract it out to 
>various manufacturers.

The most well-known maker of optical glass is probably Schott, and their catalog is mandatory on any lens designer's desk. Their BK7 crown glass is virtually the industry standard for optical glass. Other major makers include Corning and Hoya (as mentioned above).

>The quality of a lens has little to do with who makes their
>own or doesn't make their own.....it has more to do with the type of glass for a
>given application and how the elements are designed and coated. Also, when it
>comes to molded lenses, it is a function of how careful the mold was made and
>tested/refined (in the case of aspherical elements). The other big factor is
>assembly. How well are the individual elements placed and centered. This can make 
>a lens with great glass and a great name into junk.

To exagerrate just a _wee_ bit - these days any 14-year old with a PC and suitable optical design software can design a great lens. In real life, of course, experience and knowledge of lens theory is mandatory to get optimum results. However, designing a wonderful lens system is not particularly costly, and I expect that even the cheapest lenses are excellent performers in computer simulations.

What _is_ expensive is build quality, which affects things like element placement, centering and tolerancing. These are very important details when it comes to real lens performance. As Dave has pointed out, this alone can make the difference between a great lens and a mediocre one. Also, a well-built lens will take much more punishment before image quality is affected.

Another much-neglected issue in lens design has nothing to do with the glass at all - baffling and suppression of stray light. This is costly and not particularly glamourous, but it can be just as important as the difference between multi-coating and single coating of the elements. It doesn't make as good advertising copy, unfortunately. Lens hoods should be mandatory for serious photographers for the same reason.

>Of course the Zeiss lenses tend to be great....and cost a lot. Even if individual 
>lens makers formulated and made their own raw glass, they might not have much of
>an advantage over the rest of the manufacturers since there are literally hundreds
>of  high quality  glasses formulations out there.

I'm pretty sure that Zeiss don't make their own glass - both Carl Zeiss and Schott Glaswerke were incorporated in their present form by Ernst Abbe, and I'm pretty sure that all the glass used by Zeiss have been made by Schott ever since. Both were located in Jena (in Eastern Germany) until the end of the war, and the American occupation forces in Germany reestablished both companies in the US zone by transferring key personell. The East German branches continued under the names of Carl Zeiss Jena and Jenaer Glas, respectively, and were merged with their western equivalents after the German reunification.

So I agree with Dave, with the possible exception of highly specialized and expensive glasses used for glamourous fast telephoto lenses, the actual manufacturer of the glasses used is not particularly important. Of course, the glasses must be accurately specified, and made to a high degree of uniformity, which is why there are only a handful of major manufacturers of optical glasses - the economics of scale are very important in a highly competetive market.

--
- Helge Nareid
Nordmann i utlendighet, Aberdeen, Scotland

rec.photo.equipment.large-format
From: [email protected] (Thor Lancelot Simon)
Re: Ektar Lenses
Date: Mon Jul 13 1998

Michael Liczbanski [email protected] wrote:

>Which Ektars and what vintage?  They do differ considerably in quality and
>specs.

Actually, I don't think that's generally acknowledged to be the case.

All Ektars were Kodak's premium-priced lenses for professional use, and though new glass and better coatings gradually became available over time, the basic designs changed very little. Most Ektars were Tessar formula lenses, with a scattering of 4-element air spaced and dialyte lenses. The "Commericial Ektar" lenses were corrected for minimal lateral color (like a modern lens) and, as the last Ektars made, had the best coatings.

Kodak's quality control was reputedly better than that of any other contemporary lens manufacturer and their designers while not enormously innovative were certainly extremely competent.

This is some email from Tim Takahashi (who collects Kodak lenses) which I saved a while ago (note it doesn't include most of the longer focal lengths):

| This is what I know....
|
| >from  the "classic" era of Kodak lenses
|
| 50mm f/2.0 Ektar     - 828 Kodak Bantam Special - 6-element Gauss
| 78mm f/3.5 Ektar     - 620 Kodak Chevron - 4-element Tessar
| 80mm f/6.3 WF Ektar  - 4-element W.A. Gauss
| 100mm f/6.3 WF Ektar - 4-element W.A. Gauss
| 100mm f/3.5 Ektar    - 620 Kodak Medalist - 5-element Heliar
| 101mm f/4.5 Ektar    - Tessar
| 105mm f/3.7 Ektar    - Heliar
| 127mm f/4.7 Ektar    - Tessar
| 135mm f/6.3 WF Ektar - 4-element W.A. Gauss
| 152mm f/4.5 Ektar    - Tessar
| 178mm f/2.5 Aero Ektar - 7-element
| 190mm f/4.5 Ektar    - Tessar
| 203mm f/7.7 Ektar    - 4-element Dialyte
| ..
|
| I'm packing to move (new job), so I dont have my reference
| books handy. That's what I'm sure of off the top of my head.
|
|
| >Many of the earliest Ektars (non-commercial) were labled "Anastigmat"
|
| Not quite. K.A's were uncoated lenses... and when the Ektar series
| debuted in 1939, all had some form of anti-reflection treatment
| (though the early ones have soft coatings on the inner surfaces
| only).
|
| The high-end line continued to be marketed as "Anastigmat" and
| "Eastman Anastigmat" until after WW-II. Afterwords these were
| re-released (re-computed???!?!) as Commercial Ektars.
|
| -tim
|
| >I guess it's all dependant upon who Kodak bought from in the early
| >days.
|
|
| ps. Kodak made all lenses "in house" - Rochester has a large
| number of now defunct glassworks.

--
Thor Lancelot Simon
[email protected]
"And where do all these highways go, now that we are free?"

rec.photo.equipment.large-format
From: "Michael Liczbanski" [email protected]
Re: Ektar Lenses
Date: Mon Jul 13 1998

Thor Lancelot Simon wrote

>Michael Liczbanski [email protected] wrote:
>>Which Ektars and what vintage?  They do differ considerably in quality and
>>specs.
>
>Actually, I don't think that's generally acknowledged to be the case.

Ah, but it is the case:

The quality varies depending on the vintage & purpose of Ektars... I realize that the original post was most likely about the LF Ektars, but many MF Ektars are on the market as well (sometimes sans their original cameras so one cannot tell without testing whether or not they cover 4x5...) Here is a brief description of just a few Ektars:

Kodak Ektar 2/45 (for Bantam Special) 6 elements in 4 groups, covers 28x40mm negatives

Kodak Ektar 3.5/100 (for Kodak Medalist) 5 elements in 3 groups, covers 2 1/4 x 3 1/4 (and 6.5x9 cm)

Kodak Ektar 3.7/105 4 elements in 3 groups, covers 2 1/4 x 3 1/4 *** A very good lens, also used on the Precision enlarger. Sharp and contrasty.

Kodak Ektar 4.5/101 and 4.7/127 4 elements in 3 groups, covers 2 1/4 x 3 1/4 and 3 1/4 x 4 1/4 respectively *** Also a great lens, esp. for 6x9

Eastman Ektar 6.3/8 1/2in; 6.3/10in; 6.3/12in; 6.3/14in 4 elements in 3 groups, these lenses cover 5x7 to 8x10in. The 14 inch covers also 11x14 at f/16 and below, but without much room for movements. *** Great, fully corrected lenses (coated!) Expensive, big and still very useful even today. All have a great circle of coverage and a very "sweet", "full bodied" shadow detail. The minimum f stop is f/45, whereas I'd prefer f/64 or even smaller for 8x10.

Kodak Ektar 1.9/50; 3.5/50; 3.3/35; 3.5/90; 3.8/105; 4.5/135 (for Kodak Ektra) All cover (some barely) 24x36mm. Come in a variety of designs (even a nice triplet at 3.5/90) and their quality varies from lousy (1.9/50 esp. wide open) to superb 3.5/50, 3.3/35.

>
>Many of the earliest Ektars (non-commercial) were labled "Anastigmat"
>

Well, the Anastigmat was a separate line of lenses - essentially Tessars with the exception of the 6.3/105, 6.3/130 and 7.7/8in. Some notable Anastigmats were: 7.7/8in Covers 5x7 "process" lens, well-corrected for close-up work. Quite nice

5 1/2in, 6 3/8in, 7 1/2in, 8 1/2in, 10in and 12in - all f/4.5 Cover from 3 1/4 x 4 /1/4 to 8x10 (with movements) depending on the focal length. Fine lenses (great for architecture, as they don't display much linear distortions of any kind.)

There were also Anastigmats for small format cameras (35mm, Bantams and Vigilants)

Well after WWII, Kodak started tinkering with their lenses a lot, and the distinctions between many lens lines blur in the 50s. (The summary above describes the mid-to-late 40s status quo.)

Just my USD .02.

Michael

rec.photo.equipment.large-format
From: "Michael Liczbanski" [email protected]
Re: Ektar Lenses
Date: Mon Jul 13 1998

OK, here are the numbers (actually in the Kodak catalogue, the numbers precede the lens name:) All data come from Kodak Reference Handbook, 1946 (practically unchaged from 1940-1946.)

No. 31 Kodak Anastigmat f/4.5 5 1/2in (140mm) No. 32 Kodak Anastigmat f/4.5 6 3/8in (161mm) No. 33 Kodak Anastigmat f/4.5 7 1/2in (190mm) No. 34 Kodak Anastigmat f/4.5 8 1/2in (216mm) No. 35 Kodak Anastigmat f/4.5 10in (254mm) No. 36 Kodak Anastigmat f/4.5 12in (304mm)

All appear to be Tessars (4 elements in 3 groups, 4 internal air surfaces)

No. 70 Kodak Anastigmat f/7.7 8in (203mm)

(Symmetrical, air-spaced, 4 elements in 4 groups, 6 internal air surfaces.) BTW, that's the one I like on a 4x5 VC the best (it will cover 5x7, but with 4x5 you'll sooner run out of swings and titlts, than go beyond its circle of coverage.)

Michael

rec.photo.equipment.35mm
Date: Mon Jul 06 1998
From: [email protected] (Rudy Garcia)
Re: Glass Manufacturers

[email protected] (HRfoto) wrote:

> Does anyone have any substantiated information about which lens manufacturers
> actually produce their own glass?  I know that Leitz, Zeiss, Nikon Minolta do,
> but am interested to know who else.
> Thank you
>
> Heinz Richter

Tokina does for sure. It is a part of the Hoya corporation. Hoya, among other things, makes glass masks for the semiconductor industry.

rec.photo.equipment.35mm
From: [email protected]
Re: Glass Manufacturers
Date: Wed Jul 08 1998

"David W. Swager" [email protected] wrote:

> Now I was under the impression that Zeiss did not make glass, but bought it
> all from Schott since they are under the same ownership.  This is the big
> pitch for B+W that they get their glass from the same place Ziess does!

Optical glass is made by several big suppliers and some smaller ones. Schott is the biggest in Germany, Hoya the bigget in Japan. Tamron is also a major Japanese glass maker. Good optical glass is also now made in China by state- owned factories.

Where a company gets its glass is simple economics. For ordinary crown and flint glass types, companies will buy from the cheapest source. I have been in a factory in Germany and seen Schneider lenses being made from blanks supplied by Tamron because that was the cheapest source at the time. I don't think any lens maker ALWAYS buys from one source.

Now when you get to proprietary formula specialty glass like the UD types the situation changes, and these are most often made in house or from one controlled supplier.

Bob Shell

rec.photo.equipment.35mm
Date: Fri Jul 10 1998
From: Steve [email protected]
Re: Glass Manufacturers

Rudy Garcia wrote:

>
> [email protected] wrote:
>
> > Does that mean that I can be buying a $1200 german lens, and really be
> > getting a cheaper glass?
> >
>
> Do you also want to specify the particular beach in Germany the sand
> (Silicon Dioxide) came from?
>
> For most optical glasses, the quality of the results are mostly determined
> by the care and the equipment that went into creating the lens.
>
> From there, it is the optical prescription, multicoating and the mechanism
> that keeps the elements in alignment, plus the care that went into
> assembly/alignment.
>
> Good quality special glass can be obtained by buying industrial grade
> glass blanks, remelting it and adding the special "secret" formula
> ingredients, such as fluorites, etc.
>

Specialty glass, such as that produced by or for Nikon and Zeiss for their lenses, are not made from industrial glass blanks, melted or otherwise.

The sand is special - sure, most all "glass" sand is high in silica, but the glass used in these special lenses is made from sand with a very high purity level.

Several different metals are added to glass to give it certain characteristics. You'll notice that window pane glass, especially if viewed through the edge of the glass, has a green color. This comes from iron in the glass, and the iron comes from the leaching that occurs with the highly corrosive molten glass eats into the iron vats in which it is melted.

You've probably noticed that your lenses have no green tint - there is two ways to prevent green tinting - 1. Melt the glass in a Platinum crucible, or 2. Add lots of lead - that's why "leaded" crystal glass is so clear. But leaded glass has poor light transmitting characteristics, and is not suitable for lenses.

Some lead has to be added even to that glass melted in the Platinum pots, or the lump of glass will be obscure, with a white haze.

After the other secret ingredients are added to the molten glass (for lenses), it is left to cool at a slow rate. It is then broken into large peices, each of which is tested for light transmitting characteristics. A whole bunch is rejected (and sold to cheaper manufacturers!). Only about 5% of the batch is suitable for lens making (for Zeiss , Nikon, and other scientific uses such as optics for the US Space Program). That's one of the reasons the expensive lenses are so expensive.

Window pane glass and "plate" glass use the whole pot of molten glass, and there is none thrown away (as a matter of fact, the crucibles are sometimes dozens of yards yards long, and cullet is shoved in one end, and molten glass is "pulled" into sheets on the other end. It is a continuous process, and the batch runs 24 hours per day).

Hope this clears it up a bit more for you, and that I haven't been too much of a "pane",

Steve Vise
Vise Glass Inc.

rec.photo.equipment.35mm
Date: Tue Jul 07 1998
From: [email protected] (Rudy Garcia)
Re: Glass Manufacturers

[email protected] (HRfoto) wrote:

> >> Does anyone have any substantiated information about which lens
> >manufacturers
> >> actually produce their own glass?
> >Tokina does for sure.  It is a part of the Hoya corporation.  Hoya, among
> >other things, makes glass masks for the semiconductor industry.
>
> I don't doubt that your information is correct.  However, I would like to know
> how this information was obtained.  Making glass masks for the semi conductor
> industry doesn't require a glass manufacturing plant.  As a matter of fact,
> even glass manufacturers like Leitz and Zeiss buy  a substantial amount of
> inexpensive glass from Schott.
>
> Regards,
>
> Heinz

Because I'm in the semiconductor (one word) equipment industry. Photography is only my hobby. I happened to have had a need for some special glass blanks of very high optical flatness some years ago and did some research to find a suitable vendor.

You can verify it for yourself at: http://www.hoya.co.jp/

--
Use address below for Email replies. Address on Header is bogus to defeat AutoS PAM.

[email protected]
Rudy Garcia

Date: Wed, 15 Jul 1998
From: michael collier [email protected]
To: Robert Monaghan [email protected]
Subject: Re: why do lens costs differ so much? Re: Glass Manufacturers

> yes, I agree with many of your points re:exotic lens production - these
> were all basically hand-made lenses - hence costs - 1200mm canon is
> another good example ;-) ditto 55mm schneider tilt/shift

I wonder if it works out better to do several at a time, rather than one at a time, on these? if you can load up the grinding machine with 20 elements of a given kind, or the coating cooker machine, or turn a set of 20 barrel parts of a given kind, or whatever, and then shelve the components until there is a demand? i could get quick turnaround on those nikon 6/2.8 and 13/5.6 lenses i have wanted for so long (at $15K a pop :-).

> re: Mamiya rb/rz67 - doesn't Zorkendorfer make a tilt/shift mount for the
> RZ like they do for the mamiya 645 etc?

apparently so, and mamiya does one as well (maybe that is the zorkendorfer). mamiya is getting set to release 75 and a 180 "short barrel" lenses that will apparently fit the T/S adapter and the #1 extension tube, and focus at infinity. for that T/S to work for me, i need more like 20mm of rise (like the current 75 shift lens), or maybe 25mm to 30mm :-). the flange distance on the T/S is on the order of 25mm, and on the #1 is on the order of 45mm, so maybe there is a new T/S adapter with a 45mm flange distance in the works....

> Unfortunately, RZ/RB have
> 105/102mm lens registration distances, so don't know of any 35mm
> retrofocus lenses that have coverage like that ;-(

you would need a way to spread the image circle, like the hassy 1.4 shift mutar.

> hard to beat angulon
> 47mm in 4x5 or 2x3 view camera mount for cost anyway - hence impact on
> market to make 'em for 6x7 or 6x6 - you can't win ;-( - or maybe that's
> just a good excuse to buy 'em all ;-) ;-)

yeah, that 47 is great, and rodenstock has a 35 now (120 degree field). actually, i have considered trying that 35 against 8x10: superwide rectilinear circular image. it would give my clients a "look" they haven't seen before....

--
Michael H. Collier
[email protected]

From: [email protected] (HRfoto)
Newsgroups: rec.photo.equipment.35mm
Subject: Manufacturing tolerances
Date: 17 Jul 1998

Some time ago I obtained a broshure from Leitz, which stated various tolerances in the production of their cameras and lenses. For comparison I contacted a number of other camera and lens manufacturers and unfortunately did not get the replies I was hoping. Nikon claimed proprietery information. Canon did not answer, neither did Minolta. The worst answer came from Pentax, stating that this was a very complicated matter and that I wouldn't be able to understand it anyway. Who do they think they are to tell me what I know, or not know for that matter. The most honest answer came from Bronica. They stated that they were primarily a sales organization here in the US and they didn't have a clue what I was talking about. They said the request had been forwarded to Japan, but I never heared back.

Has anyone any information in this regard?

Here is what I have been able to gather: The industry standard for camera equipment is tolerances to 1/1000". Canon, with the introduction of the F1n proudly claimed that they had increased tolerances to 1/1250". Leitz and Zeiss (when they still made cameras themselves) apply tolerances of 1/2500". The international standard for glass requires tolerances of +/- 0.001% for the refractive index and +/- 0.8% for the Abbe number (dispersion). The Leitz data are +/- 0.0002% for refractive index and +/- 0.2% for the Abbe number. Allowable tolerances during lensproduction for Leitz are 1/4 Lambda or 1/4 of the average wavelength of light, which amounts to 0.0002 mm. Minoltas tolerances in this regard are 0.0003 mm. Needless to say, the Leitz testing equipment, much of which is manufactured in house, is made to specifications exceeding the figures above.

The focusing mounts of Leitz lenses are machined to the same tolerances as their cameras, 1/2500" or 1/100 mm. Considering the wobble in the focusing mounts of most autofocus lenses, one must ask how accurate those can be.

Anyway, any additional input here would be very much welcome.

Heinz Richter
HRphotography

Subject: Re: Manufacturing tolerances
From: "Jim Williams" [email protected]
Date: Fri, 17 Jul 1998

It sounds as if you have already made up your mind what you WANT the answer to be: "Finer tolerances are better, and Leica has the finest tolerances, so they are the best."

In fact, ALL those assumptions are dubious: "finer" tolerances are not necessarily better; and Leica (which no longer has any relationship to the Leitz company, by the way) isn't necessarily "finer" than others by any meaningful measure. In fact, I'm very dubious that today's photo industry adheres to any blanket numbers such as "industry standard... tolerances to 1/1000" -- a single all-encompassing tolerance figure just isn't the way modern manufacturing is done.

In fact, the best and most honest answer to your question may have been the one you got from Pentax: the issue of manufacturing tolerances IS very complex, and can't really be explained fully without getting into pretty heavy statistical concepts. However, here's a *broad* outline of how industry addresses the issues of tolerance (I just had to wade through all this stuff in a training course for my employer) and why all those specific +/- numbers you cited aren't all that relevant to the way they do things:

One of the breakthroughs of late-'40s technology -- and possibly the key factor in propelling the Japanese into their present pre-eminence in the field of precision manufacturing -- was the concept of "statistical process control." This concept was pioneered by Americans including the now-famous W. Edwards Deming -- who couldn't get American or European manufacturers interested in it, so taught it to the Japanese (which explains why one of their most prestigious industrial honors is called the Deming Award.) Now, of course, the concept is used by almost every manufacturer (although I'm not sure about Leica!)

Before statistical process control, most precision manufacturing was done by the methods we still like to think of as "old-fashioned high quality craftsmanship" as exmplified by Leica, Zeiss-Ikon, Rolls-Royce, etc. This involved specifying an "ideal" dimension for each part of the product; viewing tolerances as "errors" and holding them as small as possible, even if it meant rejecting a lot of parts; doing lots of hand-fitting in an effort to bring the dimensions of each assembly into an acceptable range; and relying on rigorous final inspections to weed out the defective units that inevitably got manufactured. This method resulted in nice final products, but at the cost of slow production, high waste rates, and hefty cost. (It's the main reason that the high-quality cameras of the '30s and '40s were mainly the playthings of extremely wealthy gents, while mainstream photographers could only afford equipment that was often pretty rotten.)

Statistical process control considers the entire manufacturing process differently. Rather than looking at each part individually, it starts by looking at the entire product and determining what level of performance it's expected to meet (for example, how accurately the flange-to-film distance in an SLR must be maintained to assure accurate focusing.) It uses statistical calculations to determine what ranges of variation can be accepted in various subassemblies, then designs the components and manufacturing processes to fall within those ranges. And instead of relying on a single, intensive final inspection to weed out defective items, it samples and tests subassemblies throughout the process, again using statistical mathematical principles to assure that "If X% of this part and Y% of this part test out within acceptable limits, we can be Z% certain that the ENTIRE batch of finished products meets our goal."

It's this concept of tolerance *distribution* -- of using statistics to control the *total* variability of the manufacturing process so that the final product meets the desired standards -- that makes it unrealistic to ask a manufacturer "What tolerances do you use in manufacturing your product?" Some of the tolerances permitted may be very small; others may be very large. What counts in a statistically-controlled manufacturing process is the *performance* specification of the *finished product,* not the *mechanical* specifications of the parts that go into it. The entire manufacturing process is designed and statistically controlled to assure that the varying attributes of the component parts will combine into a finished product that reliably meets the performance criteria.

Here's an old-vs-new example of how the idea of tolerance distribution works, again relating to that critical dimension of lens-flange-to-film-plane distance. In an old Leica, an assembler would obtain the correct distance by starting with a camera body casting and a lens flange, both carefully made at great expense to be as precise as possible. However, this was never quite precise enough. So, the assembler would select a casting and a flange that he thought would match from the parts bins... measure their depths... and select thin brass shims to fit between them. He'd then assemble the unit, test it with a gauge, add or remove shims, test it again, etc., until he had an assembly that met tolerances.

In a current SLR, the lens flanges and body castings come together on an assembly line and are assembled automatically. It isn't necessary to measure the exact depth of each flange or body casting, or to put shims between them -- their production has been statistically controlled so that they fall within an acceptable range, and that's all they need to do. Their *exact* individual dimensions don't matter -- because the next step is that the whole assembly is chucked into a machine that holds it by the lens flange and then planes off the film guide rails to provide the required depth and parallelism. Tolerances of the individual parts may have been looser, but the performance of the final assembly is just as good (probably better) because the entire process has been designed to put the accuracy *where it counts*

I know you are not going to like this answer...

From: Keith Whaley [email protected]
Subject: Re: Manufacturing tolerances
Date: Fri, 17 Jul 1998

To condense a 4 page comment and response into little more than a few words, this whole thread is ridiculous. Here's some person who wants to know the manufacturing tolerances to which any given camera manufacturer adheres. Why? What would it do to enhance his enjoyment of the camera or help him get better pictures?

I'd be willing to bet that in cameras, as within almost every other precision mechanical device anyone could mention, the tolerance applied is only as tight as what is necessary for each of the mating parts to do their job in concert.

Six adjacent parts could have +.0010, -.0005" to a shaft hole, while right beside it, some other part is perfectly happy operating within a total tolerance of plus or minus .010." Which is more meaningful? Neither. Each does it's part as is necessary.

Asking *any* manufacturer what tolerances they work to is evidence that the asker hasn't a clue. There are several hundred tolerances given to the parts in most modern cameras. Perhaps thousands. Shall they pick the best and tightest tolerance case and confuse him, which is tantamount to lying to him?

Then, he talks about optical tolerances in the same breath as mechanical tolerances. What's the point of that? Comparing optical tolerances used with the mechanical tolerances used in a camera is comparing an elephant's dimensions and gnat's eyebrows. Unless it's simply to show that he is aware of the tolerancing of various elements within a camera. Most interesting and commendable, but so what?

Anything a camera company comes up with, with respect to how tightly they hold tolerances, is 98% advertising hype, and is mostly meaningless.

Let's get on to some other subject that can aid another photographer get his job done. . .

If the original poster wants to pursue his quest for total knowledge of the camera manufacturers business, that's just fine with me, but let's not fill up this News Group with minutiae.

keith whaley

From: [email protected] (Neuman-Ruether)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Manufacturing tolerances
Date: Sat, 18 Jul 1998

Heck, I can't resist... (though Jim Williams' answer was a darn good one...! ;-). I check out a lot of lenses (see my "SLE{MN]", under "I babble" on my web page), and have seen a lot of sample variation in a VERY few Nikkors, some variation in some lenses, and very little in most, especially the non-zooms. But I have seen manufacturing defects in a rather surprising percentage of the small number of Leitz rf lenses I've seen (and even a bit of visible misalignment in a 3-kilobuck 35mm f1.4 double-aspheric...). BTW, while I'm not fond of the look and feel of the icky plastic AF lenses (with NONE of the panache of Leitz rf lenses, or Nikkor MF lenses...! ;-), even with the front optics flopping all about, they still can check out well-aligned optically... A Leica rangefinder camera is fun to hold and handle, but when it comes to picture taking, it would sit on my shelf, and the F3 and 8008 would go out to work.

David Ruether
[email protected]

From: [email protected] (Helge Nareid)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Glass Manufacturers
Date: Tue, 07 Jul 1998

 Dave [email protected] wrote:
>> The most well-known maker of optical glass is probably Schott, and
>> their catalog is mandatory on any lens designer's desk. Their BK7
>> crown glass is virtually the industry standard for optical glass.
>> Other major makers include Corning and Hoya (as mentioned above).
>
>Absolutely, BK series is the most common, although it is also common for  lens designers
>to mix elements that are each made of a different glass to correct for chromatic and
>other aberrations.

Indeed, but I work a lot in holography, interferometry and other laser-related applications, where chromatic corrections are irrelevant, so a lot of the components I handle (singlet lenses, prisms, beam-splitters, windows, etc) use the cheapest high-quality glass which is readily available - i.e. Schott BK7 or equivalent. I think it's safe to say that most components involving only a single type of glass (in the visible region) will use BK7 or a similar glass type, unless there is a compelling need for another glass. I'll have to admit to having used SF11 and other glasses at need, however. I've never yet had to use a glass which is not in the standard Schott catalogue (or Hoya or Corning), but the day may still come...

>This is where the experience of a designer comes in and shines over
>a teenager with a PC.

Sorry about that one ;-) I am of course aware that there is a lot of skilled work involved in the design of a good lens. The tools available these days are pretty good, however, and relieves the designer from a lot of the tedious work which earlier workers in the field had to put up with. The very thought of leafing through printed 8 digit trigonometric tables for each ray and each surface to be traced makes me shudder. I only tried to point out that the cost of the design is a very small proportion of the total cost of bringing a lens to market these days, so even very cheap lenses may have a brilliant basic design. The actual physical implementation of the design is an entirely different matter, of course.

--
- Helge Nareid
Nordmann i utlendighet, Aberdeen, Scotland

Date: 8 Jul 1998
From: HRfoto [email protected]
To: Robert Monaghan [email protected]
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: why do lens costs differ so much? Re: Glass Manufacturers

>b) the glass is made and sold by 3rd party in many cases - so its same
>$$, right? [possible differences for make your own types - Canon
>fluorites etc?]
>c) grinding appears a similar cost item, similar tolerances, gear costs etc?

I tried to obtain production tolerances from Nikon, but was not able to do so. However, I do have a lot of information in this regard for Leitz products. Tolerances are not as much the same as you assume.For instance, the international standard for tolerances of the refractive index is +/- 0.001%, Leitz on the other hand specifies tolerances no larger than +/- 0.0002%. Even if they purchase raw glass from outside suppliers, this will substantially increase cost. The same is true for the Abbe Number(dispersion), where the international standard is for tolerances of no more than +/-0.8% while Leitz specifies +/-0.2%. The same is true for the manufactur of individual lens elements. Leitz allows tolerances of no more than 1/4 Lambda, or 1/4 of the average wave length of light. There are cost differences in regard to raw glass also. The so called Apo glass, which is produced only by Leitz is appr. 100 times more expensive to make and use than the average optical glass. Finally, their mechanical tolerances can not be any greater than 1/100 mm or 1/2540". Such stringent tolerances DO add to the price of equipment, but it will also pay of in noticeably higher performance figures. In comparison, the allowable tolerances for lens manufacture of Minolta are 33% coarser, and when Canon introduced the F1n, they proudly stated that they increased their tolerances from the industry standard of 1/1000" to 1/1200".

>f) quality control checks - I suspect this is where the big differences
>in cost lie? But isn't QC or QA rather good already in process of mfging?

With mass produstion QC is only possible once and so often. Leitz on the other hand uses what they refer to as a bench made process, where every lens elemnt is checked several times. Individual lens elemnts then are sorted by their deviation (within tolerances) from the ideal. This then is taken into cosideration during lens assembly to cancel out random deviations. The result is virtually equal performance from lens to lens.

If it is worth to pay the extra cost for all of this depends on the needs of the individual.

Best regards,

Heinz Richter
HRphotography

From: [email protected]
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Glass Manufacturers
Date: Thu, 09 Jul 1998

[email protected] (Helge Nareid) wrote:

>  Dave [email protected] wrote:
>
....

>
> I'm pretty sure that Zeiss don't make their own glass - both Carl
> Zeiss and Schott Glaswerke were incorporated in their present form by
> Ernst Abbe, and I'm pretty sure that all the glass used by Zeiss have
> been made by Schott ever since. Both were located in Jena (in Eastern
> Germany) until the end of the war, and the American occupation forces
> in Germany reestablished both companies in the US zone by transferring
> key personell. The East German branches continued under the names of
> Carl Zeiss Jena and Jenaer Glas, respectively, and were merged with
> their western equivalents after the German reunification.

Correct: Zeiss makes none of its own glass *except* for testing purposes. With their close ties to Schott, any commercial size batches are prepared by Schott. Source for this info: I know the chief economist at Schott and the patent attorney at Zeiss, whose wife is godmother to my youngest daughter!

> So I agree with Dave, with the possible exception of highly
> specialized and expensive glasses used for glamourous fast telephoto
> lenses, the actual manufacturer of the glasses used is not
> particularly important. Of course, the glasses must be accurately
> specified, and made to a high degree of uniformity, which is why there
> are only a handful of major manufacturers of optical glasses - the
> economics of scale are very important in a highly competetive market.

It is the specification which is critical, as well as the quality of manufacturing *and* quality control. That is why Zeiss lenses are so expensive: each one goes through quality control, not only every thousandth or so that is typical of mass consumer lenses. Helps to drive the prices way up.

jfo

From: [email protected] (RABASTE)
Newsgroups: rec.photo.misc
Subject: Re: How do lenses affect colour?
Date: 20 Aug 1998

Hi Chris!

Lucky you! You start with a Nikon! Lenses are made of glass for the most part except lenses that are made of fluorite. It looks like glass but it's not. It's like comparing plexiglass windows with glass windows: they look the same but are not.

So, glass is a compound of silicate and other various chemicals. It's not a simple chemical you find on a chemistry chart. Until people figured out to add certain chemicals, glass was opaque (not good for lenses...).

The only true glass found in nature is opaque black and is called obsidian (if I remember correctly). Then by adding stuff to it, it became dark green but you could see through it ( anet improvement) and eventually later, adding more components, glass became clear. Adding lead made crystal...

Everybody tried various chemicals in different quantity and combinations and eventually became so specialized with their secrets that they became the lens manufacturer we know nowadays. Because all combinations are different from one manufacturer to another, they all have a different colour and different properties.

Diffraction, light index (how much light goes through), colour separation... Since there are so many problems besides design to deal with, the idea is to have the best glass possible, but nothing is perfect. Glass with good light index may separate colour on planes that do not match emulsion layers...

They need to be multi-coated to fend off stray light and during that process, manufacturers try to coat their lenses by bombarding electrons from other chemicals so they stick as a layer that correct for a colour flaw.

So, some people are known to create better glass than others and some people are know to coat lenses better than others. Bottom line is everybody tries their best. Prices on lenses don't just come from the glass but also the design.

In general if you spend so much time designing a lens, you put the best glass you can and still stay competitive in the market. I believe the only way to judge lenses is by shooting transparency film and do comparative tests. Oh, yes, different glass creates different contrast too!

Most manufacturers offer lenses that are similar in quality from one manufacturer to another but some stand out. Nikon, Canon, Leitz and Zeiss in 35mm. All lenses from the same manufacturer are usually matched to their own standard and you couldn't find much difference at first. You get a $100 lens from a manufacturer and get a $600 lens of same focal length from the same manufacturer, overall there is no colour cast but colours become more brilliant and vibrant (better contrast) in the expensive lens (of course...).

Keep in mind that in most applications until you specialize, any lens will do if you focus and get good light. Most great shots have great light (I'm not talking pinhole art photography here!). Keep in touch and good photography!

Bye!

Michel

[email protected] wrote

>Hi, I'm 15 and just got my first SLR. I'm new to photogrphy and I've been
>lurking in this newsgroup for a while and Ive already learned quite a bit but 
>I have a million questions and I'll probably have a million more.
>
>But my first one has to do with what someone said 
>about a lens having "nice  colour".
>
>How exactly does a lens affect the colour in an image? (besides  using filters)
>I just got a Nikon EM with a Nikkor 50mm lens for my birthday and I
>want to know what I should look for when I ask for a new lens maybe this
>Christmas. Is it just a cheap vs expensive lens thing or are there  different
>colour qualities to lenses?
>Thanks for your help.
>Chris   

From: [email protected] (CharlesW99)
Newsgroups: rec.photo.misc
Subject: Re: How do lenses affect colour?
Date: 31 Aug 1998

Advanced photographers sometimes will comment on whether a particular lens will produce a "neutral" versus "warm" or "cold" color balance. Basically the warmer tones are associated with red-orange part of the spectrum and cold tends towards blue.

I must emphasize that even with relatively inexpensive lenses, this is barely noticible.

I must also emphasize that if you shoot color negative film, any drift away from neutrality can be compensated to some degree by the lab. So don't look at color prints to judge. The lab can mess up and you can get a series of prints that look too green, too blue, or so on....

Also, the fact that a lens tends to produce slightly warm results is not so bad. That is why people use a skylight filter; to get the XS blue out of shadows and mountain shots. Some photographers go so far as to use a 2X skylight filter to warm things up. A lens which is too cold will tend to add a blue tint to the shadows or distant mountains.

The only way you can really check the color balance outside of an optical lab is to use slide film. If your slides seem to warm to you (assuming you didn't take the pictures just before sunset or near sunrise!) then don't use a skylight filter on the lens. If it looks too cold: use a Skylight or a skylight 2 filter.

Charlie

rec.photo.equipment.medium-format
From: [email protected] (lemonade)
Re: Hasselblad falling behind others
Date: Tue Oct 06 1998

[email protected] (Planar100) wrote:

> > Bob Salomon [email protected] wrote:
> > > 3: ? who makes the new short zoom? Not Zeiss and not Schneider and  obviously
> > > not Hasselblad.
> >
> > I'm suspecting it's fuji.
>
> It might be designed by Hasselblad but manufactured somewhere else. With
> today's software technology it's piece of cake compared to thirty years
> ago. Just leave the computer running over the weekend and then you'll
> have a new lens on monday morning with simulated MTF's and everything.

Hmmmmmmmm, sort of. It's true that one can easily evaluate any given lens design, but how does one come up with a new, original lens design in the first place? And, given any particular simulation result, how does one know which of the many parameters to tweak or change outright to get to the desired result? And how do you know what the desired result should be, what compromises are acceptable, what trade-offs best worth making? How do you know when and where to use an aspheric element or ED glass, or for that matter, any particular glass? These things cannot be invented or decided by computer, although I expect there are some algorithms for optimizations of given designs and likely modifications to standard designs, for standard improvements. But certainly for anything really new, or for the providing of goals and the resolution of what to trade off with what, computers are useless and only brains will suffice, i.e. brilliant, highly qualified optical engineers, who understand both lens design and the aesthetics of photography, and who one would expect to be tied very tightly (who knows, shackled in leg irons perhaps) to the historically great manufacturers.

--
Due to the intolerable volume of spam these days, I no longer supply a valid email address.

From: [email protected] (HRfoto)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Hasselblad & lens design
Date: 9 Oct 1998

>Re: Hasselblad & lens design
>
>> And, given any particular simulation result, how does one know
>> which of the many parameters to tweak or change outright to get to the
>> desired result? And how do you know what the desired result should be,  what
>> compromises are acceptable, what trade-offs best worth making? How do you
>> know when and where to use an aspheric element or ED glass, or for that
>> matter, any particular glass? These things cannot be invented or  decided by
>> computer

Sorry, but you are wrong with that assumption. Example: At the end of the 1960's the US Navy found the need for a high resolution 35mm system. They contracted E. Leitz Canada for the development. The required performance parameters were enterds into the Leitz EROS lens design computer system which developed a lens system requiring a glass type which was unknown at the time. However, knowing the properties of this glass as specified by the computer system allowed the Leitz glass research lab to develop this glass over a period of 3 years. The result was the so called Leitz Apo glass, which at the time resulted in the 180mm f/3.4 Apo Telyt and a number of other lenses utilizing the same glass. Other glass manufacturers were not able to produce their versions of glasses with anomalous dispersion until almost 10 years later. These lenses simply would have been impossible to produce without the help of the computer system.

Heinz Richter
HRphotography

Date: Mon, 19 Oct 1998
From: Bob Shell [email protected]
Subject: RE: [Rollei] Oh No! Yashika Again

>If yashica ever had a better optics, they would not have had contract  with CZ
>and introduced modern Contax. Rollei should be better now, but after the
>Contax 645
>hits the market. I don't know...

Actually, Yashica did not go to CZ, CZ came to Yashica. They were looking for someone with lots of experience in electronically controlled cameras. They had gone to Pentax first to build their new cameras, and Pentax was simply not up to the task or their standards, so they moved the project to Yashica. Pentax was left with the K-Mount as their legacy from this involvement with CZ.

This had absolutely nothing to do with Yashica's optics. CZ needed 35 mm cameras to put their lenses on after the decision to shut down camera production at Zeiss Ikon. Rollei was not in good shape at the time, so they did not want to pin their future lens sales on Rollei. That turned out to be a very wise decision.

Their alliance with Yashica carried with it one of those great bits of serendipity which occasionally shine in this industry. With Yashica they got Dr. Sugaya, a true genius, and the generation one and two Sugaya shutters used in the Contax RTS and RTS II. Dr. Sugaya also designed the vacuum back for the RTS III. I am told that even though he has been retired for some time he was also the driving force behind the new Contax 645.

At the time of the alliance with CZ, Yashica owned a semi-independent lens making factory under the name Tomioka. Tomioka, among other things, made some of the best lenses used by Polaroid on their cameras. Production of CZ lenses was set up as a separate line at the Tomioka works. Over the years, CZ took over more and more of Tomioka until today the whole thing has become a subsidiary of CZ.

Bob

From: [email protected] (David L. Glos)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Aero Ektar (Was: Newton Photo Products LF Camera????)
Date: Mon, 26 Oct 1998

>  I've never had an Aero Ektar to play with so can't testify from
>personal experience.  The explanation above doesn't quite make sense.
>Most lenses intended for use in ordinary photography are corrected at
>infinity.  Generally they will have good performence down to some
>limit like 10x focal length beyond which they will need to be stopped
>down some.  I don't know how the Aero Ektar could be different than
>this.
>  I've also read suggestions that the color correction of this lens is
>optimised toward the red since aerial cameras are nearly always used
>with yellow filters and often used with IR material. If this is true
>thei lens might exhibit some blue fringing. Someone who has a properly
>mounted Aero Ektar might be able to say whether it does this.       
>  This lens was intended for use in aerial reconnaissance, often with
>hand-held cameras and for night flash photography where lens speed was
>more important than exact geometry as in lenses meant for aerial
>mapping.  In other words, its design is more like an ordinary camera
>lens than the usual aerial survey lens.  It will be interesting to
>hear from those who have practical experience.
>  There was also BTW a 12" version of this lens.  It is a very
>impressive piece of glass.
>---
>Richard Knoppow
>Los Angeles, Ca.
>[email protected] 

FWIW, I was recently given a 24"/6.0 Aero Ektar that is very impressive in girth and weight. One of the elements in the rear group is yellow/brown in color and will peg the meter on a geiger counter, if placed within 6". Talked with several sources, including a retired military nuclear engineer, and all said not to worry too much as it was emiting alpa radiation from the trace of thorium (?) in the glass. I have yet to see how it will image as I don't have a camera large enough to put it on........and that includes an 8x10. On the barrel is an indication that it will cover 9x18. Current thoughts center around a panorama camera from hell, but backlog of projects exceeds time available to bring them to fruition. I have also thought about making a nice telescope with the beast.

BTW, I even talked with the Kodak person in charge of their historical archive. He knew of the 6" and 12", and had examples on their shelves, but had no record of the 24".

David Glos

Univ. of Cincinnati
513.558.6930

[email protected]

From: [email protected] (James Chow)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Why Japan cannot follow Germnay in lens technology ?
Date: 12 Nov 1998

[email protected] (EDGY01) wrote:

> Many decades ago I chose Japanese photographic equipment because,  frankly, I
> couldn't afford the cost of German equipment.  Fortunately, now, when price
> isn't a significant issue to me, I still prefer the Japanese equipment because
> of their leading designs and executions.  The Japanese don't appear to sit back
> and only release a new lens design every 20 years,--they are constantly making
> improvements in optics with the advent of lens designs, multicoatings, and the
> use of special glass.  They also develop some very special application  lenses
> that the Germans don't attempt to match, e.g., the PC Nikkors, and some of the
> more sophisticated projection fisheyes.    

True that companies like Leitz have been sitting on their laurels for decades making the same lenses, but CZ is (now that the Cold War has ended) working on new designs. My schneider-kreuznach medium format lenses (new designs from the mid 80's-mid 90's, also German) will match/surpass the zeiss/leitz lenses in optical quality (contrast, sharpness, bokeh), but this company concentrates solely on photographic (large format) lenses (BTW, they also make B+W filters). Zeiss (in the past) was trying to get out of the photo lens business since they were able to make more money off one submarine periscope then by selling 1,000 medium format lenses, so the money just wasn't there for R&D in photography. Now that the Cold War has ended, they're introducing new lenses for the Rollei, Hasselblad, and Contax lines, but it's nothing like in the 1950's-70's.

Also, now days, there's no advantage in labor costs by manufacturing Zeiss lenses in Japan. The only advantage is the superior mass-production technology that the Germans (nor anyone else) has yet to match. My medium format lenses are hand-assembled (limited production) in Germany, etc.(what else do you expect at $5K a pop) and still have much better feel/precision than the mass-produced Contax/Zeiss lenses. But the newest Japanese-made Contax 6x4.5 lenses will still cost $2.5K/pop, and that's with no leaf shutter.

In Japan, photographers favor German-made lenses. One reason is that the bokeh is much nicer (for portraits). Others say Japanese lenses are optimized for maximum sharpness in the center, while German optics are uniform from edge to edge. BTW, Zeiss and Schneider make tilt-shift lenses for both 35mm and 6x6 formats (Schneider makes a 28mm super angulon PC for the Contax/Nikon mounts...it's available in Japan for about the same price as what you'd pay for a Canon PC lens, but I guess in the US, there's no market for it).

--Jim

Date: Wed, 25 Nov 1998
From: Dirk-Roger Schmitt [email protected]
To: [email protected]
Subject: Re: [Rollei] SL 35 Rollei

>>Until a couple of weeks ago I didn't know Rollei ever made an SLR. But
>>then I saw one at an estate sale, and picked it up based on the name.
>>It's Singapore made, with Singapore 1.8 Planar HFT, and I also picked up
>>the Carl Zeiss Tele-Tessar f4/135mm HFT (German),
>
>There seem to have been Carl Zeiss HFT lenses.  That is, Zeiss would mark
>lenses made for Rollei with the "HFT" markings, as the two coating
>technologies are identical.
>
>The Singapore lenses almost certainly have German glass assembled in
>Singapore.  This is a subject of some contention at present, but we are
>tracking it down as I write this!
>
>Marc  

It would not have made sense for saving costs to do the polishing of the glass in Germany.

I know for sure that the Singapore factory had an own big optical workshop for polishing the lenses. And it also made no sense to by all glass material from Schott in Germany if Hoya delivered that for half the price from Japan. So, from case to case it could be that Rollei lenses made in Singapore contain also glass from Germany, but in general this would not make sense.

Greetings###

Dirk

Date: Wed, 25 Nov 1998
From: Bob Shell [email protected]
Reply to: [email protected]
Subject: Re: [Rollei] SL 35 Rollei

Marc,

Some of the Singapore lenses, particularly at the beginning, MAY have been made with elements ground, polished and coated in Germany.

The great bulk, however, were ground, polished and coated there in Singapore. Rollei had a complete optical plant there. They also made some lens elements for Schneider there, and these were shipped back to Germany and assembled into barrels, and, of course, marked "Made in Germany".

Rollei was building all sorts of stuff at their Singapore works, even electric typewriters!!!!

Bob

Date: Mon, 28 Dec 1998
From: Marc James Small [email protected]
Subject: Re: [Rollei] WHich filters on a Rolleicord II (I think a type 5 with the Triotar 3.5

Lucian Chis wrote:

>Jena is a city in the former East Germany where there has been a centuries
>old tradition of making glass. this is where Carl Zeiss started his
>company, and where the largest optical factories in the world existed
>until 1989. This factory peaked at something like 60000 employees. Din't
>care too much about camera optics but sure made a great job in defense
>contracts after the war. Now parts of that factory are owned by different
>Western part companies (Schneider, Docter come to mind).
>So before there was Oberkochen there is Jena!

> The assumption that resolution (in line pairs per millimeter) is higher
> for 35mm lenses than medium format lenses than large format lenses is
> partially based on fact, partially based on old wives' tales, and
> partially the result of stale data.
> [... (snip a good article) }

>[...] Real world lens designs have certain
> uncorrected aberrations that improve as you stop down.

> So, on paper, given the assumption that ideal lenses are sharpest wide
> open, the advantage would appear to go to the smaller format optics.

> This ignores one very important consideration.  This is only for the
> aerial resoltion of the image produced by the lens.  In the real world,
> we use film and cameras to record this image.

>Dirk-Roger Schmitt wrote:
>>Docter- Optic became bankrupt by overtaking the Zeiss plant.
>
>Well, no.  When the eponymous owner, Herr Dokter, died, the works were
>divided, and the Sports Optics division became independent.

We are particularly interested in the following glass specifications.

BSC 510644
BSC517642
DF620362
DF623360
EDF648338
EDF651336
EDF700303


Thank you

kamal Pant

>I would like to know why glass and not other synthetic materials
>are used to make photographic lenses.  All manner of input will
>be appreciated.
>
>Robert J. Triffin
>[email protected]

>        I am finding this discussion very interesting in light of the
>fact that a camera salesman I was speaking to last week strongly
>maintained that Schneider has had a serious problem, well known for years
>in Germany (where the salesman is from), with maintaining colour
>consistency in their lenses.  He claimed that the problem has arisen
>because Rollei, unlike Zeiss, is reliant on other makers for their glass,
>and implied that that might be the reason why Rollei has discontinued
>using S-K lenses.  I wasn't too inclined to believe him - though I think
>he believed what he was saying - given what I have heard in this group,
>but I wondered if anyone had heard this claim before.
>
>
>Gary Toop

> Once I get my doublet all designed with the lens design
> program that I have yet to find, where do I buy the glass
> blanks with the Schott 6 digit numbers?

United Lens Co., Inc.
259 Worcester St.
Southbridge, MA 01550-1325
Phone: 508/765-5421
Fax: 508/765-0500

------------------------

Glass Fab, Inc.
P.O. Box 1880
Rochester, N.Y. 14603
Phone:(716) 262-4000 Fax: (716) 454-4305
http://www.glassfab.com/

Schott Glass Technologies, Inc
400 York Avenue
Duryea, PA 18642

you wrote:
>>What we discovered in our tests for flatness and parallel faces
>>was that price had little relation to quality, with some cheap
>>filters equalling or bettering some expensive ones.  Hoya makes
>>filters under their name and also makes the filters for Japanese
>>camera makers like Nikon, Canon, Minolta, Contax, etc.

>Right.  Also, I've seen blanks being unpacked from Tamron boxes in
>German optical companies.  It makes no sense to ship Schott glass
>of ordinary types to Japan to make filters.  Hoya is one of the
>world's largest glass makers, so I doubt they use glass made
>by ANYONE else.

>ANy opinion on the Romanian IOR Valdor binoculars?  They claim that they
>use the same glass as the Zeiss Jena glass: Schott glass.  You can type
>in their name on the Internet Search  engine and read what they are
>stating about their East German connection regarding thier binoculars.

> My understanding, from Erwin if I recall correctly, is that no  production
> glass, in any Leica lens, uses a proprietary glass formula.

>  Bill Tuthill [email protected] wrote:
>
> >Minolta has been running advertisements lately pointing out that
> >they are one of only two "camera manufacturers in the world" who
> >make their own glass.
> >
> >Is the other one Nikon?  I'm wondering whether one company makes
> >all the glass for Canon, or whether it is multisourced.  Cosina
> >manufactures glass for the many lenses that they outsource, right?
> >I believe Zeiss (mostly in Japan) manufactures glass, but they
> >are not a camera company.
> >
> >(Not that it really matters who makes the glass, as long as the
> >lenses perform well.)

> Pentax, Sigma, Tamron, [not Minolta] and Canon all get their glass
> from Hoya (Tokina too, but as Hoya owns Tokina that's obvious).

> Leica and Nikon (not sure about Canon) make their own glass; but they do it
> by contracting the actual manufacture by another company (sub-contracting).
> Of course, the manufacture is handled to their exacting specifications...
> and they assemble the lenses themselves (i.e, gluing the elements together,
> mounting them, testing them, etc.).

> Zeiss does not manufacture glass.  It's Schott (which is owned by Zeiss)
> that makes their glass.

> Carl Zeiss is also a huge company. They manufacture their own lenses
> (although the glass generally comes from sister-company Schott). Zeiss has
> production facilities in Japan, where they make lenses which fit onto
> (Kyocera manufactured) Contax bodies, Contax and Yashica point-and-shoot
> cameras, Sony camcorders (a competitor of Kyocera's), etc.

>With all due respect, maybe you are right.  I had done research on glass
>melting and have letters from several Japanese optical companies that
>indicated when they started making glass.

> From: "Kotsinadelis, Peter (Peter)" [email protected]
> Reply-To: [email protected]
> Date: Tue, 23 Jan 2001 
> Subject: RE: [Rollei] gettn kinda Leica-OT What is it with the 25mm Focal
> length
>
> You are right Eric.  And Cosina also makes their own glass as do Konica,
> Minolta, Nikon, and Canon.  Pentax uses Hoya glass.

> Another big manufacturer (or the other one, there might be only a few in
> the world) is Dow Corning. I've read that Leitz lenses are made from Dow
> Corning raw glass.

> From: "Austin Franklin" [email protected]
> Date: Wed, 20 Jun 2001 
> Subject: RE: [CONTAX] Contax 645
>
>> All of the 645 lenses are new designs.
>
> I assume you really don't mean design in the optical sense, a Planar IS  a
> Planar design...from what I understand, and that design has been around  for
> quite some time.  Of course they are new in and unto themselves, in that
> these lenses are designed specifically for the 645.

>> The optical glass types available
>> from Hoya, Tamron, etc., in Japan differ slightly from those
>> available from
>> Schott, so the lenses were designed to be manufactured from
>> Japanese glass.
>
> What difference would that make?

>> Some of the designs for Hasselblad lenses are quite old and have not  been
>> updated, so it is no surprise that these newer ones are better.
>
> Could you define what you mean by better, and say why they are better?

> There may be nothing wrong with older optics designs, in fact, some  lenses
> designed 50 years ago have been unable to be improved upon.  Leica has
> updated it's lense designs over the years. and some of them have gotten
> worse!

> From: Javier Perez [email protected]
> Date: Fri, 08 Jun 2001
> Subject: Re: [russiancamera] grind lens surface
>
> I'm not sure but I think softer glass is considered
> better optically than hard glass.

> From: muchan [email protected]
> Date: Tue, 19 Jun 2001
> Subject: Re: [CONTAX] Contax 645
>
> 80mm Planar for Hasselbrad is f2.8, for Contax 645 is f2.0, they are  surely
> different design, aren't they? I think 120 Makro Planar for Contax 645  was
> also a new design. I think newer design has same Principe of design like
> G lenses. Contax 35mm MF lines are mix of old and new designs.
> New Zooms for N1 are with "new" thinking, reported to be like G lenses.

> From: "Simon Lamb" [email protected]
> Date: Tue, 19 Jun 2001
> Subject: Re: [CONTAX] Contax 645
>
> It would be very intersting to ask Zeiss whether they are providing
> different glass to Contax and Hasselblad, especially as you say that  clarity
> and contrast are markedly different.  Is the construction of the  equivalent
> lenses (say the 120 Makro Planar) the same or do Kyocera and Hasselblad  take
> the glass and make the design different?
>
> Simon

> From: "Kelvin" [email protected]
> Date: Wed, 6 Jun 2001
> Subject: Re: [russiancamera] J11 v.s. J11
>
> I mean, as in the materials used to make the glass e.g.
> fluorite glass, thorium glass etc. etc.
> Would different materials not have diff. refractive indicies?

> From: Lucian Chis [email protected]
> Date: Tue, 23 Jan 2001 
> Subject: Re: [Rollei] gettn kinda Leica-OT What is it with the 25mmFocal
> length
>
> I remember Erwin replied and said that it was still glass, but just  pressed
> together in those aspherical molds and without polishing (or with  minimum of
> that).
> The average LUGger was just terrified that their investment in an ASPH  lens
> would
> go down the yellow drain in 10 or 20 years..
> So, I'll look for my post on the subject and let you know.

> From: " " [email protected]
> Date: Tue, 23 Jan 2001
> Subject: Re: [Rollei] gettn kinda Leica-OT What is it with the 25mm
> Focallength
>
> A friend told me that Leica was involved with Corning of France in
> the development of molded aspherics,or, as Leica,I believe calls it,
> blank pressing. Is this true, as far as the company is concerned?

From Minolta Mailing List:
Date: Mon, 20 Aug 2001
From: "Kent Gittings" [email protected]
Subject: RE: Re: What is APO

Correct. The term is Low Dispersion glass (that's what LD comes from). The
lower the dispersion amount the closer it bends all the colors within the
visual range, about 400-750nm. The glass is rated by a number called the
Abbe ratio. This is a number based on a value of 0 to 1 with one being the
perfect zero dispersion of white light. Currently, I think, the closest to
one a non-synthetic optical element is around .93. This may actually be what
is called Flouro-crown glass, an optical glass used in several mid-priced ED
or Extra-Dispersion 2 element telescopes. As opposed to an artificial
crystal like Calcium Fluorite which is even closer to 1.0 than the best
glass but is more fragile.

Kent Gittings 

From: "Joe Codispoti" [email protected]
To: "Q.G. de Bakker" [email protected], [email protected]
Subject: Re: Non Hasselblad Advice From Contax Users
Date: Wed, 15 Aug 2001 

From: "Q.G. de Bakker" [email protected]>

> The Zeiss/Contax lenses might even be better than the Zeiss/Hasselblad
> lenses.

It might very well be. In 1993 Zeiss introduced a new type of glass (the
designation for it escapes me). The Contax-G lenses are produced with this
type of glass. No doubt the 645 also has the new formulation in its lenses.
I am sure also that the newly designed Hassy lenses also are of the same
generation glass.

Joe


From: "Andre Oldani" [email protected]
To: [email protected]
Subject: AW: Non Hasselblad Advice From Contax Users
Date: Thu, 16 Aug 2001 

I'm not a specialist but I think it's called simply "Neu-Glas" (new glass).
The Contax G-lenses, the 645 and the N1 lenses are equipped with that for
what I read. Has something to do with lead free material, fluor-cron-glass
etc. etc.

Andre

> -----Urspr=FCngliche Nachricht-----
> Von: Joe Codispoti [mailto:[email protected]]
> Gesendet: Donnerstag, 16. August 2001
> An: Q.G. de Bakker; [email protected]
> Betreff: Re: Non Hasselblad Advice From Contax Users
>
> From: "Q.G. de Bakker" [email protected]
>
> > The Zeiss/Contax lenses might even be better than the Zeiss/Hasselblad
> > lenses.
>
> It might very well be. In 1993 Zeiss introduced a new type of glass (the
> designation for it escapes me). The Contax-G lenses are produced with this
> type of glass. No doubt the 645 also has the new formulation in
> its lenses.
> I am sure also that the newly designed Hassy lenses also are of the same
> generation glass.
>
> Joe


Date: Fri, 31 Aug 2001 
From: ralph fuerbringer [email protected]
Subject: Re: A new panoramic camera from China
To: [email protected]

 if hoya doesnt make the glass for leica asperics  why wasnt there a single
peep when that was posted on the leica list? the leica list is the most
volatile list in cyberspace.  beside it the panorama list is civil
sleepwalking accept for a widelux wakeup call. german glass? what german
glass? for all practical purposes there is no german glass. there is only
the trickle used by zeiss themselves from the famous schott works who once
supplied everyone with rare earth glass including lanthanum.  schneider had
to reformulate the
famous 5.6 super anglulaon and discontinue the ultimate medium format normal
lens the xenotar altogether as it could not be reformulated.
why?  for a tax writeoff,the schott glass works was diminished to a shadow
of itself. Zeiss also discontinued all 45  and larger format lenses, the
contarex and a host of other cameras made by them and their newly acquired
voightlander. these couldnt compete with japan. They maake hasselblad lenses
and  that's about it now. it is common knowledge that the far east is the
source of  the new glasses evident in zoom and lenses such as the famous
german firm rodenstock's apo-gradagons. With little change in a forty year
old construction the 35mm covers more than twice the famous 38 biogon with a
shift yet. the new glass come from the far east, Korea and
japan. who knows how they they get this sensational glass? some one
suggested they melt down old saki bottles aged for a time in a volcano.

> From: [email protected]
> Reply-To: [email protected]
> Date: Fri, 31 Aug 2001 
> To: [email protected]
> Subject: Re: A new panoramic camera from China
> 
> That came as a suprise???
> According to Leica, their lenses are German Glass, and formulated by Leica to
> their own formula....
> 
> In a message dated 8/30/01 9:58:54 PM, [email protected] writes:
> 
>  hoya in japan is phoenix according to google. they make the glass for the
> leica ashperics and probably supply a significant portion of optical glass
> worldwide. ralph >>




From: [email protected] (brian)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: no new glass like the old glass, pollution lead was Re: old leica
Date: 26 Nov 2001 

Hi Bob:

I haven't been following the earlier thread, but I can say that it is
possible to replace lead with titanium in flint glasses to reproduce
all of the optical properties exactly (index, dispersion, and partial
dispersion).  The only differences are weight (the titanium flints are
much lighter) and toxicity (lead flints are more hazardous).  The
problem is not glass chemistry but economics of the optical glass
industry.  For years now there has been a push from the glass makers
and some less enlightened folks in the optical industry to reduce the
number of optical glasses available.  I think the military is largely
to blame here.  Its possible to buy a custom designed glass having
almost any property you want within the outer limits established by
glass research over the years.  Unfortunately, the glass catalogs only
have a finite number available for ordinary photographic use.  A
number of glasses that I have used in the past are no longer
available, and it is not because those glasses are toxic.

Brian


[email protected] (Robert Monaghan) wrote...
> Zhang makes a good point, which I'll reformulate to whether we could make 
> lenses with the same characteristics as in the past. 
> 
> You probably expect me to say YES, and that with the right glasses and 
> curves and design tradeoffs as used in the past, we can make them today.
> 
> But I suspect the answer may increasingly be NO, because the older glasses 
> used lead and other elements which are "environmentally" unfriendly, and 
> so are being phased out. 
> 
> A good example is the new formula hasselblad superwide 905, which uses 
> environmentally friendly (meaning different elements, less lead..) 
> glasses. The new lens is actually lower, based on MTF tests by the mfgers
> than the older lens, which most of us would say is a step backward 
> optically. 
> 
> So to this interesting question, I have to say, it is better and probably 
> lots cheaper to get that special "3-d" (from uncorrected spherical 
> aberrations etc.) "plastic" effect by buying older lenses and bodies they 
> can work with now, than to see if similar lenses will be made by the 
> mfgers in the future. It may be that the Nikon Defocus control series and 
> similar variable optical aberration control lenses can be used as direct 
> replacements, but I suspect many purists (e.g., many leicaphiles using the 
> older LTM lenses) would argue that the resulting imagery is due to the 
> unique combination of factors inherent in the older glasses and lens 
> designs. The new glasses make different compromises and optimize 
> differently, as I have heard other Leica types comment on the new vs older 
> Leica/Leitz optics, yes? 
> 
> just an interesting if rarely considered issue... bobm


From: [email protected] (Richard Knoppow)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: 105mm f/3.7 Ektar - Heliar
Date: Mon, 21 Jan 2002 

"william mitchell" [email protected]> wrote:

>Thanks for the Info.  I also have a Symmar-S/MC.  Will try to check it out
>against the Ektar.
>

  It will be interesting to hear what the differences are. The Ektar
is a very good lens but it doesn't have the coverage of the Symmar by
quite a bit.

  Kodak had the advantage of making its own glass and was the pioneer
in commercial development of the rare earth glasses developed at the
U.S. National Bureau of Standards. While its been suggested that
Zeiss- Schott developed such glasses during the early to mid thirties
there is no question about the work done at the NBS at about the same
time. These glasses were first used commercially around 1939 or 1940
at Kodak. Lanthanum and similar glass must be melted and refined in
pure Platinum lined pots so the procedure is not cheap. 

  The high index with low dispersion of these glass types considerably
expanded the choices lens designers had, making possible lower
aberrations and better color correction. 

  However, from the patent data available its uncertain if Kodak used
these glasses in the early Ektar series. I will have to look at
Altman's patent again to see if it specifies Lanthanum glass. 

  They certainly did very careful design and had excellent
manufacturing QC, at least during the time Rudolf Kingslake ran the
optical department (roughly 1938 to 1961). 

  I wonder what sort of lenses Kodak would have made using the Plasmat
type, which is the basis of most modern LF and enlarging lenses. They
made some supberb Planar types for the Ektra camera and later for a
Leica clone made for the military. 

  The early Hasselblad lenses are Kodak Ektars of similar design to
Altman's Heliar type above. 
---
Richard Knoppow
Los Angeles, CA, USA.
[email protected]


Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Does lens glass "flow?"
From: [email protected] (Dawn Yancy)
Date: Tue, 22 Jan 2002 

Jaan Peets [email protected]> wrote:

> Actually, at ambient temperatures, I believe that glass is a liquid

That is incorrect:

http://www.urbanlegends.com/science/glass.flow/amorphous_solid.html
http://www.discover.com/oct_99/physics.html
http://www.ualberta.ca/~bderksen/florin.html
http://www.glassnotes.com/WindowPanes.html



From: [email protected] (brian)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: retrofocus Leica M lenses prejudices was Re: leica M weight
Date: 6 Dec 2001 

Bob:

Low-volume (production volume, not size) glass aspheric elements can
be absurdly expensive.  High volume glass or plastic can be
surprisingly reasonable because the tooling costs are much less
prohibitive.  Aspherics are used in many consumer lenses because the
volume permits it.  Most consumer digicam lenses use aspheres, as do
lenses like the Nikkor 24-120 zoom.  Some of these aspheric elements
are plastic or a thin layer of aspheric plastic on a spherical glass
substrate, but many are 100% glass.  Its rare to see a lens design in
the patent literature these days that doesn't have one or more
aspheric surfaces.

Brian


[email protected] (Robert Monaghan) wrote 
> 
> I keep hoping that new techniques will make aspherics less pricey, rather 
> than 10x the cost of simpler to make elements, so they could be used more 
> widely...
> 
> regards bobm


From: "Q.G. de Bakker" [email protected]
Newsgroups: rec.photo.equipment.35mm
Subject: Re: retrofocus Leica M lenses prejudices was Re: leica M weight
Date: Fri, 7 Dec 2001 

brian wrote:

> Low-volume (production volume, not size) glass aspheric elements can
> be absurdly expensive.  High volume glass or plastic can be
> surprisingly reasonable because the tooling costs are much less
> prohibitive.  Aspherics are used in many consumer lenses because the
> volume permits it.  Most consumer digicam lenses use aspheres, as do
> lenses like the Nikkor 24-120 zoom.  Some of these aspheric elements
> are plastic or a thin layer of aspheric plastic on a spherical glass
> substrate, but many are 100% glass.  Its rare to see a lens design in
> the patent literature these days that doesn't have one or more
> aspheric surfaces.

Yes. The first mass produced, cheap aspherical lens was the
lens mounted in Kodak's 1982 Disc camera (remember that
thing?).

But many of the current asphericals are molded, not ground.
Not quite the same quality. And even if they are ground,
modern CNC machines can easily produce aspherical surfaces
within a toleance of less than 0.5 micrometer. Very
impressive. But still a factor 10 above the lamda/4
tolerance that is needed in quality optics.



From: [email protected] (brian)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: retrofocus Leica M lenses prejudices was Re: leica M weight
Date: 7 Dec 2001 

Q.G.:

The biggest problem I've encountered with aspheric lenses is tooling
marks that create havoc with flare.  Molded glass lenses can really be
quite good, although the tooling costs are pretty shocking. 
Photographic optics do not require an overall surface accuracy of 1/4
wavelength.  The tightest tolerance generally used by the best makers
is around 1-2 waves of power and 1/2 wave of irregularity.  Far looser
tolerances are often fully adequate, especially for large aperture
systems that are far from diffraction-limited.  Tilt and decentration
are always far more important to control than surface figure in
photographic lenses.

By the way, the Kodak disc camera lens was actually excellent, and was
capable of resolving well beyond 200 cycles per millimeter even in the
corners. (I can send you a reference if you want)  The film on the
other hand . . .

Brian
...


From: [email protected] (Heinz Richter)
Newsgroups: rec.photo.equipment.35mm
Date: 08 Dec 2001 
Subject: Re: retrofocus Leica M lenses prejudices was Re: leica M weight

>Photographic optics do not require an overall surface accuracy of 1/4
>wavelength.  The tightest tolerance generally used by the best makers
>is around 1-2 waves of power and 1/2 wave of irregularity.
> Tilt and decentration
>are always far more important to control than surface figure in
>photographic lenses.

I can only speak for Leica here.  Their tolerances are as follows:
Lens thickness - 10 microns
Sphericity - 3/100 micron
Centering - 4 microns


Heinz
GMP  Photography
FOTOgraphicART
GMB Custom Black & White Lab
http://www.goldmem.com


From kiev mailing list:
Date: Fri, 14 Dec 2001 
From: Kevin Kalsbeek [email protected]
Subject: Re: Lens Bubble?

Eric,
The bubble in the Flektogon with hurt nothing!! Forget it!  Many years ago,
lens bubbles were very common until a Japanese engineer in the early 1950's
came up with a special crucible the virtually elimated them.

A bit of dust will hurt nothing either!!
Kevin


from nikon mailing list:
Date: Sat, 19 Jan 2002 
From: Michael Briggs [email protected]
Subject: RE: Green glass

[email protected] wrote:
>    From: "John Owlett" [email protected]
> Subject: Green Glass

cut....
> http://www.2filter.com/faq/facts.html
>
> The author seems to me to be negative about the quality of "green
> glass" for filters.
>
> (1)  He or she is another enthusiast for B+W, saying (among other
>      things), "No B+W filter has ever been made with green glass, and
>      they never will, I hope."
>
>
> (2)  He or she says of Hoya filters, "We do not carry the least
>      expensive type called the EXCEL (XL) Green Series, because
>      they are made with a type of glass known as green glass.   The
>     filters are clear when you look through them, but from the side
>     (edge) you can see a green tint in the glass....

cut...

> Does anyone know more about green glass?  The phrase is new to me.

Green glass is merely glass of the same grade as common clear glass such
as window glass.  If you look at the edge of window glass you will see a
blue/green tint.  If you look carefully through a piece of thicker glass,

you can also see this tint.  The human visual system is excellent at
ignoring shifts in white, so normally we don't notice this.  Before I
switched to using UV-absorbing acrylic (Acrylite OP-3) for framing photos,
I was concerned that a slight yellow cast might be present from the UV
absorbing dye.  Then I compared a piece of UV-absorbing acrylic laid over
a B&W photo to a piece of window glass.   

The difference was surprising: the plastic appeared clear and
the glass had a definite color tint.  (The other important differences are that
the plastic is almost unbreakable compared to the glass, but scratches
much easier.)


The blue-green color is caused by very slight contamination of the glass
with iron.  Optical glass has to be made from purer ingredients than are
used for common window glass, consequently optical glass, even if made
with the small chemical ingredients as window glass, costs more.
However, the cost difference in a filter is rather small because the glass
quantity is so small. Using window glass in a photo filter is evidence of
cost being far more important than quality. It doesn't make sense to pay
the premium for a genuine Nikon lens and than to put a green-glass filter
in front of it. I rather like the B+W quality quote above.  That said, a
thin green glass filter won't cause much of a color shift.


--Michael



From camera makers mailing list:
Date: Tue, 04 Jun 2002 
From: William Nettles [email protected]
Subject: [Cameramakers] Glass Negs

---William Nettles

[email protected]
Nettles Photo / Imaging Site  http://www.wgn.net/~nettles

>
> A critical part of this whole process is the selection of the glass. It is
> _not_ advisable to
> reclaim old glass plates, at least if they have a developed image. The silver
> seems to be
> absorbed or adsorbed by the glass, leaving sites that will cause a subsequent
> image to appear in
> subsequent development.

Ohhhh The ghost baby photos in the Wisconsin Death Trip book. Very
mysteriouso very creepy.

> I have heard more recently of a clever technique which uses a large vessel of
> molten tin. The
> molten glass is poured on it, where it has a chance to flow out into a uniform
> thickness before

This has been the standard glass making procedure for some years now. I
think all common window glass is now made this way. Finding old wavvy glass
is difficult and expensive.

One thing we learned shooting booze pour shots that was confirmed later by
knowledgeble sources is that if you clean off glass it begins to get pitted.
We found that expensive crystal wine glass soaped rinsed and wiped clean by
even the softest of cloths began to get noticably pitted and marked after a
several washings.  This glass may be soft. But any glass after several
cleanings soon loses its 'new' look. I don't know how this would affect
glass negatives.

Also, according to Scientific American, glass breaks 27 times more easily in
the presence of water than when it is dry. This doesn't mean your windshield
is going to explode in a rain storm. Glass shops for years would wet down
the etched scribe line before snapping off a section of glass. After reading
the article I saw a glass guy doing this and asked him why he did it. He
said he was told it would make the cutter last longer.

Oil doesn't work. The water molecules enter the crack. Glass is esseentiall
a latice of silicon atoms connected by shared oxygen atoms. Under the stress
of a forming crack the silicon atoms are trying to pull apart but they don't
want to let go of their oxygen atom. Oxygen atoms from the water molecules
joins onto one of the silicon atoms eleviating its need to share an Oxygen
and the glass breaks.  Oil won't work according to the article because the
hydrocarbon molecules are too large to slip deep enough into the crack.
I don't know why atmosperic oxygen won't work.


From camera makers mailing list:
From: John [email protected]
Subject: Re: [Cameramakers] Glass Negs
Date: Wed, 05 Jun 2002 

...

        Just a little experience. We use lighter fluid on framing glass.
Don't know why but the cuts are cleaner.

Regards,

John S. Douglas - Photographer, Webmaster & Computer Tech
        Website --- http://www.darkroompro.net


From contax Mailing list:
Date: Mon, 9 Sep 2002 
From: "Wing S. Yu" [email protected]
Subject: Re: [Contax] Talking of D35/1.4 (was May I crow?)

I have checked the Zeiss web site and surprisingly Zeiss used many
Fluor-Crown elements in CONTAX lenses now. The N24~85 and N70~300 both have
Fluor-Crown elements.

Here is what Zeiss says about the 24~85:

"To achieve this high image quality along with relative compactness, this
lens uses elements made of special fluor-crown glass with anomalous partial
dispersion, and additional aspheric surfaces."

Wing
...


From: [email protected] (Steve Hamley)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Digital - Boom in medium format? Was: Re: Used Medium format...
Date: 4 Sep 2002 


Ralf,

Interesting comment, and possibly true. I have heard that lens
companies are phasing out lead in optical glass because of
environmental concerns - not that anyone believes the landfills are
going to end up full of LF lenses. Heck, most of the ones from the
1920s are still around taking photographs. Anyway, I've also hard that
reformulating the glass means reformulating the design, which makes
sense.

According to posts on the LF forums, both Schneider and Rodenstock
have dropped models of their repro lines, namely the G-Clarons and the
barrel-mount Apo-Ronars. One of the reasons speculated on is that they
didn't want to reformulate these lenses since most repro work is going
digital.

If the above speculation is true, and the newly intoduced Super Symmar
XL aspheric series doesn't use the dreaded lead, I'd look for these
lenses to replace other Schneider wide angles. These lenses have been
a great success, especially the 110mm Super Symmar XL. I have the 80mm
f/4.5 version, and it's amazingly bright, suffers less from falloff
than others, better up close, and is smaller and lighter to boot.
People who backpack have replaced both a 75mm and a 90mm with this
lens. Schneider did their homework on these and I suspect they will
replace some other Schneider wide angles by popular demand.


Thanks!

Steve
[email protected]

[email protected] (Ralf R. Radermacher) wrote 
> Robert Monaghan [email protected] wrote:
>
> > I'd
> > bet the cost of LF kits is lowest, since so many get by with one lens or
> > at most two, and often use older press graphic or view cameras that are
> > very cheap, few new camera sales and new lens sales even fewer too
>
> Just overheard some talk today that Schneider are seriously reducing
> their choice of LF lenses, especially at the wide angle end.
>
> Ralf



From: [email protected] (brian)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Canon UD and Fluorite elements?
Date: 8 Oct 2002


"Max Perl" [email protected] wrote...
> Aha.....
> Do you know what glass Nikon uses in their 105mm UV lens?
> Would they have any benefit of using flourite glass in this lens?
> Do you think Carl Zeiss uses flourite glass in their super archromats?
>
> Max

Max:

The Nikon UV lens is discontinued, but it was made from fused silica
and fluorite.  These are the only two practical materials that are
transparent into the deep UV.  Fortunately, they can be combined to
achieve a wide-band apochromat ranging from about 250nm in the UV all
the way to about 650nm (red) in the visible.

I'm not familiar with the Carl Zeiss super apochromat you mention, but
if it is intended for true UV below 350nm then it undoubtedly uses the
same two materials.  For ordinary visible apochromats I imagine that
Zeiss uses either Schott FK  or Hoya glasses.  In fact, the last time
I visited Zeiss in Jena I was surprised to find out that they
preferred Hoya glass because of reduced cost!

Brian



From: "Max Perl" [email protected]
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Canon UD and Fluorite elements?
Date: Tue, 8 Oct 2002


Hoya glass?.....It was my impression that Zeiss made their own glass from
scratch. Hoya makes good filters so why not.......
The filters which are branded with Hasselblad looks very much like Schneider
K. /B+W filters. Probably there are not many glass manufactors. It could be
fun to have a list of which brands made their own glass.

Max
...


From hasselblad mailing list:
From: Jim Brick [[email protected]] 
Sent: Sat 5/24/2003
To: [email protected]; [email protected] 
Subject: Re: [HUG] A new Lens for the V-System

All production Leica camera lenses are manufactured from glass purchased
from other companies. Schott and Hoya being the two main suppliers. Leica
has a glass lab, but it is very small incapable of manufacturing enough
glass for even one line of lenses. All Leica glass is off-the-shelf catalog
glass from major glass companies. What sets Leica lenses apart from other
lens manufacturers is the optical formula, not the glass formula.

Jim

Anthony Atkielski wrote:
>I haven't heard anything from Leica about this, so I presume that their
>engineers are still free to do things correctly.


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[Ed. note: page was at http://www.f32.com/Articles/art002.htm  3/2003]