EV Exposure Values for Photographers

EV Exposure Values for Photographers

Related Links:
EV and LV (Ken Rockwell) [9/2002]
EV and Shutter Speeds.. [8/2001]
EV and Shutter Speeds (Fred Parker)[2/2002]

Michael Gudzinowicz gives a very short and cogent explanation of EV numbers in the post below. These EV numbers are most commonly encountered on some higher end leaf shutter lenses found on Rolleiflex Twin Lens Reflex and Hasselblad lenses, among others.
These lenses offer an EV-coupled setting, usually with a release lever to change EV values as needed or select uncoupled operation (aperture and shutter speed set separately). Each shutter speed is matched to the same EV value setting by the corresponding aperture. The user can select the desired shutter speed, and the aperture is automatically properly set by this EV coupled setup.
Works great in daylight or daytime shade conditions, where the light levels don't vary significantly. You can shoot faster too, since you only select the aperture or shutter speed you need. The other value is automatically coupled and set for you.

rec.photo.misc
From: [email protected] (Michael Gudzinowicz)
[1] Re: Photo MATH Challenge (not for the weak!)
Date: Sat Sep 05 1998
Roger Bergeron [email protected] writes:

>I'm interested to know if anybody actually knows 'THE' formula used by >exposure meters. I am trying to create one that results in 'E.V.' units. > >No easy task!!! Does anybody know of one?

The EV formula is simple - it simply provides shutter speeds and apertures which give equivalent exposures.
For example, if a speed/aperture combination such as f/11 @ 1/250 sec is given, the EV number is the sum of the reference numbers given in the table which follows. The reference number for the aperture (f/11) is 7 and the that for the speed (1/250) is 8. The EV number for the combination is the sum, 15. Any combination of reference numbers for the speed and aperture whose sum is 15 will give the same exposure. For instance, a speed of 1/15 (#4) requires an aperture corresponding to the reference number 15 - 4 = 11, or f/45. Likewise, an EV of 9 requires a sum of 9 - f/5.6 @ 1/15 works, as well as f/1.4 @1/250, etc.

Reference Speed Aperture Number (sec) (f/stop) 0 1 1 1 1/2 1.4 2 1/4 2 3 1/8 2.8 4 1/15 4 5 1/30 5.6 6 1/60 8 7 1/125 11 8 1/250 16 9 1/500 22 10 1/1000 32 11 1/2000 45 etc...

It should be apparent the the recommended EV for an exposure reading will depend on film speed. For instance, the recommended EV for 400 speed film will be two numbers greater than that for 100 speed film (2 stops less exposure). One can interpolate fractional EV values for exposures which don't fall in one stop increments.

rec.photo.misc
From: [email protected] (Michael Gudzinowicz)
[1] Re: Photo MATH Challenge (not for the weak!)
Date: Sat Sep 05 1998
Michael Gudzinowicz [email protected] writes:
>Roger Bergeron [email protected] writes: > >>I'm interested to know if anybody actually knows 'THE' formula used by >>exposure meters. I am trying to create one that results in 'E.V.' units. >> >>No easy task!!! Does anybody know of one?

I should have included the description of how EVS values are determined from light readings and film speed. One adds the light value corresponding to the footcandle reading in the table on the left to the additive speed given for different EI values. The sum is the EV number, which corresponds to the speed aperture values given below in the qoute of my previous post.

Footcandle LV EI Additive Speed 6 0 3 0 12 1 6 1 25 2 12 2 50 3 25 3 100 4 50 4 200 5 100 5 400 6 200 6 800 7 400 7 1600 8 800 8 3200 9 1600 9 6400 10 3200 10 If you derive the formulas relating footcandles, LV, EI, additive speed, EV, f/stop and speed, it simplifies to the following equation: (f/stop)^2 fc * EI ---------- = ---------- speed 25 >The EV formula is simple - it simply provides shutter speeds and apertures >which give equivalent exposures. > >For example, if a speed/aperture combination such as f/11 @ 1/250 sec is >given, the EV number is the sum of the reference numbers given in the >table which follows. The reference number for the aperture (f/11) is 7 >and the that for the speed (1/250) is 8. The EV number for the >combination is the sum, 15. Any combination of reference numbers for the >speed and aperture whose sum is 15 will give the same exposure. For >instance, a speed of 1/15 (#4) requires an aperture corresponding to the >reference number 15 - 4 = 11, or f/45. Likewise, an EV of 9 requires a >sum of 9 - f/5.6 @ 1/15 works, as well as f/1.4 @1/250, etc. > >Reference Speed Aperture >Number (sec) (f/stop) >0 1 1 >1 1/2 1.4 >2 1/4 2 >3 1/8 2.8 >4 1/15 4 >5 1/30 5.6 >6 1/60 8 >7 1/125 11 >8 1/250 16 >9 1/500 22 >10 1/1000 32 >11 1/2000 45 >etc... > >It should be apparent the the recommended EV for an exposure reading will >depend on film speed. For instance, the recommended EV for 400 speed film >will be two numbers greater than that for 100 speed film (2 stops less >exposure). One can interpolate fractional EV values for exposures which >don't fall in one stop increments.

rec.photo.misc
Date: Sat Sep 05 1998
From: [email protected] (Rudy Garcia)
[1] Re: Photo MATH Challenge (not for the weak!)
Roger Bergeron [email protected] wrote:

> I'm interested to know if anybody actually knows 'THE' formula used by > exposure meters. I am trying to create one that results in 'E.V.' units. > No easy task!!! Does anybody know of one?

You might try this one:
footcandles * seconds = (25 * fstop ^2) / ISO
Although how you get from it to EV units ??
--
Use address below for Email replies. Address on Header is bogus to defeat AutoSPAM.
[email protected]
Rudy Garcia

Date: Sun, 16 Aug 1998
From: Richard Urmonas [email protected]
To: [email protected]
Subject: Re: [Rollei] New Rollei owner with questions

> 1. On the shutter speed dial, what do the numbers on the face of this > dial represent.

These are the EV numbers. If you have a lightmeter with EV display you can make use of this. To use it turn the small knob in the centre of the aperature knob so that the line points to the circles. This locks the shutter and aperature dial together. To set the EV push the small knob on the aperature dial in. Now turn the shutter dial so that the small pointer indicates the proper EV. Releasing the small knob re-locks the dials. Now turn either dial to vary the aperature/shutter selection. If you do not use EV then make sure the small knob on the aperature dial is not lined up on the circles, this keeps the knobs unlocked. ....

From Rollei Mailing List:
Date: Thu, 24 Aug 2000
From: Matthew Phillips [email protected]
Subject: Re: [Rollei] re: first rolleiflex

>Now I'm really starting to feel dumb. I don't know what EVS is...

You really shouldn't feel dumb because you aren't up on 1950's technology.
The EVS designation that we've referred to was a product of the postwar move to incorporate exposure meters into cameras. Once shutter speeds became standardized in their current linear sequence, simple uncoupled meters began appearing in leaf-shuttered cameras, such as Rolleis, Retinas, Contaflex's; these settings still appear on Hasselblad lenses. The EVS (exposure value system) or LVS (light value system) was a numerical sequence that refers to light level: the higher the number, the brighter the light. For a given light level, or EV setting, a number of different shutter speed and aperture combinations give an equivelant exposure, i.e. 1/60@f/11 = 1/30@f/16 = 1/125@f/8, etc. It works alot like the program shift you find in modern electronic cameras. On cameras with an EVS coupling, after the EV is set, the shutter and aperture settings are linked. The advantage to this system was it made it simple to adjust depth of field or shutter speed while maintaining exposure.
Once this system is learned, it will frequently allow you to 'see' your exposure without resorting to a meter. Most of us tend to repeatedly shoot a given film speed under similar lighting conditions. If, for example, you are using TMax 100 on a bright day, your EVS setting will keep coming up between EV14 and EV15. Now you have a whole range of shutter and aperture combinations to work from, but the EV remains constant. Experience will quickly teach you how to dispense with a meter for many situations. The downside to this system is the extra learning curve, it sometimes gets 'in the way' of those who don't choose to use it, and that it makes bracketing cumbersome.
Regards,
M.Phillips

From Rollei Mailing List:
Date: Fri, 25 Aug 2000
From: Richard Knoppow [email protected]
Subject: Re: [Rollei] Re: EVS rolleis
you wrote:

>My lovely little garage sale Rollei has one very very nice feature I'd never >used before-- th exposure table on the back. It only goes up to ASA 100 (I >now use a lot of that speed) but the table can be used to get pretty close >to perfect exposures. > >I have meters, but tend to use the "sunny 16" rule (which ought really be >the "sunny 11" since "shutter speed-equals- film speed" seems to expose >better at f 11 in sun rather than f 16) and the EVS scale actually suggests >an aperture between those two settings. > >Anyway not schlepping a hand-held meter along makes stepping out of the car >or off he bicycle to snap an interesting scene a little faster. > >BTW it may be age, But all I need to do to override the EVS link is to hold >down the wheel I want to stay put while rotating the other one. > >This will probably break something some day.... But my camera does not seem >to have an inner button to hold to release the link...

FWIW, exposure charts can be quite accurate. The ISO method of measuring film speed yields the very minimum exposure which will give adequate shadow detail provided the scene matches the assumptions made by the system. The exposure may be too little for some scenes. Film has tremendous over exposure latitude so there is little, if any, harm in rating film at about half speed.
There is a long history to film speed measurement. Modern sensitometry started with Hurter and Driffield around 1890. they worked out the basic relationship between exposure and density which characterize sensitive emulsions.
The ASA system of speed measurement, and much of the understanding of tonal reproduction, stems from work done by Lloyd A. Jones, of Kodak Laboratories, who began to publish the results of his investigations in 1920 (in the Journal of the Franklin Institute). Jones, and his colleagues, conducted an extensive research into what made an "excellent" print. The judgement being made by means of a survey of hundreds of viewers, both professionals and naive viewers. The research resulted in a long article on the principles of tonal reproduction (I will find the citation for its original publication) which has been reprinted in somewhat shortened form in several textbooks, including Mees's famous text. The research also resulted in a method of determining the speed of B&W material. The system was initially put into practice as Kodak Speeds about 1940. Kodak Speeds are about twice the current ISO speeds.
When the ASA adopted this method of speed measurement (1943 and 1946) they included a 2.5X safety factor. Jones had intended give film the _minimum_ exposure which resulted in an "excellent" print. The reason for this is that thin negatives are less grainy and have better sharpness than denser ones. Jones original method was based on finding a specified minimum contrast (gamma) at the toe end of the film curve. This minimum gradient assured that there would be adequate shadow contrast in the image regardless of the shape of the toe. Kodak, in its film handbooks of the time warned that exposures of about half indicated should be tried and might be more satisfactory for some subjects. At the time development recommendations tended toward higher contrast, also to insure the presence of an image. The combination often resulted in dense, hard to print, negatives.
The minimum gradient method turned out to be too hard to measure in practice. In 1958 the ASA dropped the method in favor of the German DIN method based on a minimum shadow density rather than a minimum gradient. This method is much easier to measure in practice but does not account for the toe, or shadow, contrast. The DIN method is the basis of the current ISO method. At the same time as it adopted the DIN method the ASA dropped the safety factor. This had the effect of doubling all film speeds. This put several developer manufacturers out of business since they had been advertising their products could double film speed!
In any case, the current ISO method may result in speeds which are too low for some scenes so some increase in exposure will often produce better negatives.
----
Richard Knoppow
Los Angeles,Ca.
[email protected]

Date: 18 Jun 2001
From: [email protected] (dan)
Newsgroups: rec.photo.equipment.35mm
Subject: FYI: Exposure Value System Charts
These may be of interest to some of you.
Chart 1: Shutter Speeds at EV & Aperture
Chart 2: EV at Shutter Speeds & Aperture
http://users.ev1.net/~dbdors/Photography/ev_table.html
They are available as downloadable Excel spreadsheets or Text files here:
http://users.ev1.net/~dbdors/Photography/Photography.html
May the Light be with you.
-----
dan

Date: Tue, 1 May 2001
From: "Q.G. de Bakker" [email protected]
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: EV Table
Wilt W wrote:

> What I meant was, is there > any company that sells EV charts/tables in a simple card form (preferably > business card size, or a credit card size), that one can purchase for a > friend, who is a novice, so that she can carry in her camera bag? > > The 'problem' of making any EV table is that 1EV is simply representative of a > 'quantity of light on the scene' but NOT 'a combination of f/stop and shutter > speed'.

No it isn't.
It *is* the name/value given to an aperture/shutterspeed combination. EV1 is the same, no matter what speed film is used.
You can calculate what EV is the appropriate camera setting for any particular illumination level/filmspeed combination using:
EV = log(ISO * 0.32) / log(2) + log(Lux / 85) / log(2)
ISO stands for the film's ISO value, and Lux for the level of illumination in lux.
Yes, different film speeds and different lighting levels do result in different EV-values, but this changing EV simply is the appropriate EV-setting to get correct exposure. However, EV 1 remains EV 1 (f/1 at 1 sec shutterspeed, or any equivalent combination. By the way, notice all the "1"s in EV 1?).

Date: Wed, 02 May 2001
From: Dave Wyman [email protected]
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: EV Table
Try http://www.teleport.com/~bcat/guide.html
This is larger than a credit card, but as other have pointed out, EV numbers themselves are meaningless. I do know that EV 15 on my Rolleiflex meter with ISO 100 film means f/16 at 1/125 sec, but it gets hazy quickly with other ISO ratings and lighting conditions. The Black Cat extended guide, like an analog light meter, offers various shutter speed and f/stop combinations at a glance.
Dave Wyman
NoSpam wrote:

> Can anyone in this NG tell me if someone makes a decent EV table/chart for a > beginner photographer who has not yet mastered in memorizing the EV's? > > Thank you all in advance.

Date: Sat, 08 Sep 2001 To: [email protected] From: Dan Cardish [email protected]> Subject: Re: EV scale on lens EV has nothing to do with film speed. You can't have EV 15 being both f16 1/125 and f16 1/500 at the same time. In fact it just so happens that EV15 is equivalent to f16 @ 1/125, all the time, by definition. If a meter requires a camera setting of f16 1/500 then it is telling you that you need an ev value of 17. dan c. kwow wrote: >Yeap, Jim is right. I believe that the film sensitivity to light in terms of ISO rating will react different with the same EV, eg : for ISO 100, EV 15 will result in f16, 1/125, for ISO 400, EV 15 will result in f16, 1/500.
From: "Q.G. de Bakker" [email protected]> To: [email protected]> Subject: Fw: EV scale on lens Date: Sat, 8 Sep 2001 Jim Stewart wrote: > I am not wrong. Perhaps if you had the light meter in front of you, you > would understand. It's a Sekonic L-228. It has a meter scale with numbers > on it and a ring to translate the number to both fstop/shutter speed pairs > or EV numbers. If I set the film speed to 100, the scale numbers translate > exactly to EV numbers. Okay, So i'll take a meter too, set it up for ISO 100, and see (without doing anything else) that 1 sec at f/16, 1/2 sec at f/11, etc. are all opposite each other, and the EV scale shows EV 8. So now what? How would that be the correct exposure? (As a matter of fact (as is easily checked, since i'm holding a meter...) it isn't. It even isn't when i point the thing in the other direction. But of course, if i try hard enough, i could find a spot to point the meter that will say the correct exposure would be EV 8 ;-)) The problem with my meter, of course, is that it doesn't use intermediate numbers to 'translate' apertures and shutterspeeds to EV values. It just displays EV values as well. But yes, i do understand, you are talking about a peculiarity of your lightmeter's scales. But be careful, that does not mean that the EV system is based on ISO values. The EV system was setup as a shorthand system to describe shutterspeed-aperture combinations that all give the same amount of exposure. The root, EV 0, was quite arbitrarily, chosen to be f/1 at 1 second. It could just as well have been EV 1 (easier to remember, all 1's). There is no more to it than that. To calculate correct exposure we would not only need ISO vales, but LUX values as well. For all who want to do this, here's the formula: EV (giving the correct exposure at the chosen ISO setting and meassured Lux value) = log (ISO * 0.32) / log(2) + log(LUX / 85) / log(2) Or, perhaps more usefull to all who have a meter that will display EVs but not LUX: Lux = 2^(EV - (log(ISO * 0.32) / log(2)) * 85
From: "MAF" [email protected]> Newsgroups: rec.photo.equipment.medium-format Subject: Re: New to medium format Date: Sat, 24 Nov 2001 This camera does not contain a light metering system so an ISO setting would be meaningless. You must use a separate light meter and then adjust the shutter speed and aperture manually. If you don't want to use a light meter, you can run some tests and come up with a table of exposure settings for the film/developer combination you use in the various lighting scenarios that you normally encounter. Brett Weston did this and rarely used a light meter. Here is web site that may be useful to get you started. http://members.tripod.co.uk/Photoman/ETable.htm Remember to adjust for your ISO (ASA) film speed. But keep in mind that "bright sun" in Norway may be a different exposure than "bright sun" somewhere else, so it's best to run your own tests rather than rely on someone else's tables. If you are using filters for B&W photography (yellow, red, etc.), additional filter factors must be applied to these exposures. "Vidar Giljebrekke" [email protected]> wrote > I just bought my first camera that is completely manual, a Mamiya RB67 Pro > S. > There isn't even a setting for the film ISO, so I am wondering if there is > any exposure tables > or anything similar that can be helpful, when getting into this wonderful > camera, and medium format > photography :) > > Any help and advice is greatly apreciated > > Sincerely > > Vidar
From: "Q.G. de Bakker" [email protected]> To: [email protected]> Subject: Re: [HUG] Re: hasselblad V1 #1474 Date: Tue, 22 Jan 2002 Santiago Torres wrote: > I`m sorry for bringing an out of topic question, but it is really urgent for > me and I hope someone can help me. > I need to know if there is any way (formula?) to convert EV values into > luminance values (e.g. cd/m2) I need to use my puntual exposure meter to > mesure reflectances from samples. I think relative values wont work because > 0EV is not really 0.... Any help is most welcome. Thank you, Would EV to Lux be of any use to you? Lux = 2^(EV - (log(ISO * 0.32) / log(2))) * 85 Example: EV 12, ISO = 100 Lux = 2^(12 - (log(32)/log(2))) * 85 = 2^(12 - 5) * 85 = 10.880 The result is an approximation, but more than close enough.
From: "Q.G. de Bakker" [email protected] Newsgroups: rec.photo.equipment.medium-format Subject: Re: Hasselblad PME3 Meter Prism Finder Date: Mon, 3 Dec 2001 David Meiland wrote: > I'm pretty sure ALL Hassy lenses have the EV scale on them along with > shutter and aperture. Set the lens to the number in the finder. And i even am 100% sure all Hasselblad MF lenses have EV numbers on them. But, B.R. Norwall, tell us what kind of lenses you have (do they say "Synchro-Compur"? or "CF"?) and we can tell you how to use the EV scales. They make everything so much easier. You can tabulate the apertures and shutterspeed combinations that make up the Exposure Value numbers, starting with the knowledge (which already was given) that the combination of f/1 and 1 sec. equals EV1, plus the knowledge that every change to aperture and shutterspeed will change the EV an equal amount, i.e. changing either 1 stop will be equal to a change of 1 in EV. Last bit of info you need is that changing either towards less exposure (smaller aperture (=larger f/number) and shorter shutterspeeds) increases EV, changing them towards more exposure decreases EV. You can use formulae too: EV = log(aperture^2 / shutterspeed) / log(2) Shutterspeed = aperture^2 / 2^EV. (you have to use true shutterspeeds, for instance: 1/500 = 0.002. And it's even better to use true true shutterspeeds, shutterspeeds increase and decrease by a factor 2, so the true scale is 1/1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512, 1/1024, etc.) And, obviously, there is a link between filmspeed and amount of illumination. You can even calculate the amount of light in Lux starting with a given EV and filmspeed, and, vice versa, the EV to set given an amount of light in Lux and filmspeed. Here's how (fill in for filmspeed the old ASA part of ISO): EV = log(ISO * 0.32)/log(2) + log(Lux / 85)/log(2) Lux = 2^(EV - (log(ISO * 0.32)/log(2)) * 85.

From: Gary Frost [email protected] Newsgroups: rec.photo.equipment.35mm Subject: Re: Night photography shutter speed Date: Thu, 21 Feb 2002 Here's a site for you to look at: http://www.fredparker.com/ultexp1.htm Particular attention to the EV scale for estimating light levels in your low-light situations. Using a scale like EV (or how many stops below sunny 16) will simplify this kind of work whether you use a meter or not. ...one of the problems with in camera meters that have just a shutter-speed/stop readout: people have lost a simple method of accurately estimating actual light levels. Blindly following a readout or match-needle. Think in terms of EV, (normalized for ISO 100, sunny 16 is EV15) Your night/skyline exposures would be in the EV 1 to 5 range. You should also consider whether you use slide or neg film: the neg film should get more exposure (+1 stop). Good Luck. TC wrote: > > Hi, > > I would like to do some night photography on cityscapes, etc and would like > to know whether there are some guidelines on shutter speed and aperture > combination. For example, for photographing such and such you use this > shutter speed with this aperture for this speed of film, etc. > > What if my camera meter is too weak to meter at low light? What if I'm > photographing some light sources (lights from building?) This will, I > assume, will fool the meter and make my pictures underexposed. I have > searched the net and newsgroup and I still can't come up with an answer. > > Thanks. > > Toby.

Date: Fri, 24 May 2002 From: David Gerhardt [email protected] To: [email protected] Subject: Re: [HUG] HELP! PM45 Question... "Q.G. de Bakker" wrote: > you can lock both > shutterspeed and aperture rings together using the little button on the > right of the aperture scale. Since Daniel is going to shoot this wedding tomorrow (?!), a couple of other items he might want to be aware of: 1. The EV numbers on the LENS are in ORANGE, and on the same "ring" as the shutter speeds (at least on my CFE lenses); and the mark for "setting" the correct EV is a WHITE TRIANGLE on the lens (located on the same ring as the apertures), opposite the orange EV numbers. 2. On the CF/CFE lenses, the "button" that you push down to "lock" the selected EV is sometimes hard to push, and/or maintain locked. On my 80mm CFE, it's relatively hard to keep the button pushed down (to "select" the EV), and then ROTATE the aperture & shutter speed rings "together". (By the way, this "rotation" of the locked rings is how you change your shutter speed or aperture at the "metered" EV). 3. On the older "C" lenses, the "default" was that the EV was ALWAYS LOCKED, and you had to "tilt" one ring to DISENGAGE the shutter speed & aperture rings. Pretty much the opposite of the current (CF, CFE...) lenses. The older ( C ) lenses were EASIER to use in this respect (keeping EV "fixed"). I presume you have the newer "CF" lenses, and therefore have to exercise a little care when "locking" the lenses to change shutter speed (or aperture) while maintaining a constant value of EV. Be sure to check that it hasn't "slipped off" of your metered EV. Good luck! -- David Gerhardt [email protected]

From rollei mailing list: Date: Mon, 22 Jul 2002 From: Richard Knoppow [email protected] Subject: RE: [Rollei] New Owner? you wrote: >Sorry, but what is the EVS system? Exposure Value System Its a number corresponding to a certain amount of light admitted to the film. The Exposure Value or EV is the same for any combination of f/stop and shutter speed which delives the same amount of light energy to the film. EVS exposure meters give you a single number for the exposure rather than a series of equivalent film speed/f-stop combinations. Its supposed to make things easier. The EV system was introduced on Compur shutters. In order for it to work the shutter speeds must be even multiples of each other and both shutter speeds and f/stops must be on linear scales. The traditional iris mechanism compresses the scale as you go toward smaller stops. EV shutters have a modified iris mechanism which gives even spacing. Rolleis, and some other cameras which use EVS lock the shutter speed and iris settings together so that either can be changed without changing the amount of light admitted to the film. Some Rollei models have a simple way of unlocking the two controls, some do not. I think the Rolleiflex D is the only model where the two adjustments are always held together by a friction clutch. Its a minor inconvenience in an otherwise outstanding camera. BTW, the EVS iris accounts for the five bladed iris found on later Rollei cameras. The peculiar hinging arrangement needed for getting a linear scale is difficult to implement with a large number of diaphragm blades. ---- Richard Knoppow Los Angeles, CA, USA [email protected]

from rollei mailing list: Date: Thu, 22 Aug 2002 From: "Q.G. de Bakker" [email protected] Subject: Re: [Rollei] Using EV on Rolleicord Jerry Lehrer wrote: > The EV scale should only be relative to the film speed. Not even that. EV notation is a shorthand way of indicating all shutterspeed-aperture combinations that give equal exposure. EV 10 (for instance) always is f/2.8 at 1/125 or any other 'equal-exposure' combination, no matter what filmspeed, or level of illumination. What EV is the correct one to use to get correct exposure (given a certain amount of light and using a film having a certain speed) is another matter.

From rollei mailing list: Date: Thu, 22 Aug 2002 From: Richard Knoppow [email protected] Subject: RE: [Rollei] Using EV on Rolleicord ... >Isn't the EV scale relative? I thought that it could >vary from manufacturer to manufacturer. I only use EV >scale to find the difference from shadow to highlight >a little easier. EV scales are constant. Sometimes meters are calibrated in "Light Values" which are abitrary, but the meter calculator will read EV when the LV is set on it. Sometimes Exposure Values are called Light Values, some meters read them directly when some method is available to set the ISO speed for the scale. EV = 3.32log (N2/t) where N = f/stop and t = exposure time. For instance, the meter on the Rolleiflex indicates EV directly. The meter has a place to set ISO-speed. The knobs controlling stop and shutter speed can be locked together for the EV read off the meter. It can then be set for whatever shutter speed or f/stop is desired, the other being automatically set. This system appears to have been originated by Deckel. ---- Richard Knoppow Los Angeles, CA, USA [email protected]

From: Lassi Hippel [email protected] Newsgroups: rec.photo.equipment.medium-format Subject: Re: Help with Apotar/Syncho-Compur Isolette Date: Mon, 11 Aug 2003 Mike Elek wrote: > > The gripe I have with the implementation of the EV system on many cameras is > that it's extremely difficult to alter settings. Most camera makers heavily > sprung the dial. > > So I guess my complaint is with implementation and not necessarily the > concept. I've always liked the concept. You can forget your meter home, if you learn some simple rules. It begins with EV15 ("sunny sixteen"), but there are also other reference points, see e.g. http://www.kenrockwell.com/tech/ev.htm. Implementation is another matter. Having an EV pointer is enough. A time-aperture interlock that cannot be bypassed is a nuisance. -- Lassi
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