Bausch and Lomb Telephoto Adapter (1900s)
Photo thanks to Milan Zahorcak
[email protected]
Related Local Links:
Diopter Lenses Page
Large Format Lenses
Telephoto Lenses
The photo notes below from the original owner's posting on an EBAY ad
(used with permission along with photo above) makes more sense after you
visit my Diopter Lenses Pages. As part of that
page, I reference several articles and provide formulas for how various
diopter lenses can be used to change the focal length of the lens,
depending on how and where they are used.
For example, most of us are
familiar with the use of moderate negative diopter lenses in
teleconverters to produce a telephoto adapter effect when used at the
rear of a conventional lens. These principles have long been known,
although now mostly forgotten, as ways to stretch or compress your lens
focal lengths. These tricks are especially handy in large format and
medium format fixed or prime lenses, where we rarely encounter zoom
lenses for many reasons. By use of the appropriate diopter lenses, you
can shift the effective lens focal length up or down a modest degree
without seriously compromising image quality (a little loss is inevitable).
See the Bausch and Lomb Protar Zoom lens for Graflex(?) view cameras covering 300mm to 600mm.
B and L Telephoto Attachment, c1900. This tele attachment was designed to accept an existing lens - preferably a short focus portrait lens, but any lens that fit would do - and significantly increase the focal length. For illustration, the attachment is also shown with a Darlot portrait lens attached. When the adapter was purchased, an adapter that fit the lens to the attachment would also be obtained. The threaded adapter is still attached and can be seen in the photo, but finding a lens to fit could be tricky. I know it also fits a large, coarse thread B and L iris shutter that I own.
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