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Old October 16th 11, 06:48 PM posted to rec.photo.equipment.large-format
Richard Knoppow
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Posts: 751
Default Oddity with Protar VII


"Cheesehead" wrote in message
...
I was looking @ the rear cell on my B&L lens, and it's 23
1/4" f/l.
The front cell is 18 7/8" f/l.
The old B&L table never put a longer cell in the rear.
http://www.cameraeccentric.com/html/...schlomb_3.html
I got the camera from the original family owner, and it
was apparently
ordered this way in 1923.
Makes me wonder ... any thoughts on this anomaly?

Either cell will fit on either end, somone just reversed
them from normal. The correction is slightly better when the
longer lens is in front. When the single cells are used
alone they perform best behind the diaphragm but there is
really little difference in correction. Since the principle
points of the single cells are displaced in the direction of
the curvature the distance from the focal plane is less when
the lenses are mounted on the front of the shutter. This
allows some lenses to be used on bellows which are not long
enough to focus them when on the back of the shutter. The
difference is significantly more than just the mechanical
length although that also counts.
Both cells should have the same threads and both sides
of the shutter should be the same.
Both B&L and Zeiss sold Protars in sets with up to four
cells of different focal lengths which could be combined or
used alone. The most elaborate B&L set also came with an
extra-wide-angle Protar.


--
Richard Knoppow
Los Angeles, CA, USA