Quote Originally Posted by Steve Smith View Post
Why won't they be the same for the same focal length?


Steve.
Yes and No, in theory.

The issues are that Focal lenghts are nominal so a 210 lens might really be 207mm, another type 213mm, for high accuracy the scales would be positioned slightly differently, the scale itself is the same. In practice the difference is negligible and well with the 30% +/- tolerance that's acceptable for shutter speed accracy, OK we are talking apertures but well below 1/3 of a stop.

I've been using similar lens cells (to the OP) in various shutters but I have the advantage of being able to compare the scales on the shutters with those on other lenses and/or knowing what lenses were in them originally.

So for instance I'm using a pair of 150mm f6.3 Geronar cells in an Agi #0 shutter off a 6x6 Agifold camera which originally had a 75mm lens fitted and in thiscase I simply use double the marked aperture. What confuses issues are that sometimes the lens barrel itself restricts the maximum aperture, a a 90mm f6.8 Angulon in a Compur #0 uses only part of the aperture range.

Ian