Now that you know how much the lens mount is out from the specified 35.00mm +.01/-.03, all that is required is to shim to correct.
You can use any material to shim with as long as you have a broad selection of the right thickness available. I have used negative film base, paper, even aluminum cooking foil for very slight shimming changes. One good source for shims is the hobby shop. I have some etched brass frets of washers made by Athabasca Scale Models that are .008" (.20mm) and .004" (.10mm) thick.
Once you have determined the amount of shim you need, just slip it under the mount base.
Tighten all the screws and re-measure all four corners again. Even if you change just one corner's shim you should measure all four corners.
An Interesting Discussion
I had an interesting discussion recently regarding the correct Lens Flange to Film Plane distance.
The following are excerpts from the thread:
I think the distance you want is 34.85 mm. There is a
table of flange-to-film distances on this website:
Look under buttons for "useful info" and then under
Upon which I asked a noted expert, Henry Scherer, what he
The correct answer is that there isn't any correct answer. The value cited in Peter Tooke's book which is the Zeiss factory specification is an ideal which, in practice, was almost never achieved.
The reason for this is that back in those good old days there was no such thing as any modern method of quality control practiced by anyone in Germany or Russia. In actual practice the actual dimensions of the lens mount as well as the camera body would vary by such a large degree it is my experience that even if one has a camera where the lens flange to film plane measurement is within 35.00mm +0.01/-.03 it is highly unlikely that the rear lens surface will be within the optimal distance from the film plane when it is mounted on the camera.
Zeiss lenses have considerable range of adjustment for the lens cartridge within the lens barrel. And there were a great number of lenses, perhaps most of them, set incorrectly at the factory.
The mounting of the lenses in the rangefinder is also something with a lot of variation. So the rangefinder result has a fair amount of variation in it.
So my overall answer is that it doesn't matter much. There's no point in trying to adjust the position of a lens mount on a camera body when it's likely that the inner machining that sets the position of the lens has a lot of variation.
I think it would have been better for Zeiss to have specified the position of the flanges that are inside the lens mount and to which the lens tabs couple than it was for them to specify the distance from the external tabs. But even if they had done this the variation of everything around the lens mount and which affects the focus is so great this is also rendered relatively meaningless.
There is much truth to be told with this statement. Consider even
that if the Film Plane to Outer Flange distance could be held with
some remarkable tolerance, the Inner Flange is part of a moving
object, the helical itself. Our Jupiter-8 lenses mount to this Inner
Flange. The helical cut groove would have to be cut with unimaginable
precision to position the Inner Flange at a controlled distance from
the film plane. From many measurement I have made it would appear
that the difference in distance between the Outer Flange and the
Inner Flange is 3.00mm. If 35.00mm is chosen as the Outer Flange
to Film Plane distance, then that would make the Inner Flange to
Film Plane distance 32.00mm.
June 24, 2007