focus plane tolerance

archer · May 11, 2010

I just installed a new ground glass in my camera back and measured the distance from the glass to the back flange and then inserted a film holder with a piece of film in the holder and measured the same distance with a digital depth guage. What is an acceptable discrepancy between the two? I realize it should be very small or better yet the same but what is an acceptable variation.
Denise Libby

ic-racer · May 11, 2010

What you can get away with will depend on format. For 6x9cm filmholders if its a fraction of a millimeter off it will likely give trouble. On an 11x14 in camera I suspect it could be off a half millimeter and still be OK.

Sal Santamaura · May 11, 2010

archer said:
...what is an acceptable variation...

See the second paragraph of this post:

http://www.largeformatphotography.info/forum/showpost.php?p=288830&postcount=2

ic-racer · May 11, 2010

Sal, thanks for the link. So tolerance of 0.016 inches is about half a millimeter, just what I would have expected.

archer · May 12, 2010

Thank you both for your answers. I find that I'm averaging 0.003 and that should be close enough for 4X5.
Denise Libby

focus plane tolerance

archer

ic-racer

Sal Santamaura

ic-racer

archer

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