I recently purchased on Ebay a new 12X20 film holder. I must say that it is nicely made and at a fair price for a new holder.....but it doesn't conform to my Korona 12X20 camera back. The seller did include a diagram of the holder dimensions, so I knew when I purchased the holder I would have to make some modifications both to the holder and my camera back. Thank goodness when I purchased my camera it came with parts for an extra back. Interestingly the T dimensions on the extra back were different by .070" so I was going to have to shim it anyway. The new film holder is +.040" from my Korona film holders also the width of the holder is -.250" . I have cut two 1/8" (.125") thick strips of red oak from a plank that are 3/4" wide and glued them to each side of the film holder. So now the film holder fits the camera back.
I will need to adjust the T depth of my second back by adding 3/16" (.180") thick X 1/4" (.250) wide strips and used them as shims for the ground glass to achieve a T distance that matches my new holder. Yes, I know that seems awfully thick but oddly the second camera back had a really shallow T depth. Maybe the prior owner modified the camera backs T depth for some reason. I will post photos of the camera back when I am finished. There is no way to adjust the film holder's T depth without risk of damaging the film holder.
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