12X20 Film Holder Modification

[OKAROB]

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.

[RichardRitter]

Back in the early 1900's late 1800's some camera were made with the ground glass in back wards.
I have run into this quite a few times over the years.

[diversey]

I could not find a correct film holder when I got my Folmer-Schwing 12x20 camera, I contacted and asked Firestudio to make a couple of film holders according to the camera back measurements.

[Greg]

Of all the formats, I have found the greatest variance to be with the whole plate format and the least with the 8x10 format. Years ago I purchased some 14x17 wooden holders that amazingly had no ribs. A local furniture maker cut up some ironwood ribs for me, and I glued them in place with a minimal amount of very carefully applied Gorilla glue and clamped them overnight. Used the holders for many years and the ribs never came loose.

[Len Middleton]

Back in the early 1900's late 1800's some camera were made with the ground glass in back wards.
I have run into this quite a few times over the years.

As you found on my 8x20 Korona Panoramic View.

And thank you for that. Not certain how much expensive film being out of focus would I have gone through trying to chase that problem…

[OKAROB]

Richard, that makes sense. I could not imagine a film holder with such a shallow T depth. Thanks!

Thanks to everyone on this forum that made me aware of the differences in film holders and also T depth. I knew buying that holder I was going to have to make adjustments. Same issue with older 11x14 holders. I appreciate everyone’s advice on this forum!