[LargeFormat] 8x20 to 12x20

[Craig Koshyk]

Hi All,


I am currently restoring an 8x20 banquet camera. I have taken it apart 
(photographing each step of the way so I know how to put it back 
together!) and have stripped the finish from the wood. A friend of 
mine, an excellent woodworker is doing some minor repairs to certain 
areas. His work has been so good that I have asked him to actually 
replicate each piece of the camera in mahogany. I have another friend 
who is a metal smith. He has agreed to replicate the brass parts (I 
will purchase bellows and gears etc. on line).

When all is said and done I will have sufficient parts/pieces to make 
two cameras, the refinished original as well as a brand new one. 
However the thought occured to me that I can simply scale the back of 
the replica camera up to 12x20 from 8x20.

My question is this:

How do I caluclate the amount of extra width I need on the back. The 
image size of the 8x20 is not exactly 8x20 (something like 7 5/8 x20) 
and the slot for the film holder obviously has its own measurements to 
accept an 8x20 holder. It seems to me that I really need an extra 4 
inches of width, n'est-ce pas? Or is it a bit more complicated than 
that?

Would anyone on the list be so kind as to measure their 12x20 back for 
me so I may make one like it for my camera? I would need all the 
appropriate measurements including inside and outside dimensions, film 
holder size etc. I can then compare them to the 8x20 back to see where 
I need to add the extra room.

Thanks,

Craig K.