The ANSI information for standard film holders is easy enough to access, and shows 5.00mm as the depth from a 4x5 film holder's surface to the film plane.

Not as easy to find, however, is this specification for old slotted 'graflex' type holders. Does anyone know where this information might exist? The patents for the holders and magazines contain no measurements. I'm primarily seeking the depth from surface to film for 4x5 holders, but am also interested in 3.25x4.25 and even possibly 5x7. I have a ground glass panel for 4x5 graflex backs around, but the measurements vary wildly in it, probably due to it being made of wood and 80 years old. Measuring at each of the four corners, I have: 5.68, 5.75, 5.82, 5.75mm.

I'd love to know what the correct depth should be for this, if anyone knows it. This GG panel just doesn't seem to be a great example to work from.

My vintage Bag Magazine measures 6mm to the film surface.

The Graflex holders are deeper than standard 4x5 holders. I measured all 4 corners of both sides of two of my Graflex holders, and the following are the results as average and range: 0.226" +/- 0.002" ; 0.224" +/- 0.002" ; 0.221" +/- 0.002" ; 0.224" +/- 0.002" . The overall average and range for these four sides is 0.224" +/- 0.005", or 5.69 mm. This is a remarkable degree of precision for wooden film holders (I've never seen plastic Graflex holders - were they ever made?). These measurements were made with film in place - to the film plane, in other words - using a depth gauge which spanned the corner. (Film thickness 0.008").

By comparison, the ANSI standard for 4x5 holders is 0.197" +/- 0.007". The Graflex holders are therefore deeper by about 0.027" - nearly 1/32". If you want to use a regular 4x5 ground glass back to check focussing on a Graflex, you will therefore have to shim it by this difference.