Quote Originally Posted by smieglitz View Post
... I have 3 different whole plate cameras, an Eastman #2, a ROC Universal, and a ROC Carleton. I also have at least 4 different-sized plate or film holders in that format!

I've read several posts on APUG and the Large Format Photography Forum about the lack of standardization for this format, both in the past and present day even with new holders coming from Chamonix, Ebony, Lotus, S&S, and AWB. It sounds like a somewhat standard t-distance has evolved taken from the ANSI 8x10 standard of 0.260" but the modern variance runs between 0.260" to 0.300" from what I can glean from forum posts. I just measured an old Eastman plate holder with film sheath and get about 0.300" to the sheath surface.
Tonight I measured the t-distance (depth from the outer bearing surface of the holder to the septum) on the various holders I have. Here's what I came up with:

Eastman Portrait Film Holder #2 for Empire State, ROC Universal, Carleton, and Premo cameras - one side averaged about 0.254" and the other 0.245"... call it 0.250" I guess.
Eastman Plate Holder was just under 0.300"
ROC film holder was ~ 0.310"
ROC plate holder w/film sheath was ~0.280"
older Blair plate holder was ~0.290"
Poco film holder was ~0.300"