5x7 T-distance

[jodyake]

I am in the middle of making a 5x7 Plate holder and I need someone to confirm that the T-distance for a 5x7 is 0.228. I have seen a few other measurements but this seems to be the US standard. Thoughts?
http://incameraindustries.com/

[Daniel Stone]

This website claims it to be .228 as well

http://home.earthlink.net/~eahoo/page8/filmhold.html

Dan

[Jim Jones]

The T-distance is indeed .228" +/- .010" according to the 1951 ASA standard. Keep in mind this is the distance to the back of the film slot, not to the emulsion. The slot is .012". This leaves a sloppy tolerance for the actual position of the film. A film or plate holder loaded from the back instead of from the front can minimize this slop.

[jodyake]

so if the holder loads form the back should the t distance be .216?

[Jim Jones]

Yes, or a wee bit more. While the slot is .012", film varies from maybe .004" to .010" with (I believe) .007" being common.

[jodyake]

thanks Jim!

[EH21]

Stupid follow up question then the focus screen should be set such that the imaging surface is at the same point correct? If there is a fresnel in front of the screen, one would still want to set the matte surface of the screen to that dimension.