film holder depth- ANSI spec?

[Mark Sampson]

That's the information I'm looking for. I couldn't find a link to the data elsewhere on this page; for once I need numbers and not anecdotal evidence. So I'll put the question up for the experts....

[robc]

read this:

http://www.largeformatphotography.info/holders.html

then register the fact that not all filmholders conform to the standard. That makes a mockery of the standard. It also means, as I have repeatedly stated before, that the most important thing is that YOUR GG IS THE SAME DEPTH AS YOUR FILM HOLDERS WITH FILM IN THEM. If you get that right the standard is irrelevant( like most standards).

[Michael S. Briggs]

Edward Hoover has posted the ANSI specifications at http://home.earthlink.net/~eahoo/page8/filmhold.html. The depth to the septum for 4x5 holders is 0.197 +/- 0.007 inches (5.0 mm), that of 8x10 holders 0.260 +/- 0.016 inches, etc. A correction is that the row labeled "Depth to film surface" should be "depth to septum". The ground glass on a camera should be a closer to allow for the thickness of the film, about 0.190 inches on a 4x5 camera.

I have measured the depth of many of my modern 4x5 holders and found all that I measured to have depths well within the tolerance. Obviously there are bad holders out there, so there are no guarantee that all of yours meet the standard.

[Mark Sampson]

Thank you, Michael. That's exactly what I was looking for.

[Malcolm Stewart]

Just to add a little to this thread.

Measuring these depths, and being confident in one's results, is not trivial. I've tried using a variety of methods including digital verniers, parallels and depth micrometers etc. - all checked against appropriate gauges. I started out checking my old wooden MPP filmholders, and to my surprise these are remarkably parallel - even though they are to an older and different standard. Some of the more modern plastic film holders appear to have a slight tilt across their width, albeit within the specification limits.