ANSI Film Holder Details

[Jim Jones]

Pere: Please do NOT rely on the link you cited in post 10. It contains misleading and erroneous information. Most important, the critical depth to film surface is actually the distance from the film holder to the septum. The distance to the emulsion can be as much as 0.012 inches or 0.3mm less. This error can cause a noticeable loss in sharpness when using fast lenses. The exposure height figures are obviously wrong. The figures do not include tolerances, which should be important to anyone relying on them to produce film holders.

[Pere Casals]

Pere: Please do NOT rely on the link you cited in post 10. It contains misleading and erroneous information. Most important, the critical depth to film surface is actually the distance from the film holder to the septum. The distance to the emulsion can be as much as 0.012 inches or 0.3mm less. This error can cause a noticeable loss in sharpness when using fast lenses. The exposure height figures are obviously wrong. The figures do not include tolerances, which should be important to anyone relying on them to produce film holders.

Jim, I guess you are speaking about post 9.

both links have the same information:

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

https://temp.animaux.de/filmholders.html

the depth to film surface is the dimension that has a tolerance: +/- 0.1778mm

So for 4x5 the "Depth to film surface" isn't 5.0038 +/- 0.1778mm ???

What's the right depth ???

This is the single dimension that I'm concerned !

I was planing to make a film to GG focus alignment test, but i'd like to know the right depth for 45, 810 and 1114


PD: Thanks Jim, I found it, here there is the information:

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

Here it explais the septum vs film discrepance:

http://www.largeformatphotography.in...epth-ANSI-spec

[RichardRitter]

The values for the T measurement shown in post 9 are correct

The label is wrong it should be "depth to septum" In the ANSI listing it is refereed to as the "T" measurement.

[Jim Jones]

The ANSI/PIMA IT3.108-1998 I downloaded from ANSI years ago agrees with Richard Ritter and includes the metric T distance of 5 +/- 0.178 mm for holders 2x3 to 4x5. For 5x7 it is 5.79 +/- 0.254mm. For 8x10 it is 6.60 +/- 0.406 mm. For 11x14 it is 8.43 +/- 0.406 mm. For 14x17 it is 8.13 +/- 0.406 mm. Some sources give slightly different dimensions, apparently from converting between metric and inches. Someone could do this site a great service by verifying, consolidating, and publishing correct information on film holder dimensions in an appropriate place.

[animaux]

I’m happy to doublecheck all the values and update my table if you are OK to share the ANSI file.

[williaty]

I'd like a look at the ANSI standard as well. I went to ANSI's website to buy the damned thing and eliminate the confusion only to find they no longer have a listing for "ANSI/PIMA IT3.108-1998 American national standard for photography (cameras) : double film holders (lock-rib type)-- dimensions". The closest-sounding thing they have a listing for is "MIL-H-3526C NOT 1 Holder, Photographic Sheet Film, Double, Lock Rib". For $25, I'd like to know that's an equivalent document before I spend the money.

[williaty]

Found a breadcrumb. The standard we're looking for had a proposed status change to Withdrawn in January of 2003. This was under the care of something called the International Imaging Industry Association (I3A). The I3A was a merger of Photographic and Imaging Manufacturers Association (PIMA) and the Digital Imaging Group in 2001 but I3A was disbanded in 2013. So it looks like IT3.108-1998 isn't a standard ANSI provides (or even keeps track of) anymore and even the group responsible to killing it has died.

If anyone actually has a copy of IT3.108-1998, I'd very much appreciate being given a copy since it can no longer be obtained through ANSI.

[animaux]

Thanks for the insight!

If anyone actually has a copy of IT3.108-1998, I'd very much appreciate being given a copy since it can no longer be obtained through ANSI.

Me too!

[Pere Casals]

IMHO this post solves the thing: http://www.largeformatphotography.in...post164959IMHO.

As the "Depth to film surface" here http://home.earthlink.net/~eahoo/page8/filmhold.html

is in reality "the depth to the septum" then the manufacturing of the holder is well determined.


The distance from GG to the film surface is in fact a parameter of the camera back, not of the holder.

In fact the holder cannot have the "Depth to film surface" technically specified because it will vary depending on the thickness of the film we use !!!!

With glass plate holders this was not an issue, because a flange is ensuring the position of the emulsion surface.

In the case of film, the reference surface ensures the position on the back of the film, so the emulsion position has an slight variability depending on the film thickness, that I guess is of little relevance in practical conditions. But confusion comes from that...

(this is IMHO)

[animaux]

I’d think the variance in the thickness of the film should be well within the tolerances. I have no data though.

Still I’d love to see the original ANSI spec, especially to see if there are more details.