Standard distances for film holders

[swmcl]

Hi,

I'm using Fidelity film holders for 4x5 and 5x7 and I am a little worried that my focussing distances are out a little. Is there a defined standard for the distance from top face of film holder to film surface ? Is the distance the same for 4x5 as 5x7 ?

And where do you go to get this measured and skimmed ?? (what kind of workshop or business does this...)

Cheers,
Steve

[pepeguitarra]

Yes, there are standard distances for each plate. There is an ISO standard that I was going to purchase one day last year, when I intended to build some dry and wet plate holders. I finally set with Chamonix 4x5. All the other antique holders I bought at the bidding place were no good at all. They were built before the standard. I know you want to know standards for film holders, that is the same. I don't recall the standard. Jason Lane, the dry plate maker, knows the number of the std., you can purchase it in the Internet. But he may want to share with you the dimensions. Search his name in this forum.
-------------------
Update: The International Standards Organization - ISO - standard sheet film sizes, which have been voluntarily adopted by most of the world's manufacturers of sheet film. The governing standard, ISO 1012, describes sheet film dimensions. (Copied from Jason Lane's website)

[Mike in NY]

Steve, some additional information might help:

• We're assuming the image appears focused on the gg, so is it the film or your prints that appear out of focus, or both?
• How far do you typically stop down after focusing? (Let's rule out diffraction by stopping down further than needed.)
• Does it occur with all of your film holders, regardless of size and make, or only some of them? (If this is occurring across multiple film holders, I'd be more inclined to consider adjusting the camera before adjusting multiple film holders.)
• Does it occur on multiple cameras, or by chance are you using a single camera such as a 5x7 with a 4x5 reducing back?
• If it's occurring with just a single camera, has the back been modified in any way to your knowledge?
• Does this occur with different lenses?

[Nodda Duma]

The distances for 4x5 vs 5x7 are not the same. 4x5 is 5mm. 5x7 is something like 6.3mm.*


*I’m working off memory. As pepe mentioned, there is an ISO standard that defines the distances.

[pepeguitarra]

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

[scm]

https://www.largeformatphotography.i...-ANSI-Standard

Z38.1.51-1951 is the American Standard Dimensions for photographic double film holders of the lock-rib type. "T" specs are as follows along with the tolerance for error. For 2-1/4 by 3-1/4, 3-1/4 by 4-1/4 and 4 by 5 holders the depth is 0.197" and the tolerance is +/- 0.007". For 5x7, depth is 0.228" and the tolerance is +/- 0.010". For 8x10, depth is 0.260" and the tolerance is +/- 0.016".

[swmcl]

Yep.
Thanks guys.
The answer is 0.197" and 0.228" or 5.00mm and 5.79mm.
Now I need to make sure the camera (a Shen Hao) is set at those settings.

Further question ... these measurements are without film in the holders right ? And according to me and the Ilford datasheet, sheet film is 0.18mm thick. I have measured my film to be what Ilford says it is ...

I should mention that if you do buy a Shen Hao that you will be required to do many adjustments to it just to get it tuned.

Cheers,
Steve

[swmcl]

So.

My 4x5 ground glass holder should have a distance of 5.00 - 0.18 = 4.82 mm from its touching surface to the glass.

My 5x7 ground glass holder should have a distance of 5.79 - 0.18 = 5.61 mm from its touching surface to the glass.

OK?

[Nodda Duma]

The distances are to the focus plane, so measure to the surface of a loaded sheet of film (or plate). Don’t assume a thickness of the film if you are tracking down a focus issue with your camera.

So it’s 5 and 5.79mm respectively to the ground glass, period.

[Tin Can]

ULF Film holders are made to at least 20X24 inches and may vary T according to matching hulders.