PDA

View Full Version : Standard distances for film holders



swmcl
4-Mar-2019, 20:29
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
4-Mar-2019, 20:43
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
4-Mar-2019, 20:59
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
4-Mar-2019, 21:20
The distances for 4x5 vs 5x7 are not the same. 4x5 is 5mm. 5x7 is something like 6.3mm.*


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

pepeguitarra
4-Mar-2019, 21:28
Here you are: http://home.earthlink.net/~eahoo/page8/filmhold.html

scm
4-Mar-2019, 21:29
https://www.largeformatphotography.info/forum/showthread.php?30292-Film-Holder-T-depth-and-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
4-Mar-2019, 21:45
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
4-Mar-2019, 21:56
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
5-Mar-2019, 03:21
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
5-Mar-2019, 05:53
ULF Film holders are made to at least 20X24 inches and may vary T according to matching hulders.

Jim Jones
5-Mar-2019, 08:56
Here you are: http://home.earthlink.net/~eahoo/page8/filmhold.html

No! No! No! Not this damn link again! While the critical depth to septum distance, the "T" distance, is correct, some other dimensions are conspicuously wrong. The "official" source is ANSI/PIMA IT3.108-1998. Google for it, and perhaps you can find a free download. LFPF member animaux has reformatted the information and made it available at https://temp.animaux.de/filmholders.html.
For us who want to dig further, the matter was discussed at length at https://www.largeformatphotography.info/forum/showthread.php?7443-ANSI-Film-Holder-Details.

swmcl
5-Mar-2019, 15:22
Hmmm.

I will reset my conclusions based on Jim's response. Thanks Jim.

Time to double-check.

Bernice Loui
6-Mar-2019, 09:41
4x5 film holder measured on a granite surface plate and height gauge. This is a single example, there WILL be production tolerances that will vary their single measurement example.

inch:
188483

mm:
188484


For ? reason the uploaded image is rotated 90 degrees ???

Bernice

Bernice Loui
6-Mar-2019, 09:43
5x7 film holder measured on a granite surface plate and height gauge. This is a single example, there WILL be production tolerances that will vary their single measurement example.

inch:
188485


mm:
188486



Bernice

Bernice Loui
6-Mar-2019, 09:46
8x10 film holder measured on a granite surface plate and height gauge. This is a single example, there WILL be production tolerances that will vary their single measurement example. This 8x10 film holder would not sit flat on the granite surface plate, so it got a solid carbide cutting tool to aid in flatness.

inch:
188487

mm:
188488



Bernice

Tin Can
6-Mar-2019, 10:07
Exactly! I regret not getting an obsolete granite block from work, but they did give away many straight edges as they were cheaper to buy with certication than to recertify!

I have 3 up to 40" and plenty straight. +/-0.001" by calibrated feeler gauges which need to be replaced often.

I always rotate my iPhone pics in App or PS before posting.

Almost any spec has plus or minus specs, as do holders and many are not flat across the surface.

I also measure film holders and GG distance.

When I first got my S11 Deardorff it was 0.1" off GG spec. More than a few experts here told me, 'that's fine just shoot.'

I had Richard Ritter make five 11X14 holders and match them to his design bail back.

I also checked his work.

Within tolerances, no worries!

Jac@stafford.net
6-Mar-2019, 10:45
I also measure film holders and GG distance.

When I first got my S11 Deardorff it was 0.1" off GG spec. More than a few experts here told me, 'that's fine just shoot.'


Do you measure from the front (lens side) of the glass, or the back side (or subtract the glass thickness or perhaps half the thickness.)

Tin Can
6-Mar-2019, 10:50
No comment


Do you measure from the front (lens side) of the glass, or the back side (or subtract the glass thickness or perhaps half the thickness.)

pepeguitarra
6-Mar-2019, 10:55
... When I first got my S11 Deardorff it was 0.1" off GG spec.

Maybe they left room for the 0.1" thick Fresnel. :)

Nodda Duma
6-Mar-2019, 13:59
I believe the acceptable tolerances are included in the ANSI / ISO standards.

Nodda Duma
9-Mar-2019, 02:56
No! No! No! Not this damn link again! While the critical depth to septum distance, the "T" distance, is correct, some other dimensions are conspicuously wrong. The "official" source is ANSI/PIMA IT3.108-1998. Google for it, and perhaps you can find a free download. LFPF member animaux has reformatted the information and made it available at https://temp.animaux.de/filmholders.html.

That link is awesome and an invaluable resource ... The one issue from a I'm-designing-new-holders perspective is that the critical distance "T" is shown as the distance from the surface of the holder to the surface of the center dividing plate.

I believe "T" should be correctly shown as the distance from the surface of the holder to the image plane. This isn't as important a distinction for sheet film in a sheet film holder, since sheet film thickness is within the tolerance band (marginally). However, for my focus on plate holders it is a critical distinction due to the 1.3mm thickness of my glass substrate.

I may be incorrect, but this is how I interpreted the ANSI standard and I've verified this distinction with antique plate holders. It could be that over time ANSI settled on identifying "T" as the distance to the dividing plate, but that wouldn't make sense from an optical engineering standpoint either as the distance to the image plane (as imaginary as that is) is the critical dimension and would be captured somewhere in the standard... same as for other ANSI / ISO / industry standards showing standardized focus distances.

Jim Jones
9-Mar-2019, 08:46
Yes, it is a problem, especially to critical photographers who have never studied the requirements of film and plate holders. The "H" distance (depth of the film slot) is specified as 0.012". This was necessary to accommodate the 0.010" thick film that I've occasionally used in the past. When 0.004" graphic arts film is used, there is a lot of slop in the slot in which the film rides. The "T" distance to the septum can be defined for all film holders, but defining the actual distance to the emulsion would require a different design of holder. By defining the "T" distance to the septum, not the emulsion, it is up to a critical photographer to load the film with a backing sheet if necessary to bring the emulsion up to the correct position. This is even more important with glass plates. An old ANSI photo plate spec sheet gives the plate thickness as +/- 0.015 for plates up to 8x10, and twice that for larger plates. Here it can be critical that the plate is pressed forward against a surface in the plate holder that is in the image plane. Until universal standards are established to resolve these problems, an understanding by individual photographers can be enhanced by the likes of LFPF member animaux and others who contribute facts, not guesses or links to inaccurate information. This forum seems like the ideal place for the exchange of accurate information unencumbered by the copyright restrictions imposed by ANSI in the past.

Bernice Loui
9-Mar-2019, 09:23
Film flatness and accuracy of film holders and alignment from ground glass to film holder seating area is often not considered. Add to this camera alignment of the front and rear standards. This is why flimsy view cameras do not work for me. The entire system must be precision, accurate and repeatable each and every time the camera is set up then used. Industry standards are OK if all involved follow them and image makers understand and accept this need for standardization and why it is SO important.

This is very much a blending of science-technology-art-creativity. These primary factors needs to be balanced and deeply understood and importance to creative image making appreciated.


Bernice

Nodda Duma
9-Mar-2019, 14:40
This is even more important with glass plates. An old ANSI photo plate spec sheet gives the plate thickness as +/- 0.015 for plates up to 8x10, and twice that for larger plates. Here it can be critical that the plate is pressed forward against a surface in the plate holder that is in the image plane.

I'd be interested in acquiring a copy of the ANSI spec sheet that you reference. What is the #?

In practice I've found that the emulsion of the plate rests within the DOF, as even 120 years ago holder designers understood the same necessity (i.e. the datum being the front of the plate and not the back). So that doesn't bug me so much.

The bigger issue is that new manufacturers of (wet) plate holders are not following any standard for length and width, so for example my 4x5 plates are undersized at 99.5 x 126 +0/-0.5mm from an actual 4" x 5" to accommodate "under cut" holders. That said, I've been in contact with the ISO working group that governs photographic plate dimensions. The current ISO 14548 Rev 1998 "Photography — Dimensions of glass plates" does not accommodate any but a couple of traditional photographic plate dimensions. I think the ISO standard governs plate sizes used for holographic, x-ray, and astronomical observatory applications. So I'm working on submitting an addendum to bring traditional photographic sizes back into the fold. Once incorporated, I can refer any new plate holder manufacturers to that ISO standard. It will follow the same scheme used in ISO 1012 for non standard sheet film sizes (i.e. a tolerance band which scales with the size of the plate) so it's pretty cut and dry.

-Jason

Tin Can
9-Mar-2019, 14:52
Sounds good Jason.

Was that a pun, 'cut and dry'?

Kidding!

Nodda Duma
9-Mar-2019, 15:36
:)

My son would say that it was pungent.