Film holder T distance for banquet holders

[claytume]

Since discovering a light leak in my camera back and not the film holders as I first though, I've decided to check the back further for any other problems. So right now I'm checking film registration and the numbers I have show a large variation between ground glass and film emulsion surface.

So my question is, can someone confirm the T distance for banquet holders. Also I need to know the tolerance, plus or minus. I have the feeling that my setup could be sitting at the outer edges of the tolerance and the ground glass may need shimming.

Incidently I found the numbers for 11x14 holders and tolerance, to me the tolerance seems rather large.

0.332 +/- 0.016

These numbers mean a T distance of 0.316 - 0.348 is ok.

If I remember correctly Sandy King said there are no standards for the banquet sizes.

Clayton

 

[Monophoto]

Clayton -

You might want to read Tillman Crane's article in the latest View Camera.

Tillman had borrowed an antique 5x12 camera several years ago, and after his first trip to Scotland, decided that he wanted to go back with that format to work on a book. In his article, he talks about how he sent the 5x12 holders that he had with the antique camera to Keith Canham to be used to design a new 5x7/5x12 convertible camera. Canham then sent the holder to S&S who used it as a pattern to make some new holders.

The point is that he built his 5x12 system around an antique holder rather than by abstract technical specifications. That implies to me that there aren't suitable specifications for those formats.

 

[Steve Hamley]

So my question is, can someone confirm the T distance for banquet holders. Clayton

Reportedly, there is no standard for film holders above 8x10 for older cameras. Old banquet cameras were not made the same as you have discovered, so the only sure solution is to have film holders made by the same company as your camera or to have someone make holders with the same spacing for you.

Steve

 

[mark]

This thread might help a little

(there was a url link here which no longer exists)

 

[sanking]

This thread might help a little

(there was a url link here which no longer exists)

In ULF size there are ANSI standards only for 11X14" and 14X17". And the T-dimension is actually different for these two sizes, being slightly less for 14X17' (0.320" +/- 0.016) than for 11X14" (0.332" +/- 0.016.

We build all of the S&S ULF holders, with the exception of 10X12", 11X14" and 14X17", with a T-dimension of 0.335", or 8.5mm. This is, allowing for some tolerance, the T-dimension of most older Korona and F&S holders of all ULF sizes.

Sandy

 

[claytume]

We build all of the S&S ULF holders, with the exception of 10X12", 11X14" and 14X17", with a T-dimension of 0.335", or 8.5mm. This is, allowing for some tolerance, the T-dimension of most older Korona and F&S holders of all ULF sizes.

Sandy

Sandy

what is the tolerance for your ULF holders +-?


Clayton

 

[claytume]

Thanks for the replys.

This is a new camera and the camera was built around a new holder so there should be a good match.

The holders are faultless, what I'm struggling to deal with is small assembly faults with the camera. While they're not major, their effect is bad enough to produce light leaks and film registration problems.

Last night I found the source of the registration problem, the clamping system on the spring back wasn't pulling the ground glass frame down squarely. This meant when measuring the bellows side of the ground glass for spacing relative to spacing on the film holder (emulsion face) there was a dramatic variation.

You don't expect to be thrown by these errors with a new camera so I plan to go through everything and get it back to standard specs. While a little frustrating, as I said these assembly errors are not major and not enough to send the camera back.

Clayton

 

[sanking]

Sandy

what is the tolerance for your ULF holders +-?


Clayton

I would allow a tolerance of 0.020" but have never actually measured anything greater than 0.010":, or about .25mm I usually check the T-dimension with a metric ruler, which I find easier to read, and look for 8.5 mm, which is 0.3346457". Since tolerance is about 0.5mm I know that anything below 8mm or above 9mm is out of tolerance.


Sandy

 

[Deckled Edge]

I arrived at perfection the other way around. I bought new S&S film holders for my Korona 7x17, determined the T factor with clamped straight edges, inside calipers, and a micrometer; then shimmed the ground glass to match this dimension. I was obliged to discontinue the use of one old filmholder which was apparently whittled by blind elves. Admittedly this is the more expensive option for those who have collected a Dukes mixture of old holders.
For non-banquet cameras this is not so much a problem, as I use 4 different brands of holders for 11x14, and they are very close dimensionally.

 

[claytume]

I arrived at perfection the other way around. I bought new S&S film holders for my Korona 7x17, determined the T factor with clamped straight edges, inside calipers, and a micrometer; then shimmed the ground glass to match this dimension.

When you see how large the tolerance is for banquet and ULF film holders, perfection is impossible!

I think you'd need to close down the tolerance to that of 4x5 holders which is
+/-0.007 and look at methods to keep the film absolutely flat like the Sinar adhesive holders.

Clayton

 

[sanking]

When you see how large the tolerance is for banquet and ULF film holders, perfection is impossible!

I think you'd need to close down the tolerance to that of 4x5 holders which is
+/-0.007 and look at methods to keep the film absolutely flat like the Sinar adhesive holders.

Clayton

I could claim tolerance of +/- 0.010" with great confidence that all of the current S&S holders meet the standard. But what would be the point? The cameras in which these holders are used have variations in ground glass displacement that are far greater than the tolerance of the holders. Plus, in many cases people are using several different kinds of holders, and they are often mismatched in terms of T-dimension. What I would recommend is to check the T-dimension of every single one of your holders, and then shim the back for the most common measurement.

Another consideration is this. Because of depth of field considerations, which in th ULF world dictate that 1) we use our lenses closed down as much as practical, and 2) must constantly make interpretative decisions as to the best point of focus, I am not sure that decreasing the tolerance of an entire ULF system would make much difference in practical results.

Sandy

 

[claytume]

I could claim tolerance of =/- 0.010 and be almost certain that all of our holders have that. But what would be the point? The cameras that these holders are used in have variations in ground glass displacement that is far greater than the tolerance of the holders. Plus, in many cases people are using several different kinds of holders, and they are often mismatched in terms of T-dimension.

Another consideration is this. Because of depth of field considerations, which in th ULF world dictate that 1) we use our lenses closed down as much as practical, and 2) must constantly make interpretative decisions as to the best point of focus, I am not sure that decreasing the tolerance of an entire ULF system would make much difference in practical results.

Sandy

I agree with what you're saying there Sandy but with new cameras the tolerances can be held much tighter although I'm starting to think it would be better done with an all metal camera.

For my situation I'm enlarging the negs and most of my images are shot at infinity with virtually no foreground. DOF isn't an issue and I'm always trying to shoot the lens as wide open as possible because generally they are windy places I shoot in.

So for what I do it's a big help to close down tolerances as much as possible.

Yes in many other situations wide tolerances are quite workable and contact printing helps too.

Clayton

 

[Deckled Edge]

When you see how large the tolerance is for banquet and ULF film holders, perfection is impossible!
Clayton

Perfection is possible. It's just not cheap. If perfection is defined as tack sharp negatives edge to edge and corner to corner, I can get that with every holder I use on the Korona. If perfection is a concept involving laser measurement to 10^-23Å, then I stand corrected. True, you can't control infinite variables in the field. True, old cameras are cranky. True, several old film holders won't match dimensionally. True, I have VERY sharp 7x17 negatives, and I paid through the nose to achieve this. To paraphrase the old joke, Sharp; wide open; short exposure. Choose two.