Building a film holder...

[barryjyoung]

Hi Jim:

I think maybe some people measure the T distance with the holder empty and some measure it with a sheet of film in place. I just measured a piece of 4x5 transparency film and it was .007 thick. Make sure when you are mounting groundglass that you make the front surface of the groundglass at the same depth as the actual surface of the film not the holder septum.

As far as 7x17 holders, I have info on T dimension from lotus, and a Korona holder and a no name holder I have measured and they are .3563 to .3570 which is very little variation. The S&S is the only holders I know of that have a T distance of .3346. Even with .007 for film, the T distance would only be .3416. I do not understand how the dimension can be so different for S&S holders. I do know that those guys know what they are doing though. Sandy King (S&S Holders) on photo.net says Wisner holders are .332 T dimension.

Perhaps there are 2 different standards based on T dimension?

Here is one of the big problems with ULF film holders.

I have a page from the Canham website that lists dimensions for several ULF formats. They list a T-dimension of .357 (8.9mm) for 7x17, 8x20 and 12x20. That is a difference of .023 from the S&S holders. That seems to me to be a huge difference. If I have 7x17 Canham camera designed for .357 would I get unsharp negatives with a S&S film holder? Or vice a versa using a holder built to Canham's specs in a non-canham camera?

What is the standard? Or do we simply pray that the holder and GG will be in agreement enough to get apparently sharp results? Or when someone builds a camera should they split the difference and go with .345 for the T-dimension.

I bring this up because I have seen the Canham dimensions brought up many times on APUG and the LF photography forum as the measurements to be followed. I also am aware that there is a +/- tolerance with every format. Maybe .023 fits that range. Seems like an awful lot though.

 

[barryjyoung]

Hello Geert:

I am using the same .050 inch black paper based phenolic I am using for darkslides. I have altered the design slightly to accomodate the thinner septum, the holder I started with had .062 thick septum.

Barry,

I had overlooked your post. I looks like a nice start on the holders.

What kind of septum are you planning to use? I have aluminium sheet in 0.5mm thickness, the septum groove in my (homemade & prototype) holders is only 1mm.
T-dimension is 8.8mm.

Greetings,
Geert

 

[Jim Chinn]

So Barry,

Which T-dimensions are you going to use, or are you still researching?

 

[barryjyoung]

Hi Jim:

Thanks for asking. I am going to use the Young Camera Company Standard OU812 which is .3566 (smack dab in the middle) for Korona/Canham style holders and .3320 for Wisner/S&S type holders. This should make me compatible with everyone. And unlike the ANSI standard, instead of +/- .016 on T dimension which means there could be as much as .032 (1/32nd inch) difference between a high and low in tolerance dimension, I will hold this dimension to +/-.0025 and shoot for .0010. The other dimensions don't need to be so tight. I do not have other dimensions for any features of the Wisner/S&S holders except T dimension yet, but I will have. I have a suspicion that the dimension is the biggest difference, but do not know that for sure.

So Barry,

Which T-dimensions are you going to use, or are you still researching?

 

[barryjyoung]

That should have said "I have a suspicion that the T dimension is the biggest difference, but do not know that for sure."

 

[Colin Graham]

Hi Barry-
You're up early! I wanted to ask, are you putting a secondary light baffle of some sort in the darkslide groove? Those slots looked wide to me (if I'm seeing it right). Also, is that mahogany you're using? Looks great, by the way. Thanks, Colin

 

[barryjyoung]

Hi Colin:

I work nights at my real job which is one reason I want to make cameras and holders for a living.

A secondary baffle? No. Just a darkslide that fits the grooves, They will be light tight. There is a .572 minimum light path at 180 degrees. No way that is going to leak. I can send you a drawing if you have a CAD program.

I use cherry since it is not an endangered wood and is domestically grown. I will not use any rain forest wood.

Hi Barry-
You're up early! I wanted to ask, are you putting a secondary light baffle of some sort in the darkslide groove? Those slots looked wide to me (if I'm seeing it right). Also, is that mahogany you're using? Looks great, by the way. Thanks, Colin

 

[barryjyoung]

I just spent the last 40 minutes writing up my procedure for grinding standard 10 inch saw blades down to .050 inch width of cut for making the grooves in film holder parts and when I tried to submit it, I got dumped to a 404 error message so I am not going to risk another 40 minutes doing it again. Sorry.

 

[Jim Fitzgerald]

I just spent the last 40 minutes writing up my procedure for grinding standard 10 inch saw blades down to .050 inch width of cut for making the grooves in film holder parts and when I tried to submit it, I got dumped to a 404 error message so I am not going to risk another 40 minutes doing it again. Sorry.

Barry, I know how frustrating that is! I applaud your dedication. I for one would like to see the procedure! I've been trying to post some photos and I keep getting an error code! What you've done takes a lot more thought.

Jim

 

[sanking]

Hi Jim:


As far as 7x17 holders, I have info on T dimension from lotus, and a Korona holder and a no name holder I have measured and they are .3563 to .3570 which is very little variation. The S&S is the only holders I know of that have a T distance of .3346. Even with .007 for film, the T distance would only be .3416. I do not understand how the dimension can be so different for S&S holders. I do know that those guys know what they are doing though. Sandy King (S&S Holders) on photo.net says Wisner holders are .332 T dimension.

Perhaps there are 2 different standards based on T dimension?

Barry,

First, I am not sure that Wisner is making holders any more. Perhpas he is, but I have not seen any new ones on the market in a long time and the folks who deal with him a lot contact me often about holders.

Considering the depth of field that is typical of lenses we use with ULF cameras a difference between a Wisner T-dimension of 0.332' and Lotus at 0.357' is not something you would ever notice in practice, in my opinion as a user of ULF cameras in sizes up to 20X24". Korona holders measure all over the book, from 0.330" to 0.370", or even more, so don't even consider using that as the standard. In any event, while it is good to focus on precision, T-dimension is not nearly as important a consideration in ULF work as it would be with 35mm or even 4X5. If you shoot for a T-dimension of around 0.350" and can stay within tolerance of =/- 0.015 your holders should perform to all expectations in practice.

As for the S&S holders, all of our holders have a T-dimension of 9.0 mm or 0.354", to tolerance of at least +/- .0.010", except the 14X17" which is to ANSI standard of 0.335". That assumes measurements are taken at room temperature of about 70F and RH of around 50%. American cherry, which we use in most of our holders, is very stable, but will expand and shrink in conditions of low and high humidity. Walnut is also very stable, but sligthly less so than cherry. We believe cherry is the slightlyh better choice for holders, but walnut has a more exotic look and some customers prefer it. Practically speaking, I don't think there is much differnce, and all of the holders I use in my own work are of cherry. .

Hope this information is interesting and perhaps useful to you.

Sandy King

 

[barryjyoung]

Hi Sandy:

Yes, that is very helpful, thank you.

So, how have you at S&S solved this problem of widely varying dimensions? Do you have a zillion model numbers all of different dimensions? Do you alter existing holders by gluing on shim or cutting away material? This has been bothering me since I started researching this project. Do you make them to fit customers cameras?

+/- .015 inch on T dimension? Wow, that is a mile. I was under the impression that the limited depth of focus provided by the long lenses used on ULF cameras made the T dimension more critical rather than less. I can easily hold +/-.0025 when manufacturing holder parts, of course humidity and to a lesser degree temperature will take the punch out of all that hard won precision.

Humidity is another thing that has been causing me emotional distress. I have never used a camera larger than 8x10 so I do not know how much of a factor humidity really is. When you are using a giant camera do you allow in some way for changes caused by humidity? I would think that the difference between summer and winter would be particularly troublesome.

I have Walnut on the shelf too. Cherry is the wood I will make holders from. I like working in walnut, but Cherry is not as abrasive on my tools or on my lungs.

I want to thank you for the information. Very gracious of you.

Barry,

First, I am not sure that Wisner is making holders any more. Perhpas he is, but I have not seen any new ones on the market in a long time and the folks who deal with him a lot contact me often about holders.

Considering the depth of field that is typical of lenses we use with ULF cameras a difference between a Wisner T-dimension of 0.332' and Lotus at 0.357' is not something you would ever notice in practice, in my opinion as a user of ULF cameras in sizes up to 20X24". Korona holders measure all over the book, from 0.330" to 0.370", or even more, so don't even consider using that as the standard. In any event, while it is good to focus on precision, T-dimension is not nearly as important a consideration in ULF work as it would be with 35mm or even 4X5. If you shoot for a T-dimension of around 0.350" and can stay within tolerance of =/- 0.015 your holders should perform to all expectations in practice.

As for the S&S holders, all of our holders have a T-dimension of 9.0 mm or 0.354", =/- .0.10", except the 14X17" which is to ANSI standard of 0.335". that assumes measurements are taken at room temperature of about 70F and RH of around 50%. American cherry, which we use in most of our holders, is very stable, but will expand and shrink in conditions of low and high humidity. Same is true of walnut, even more so. We believe cherry is the bette wood for holders, but walnut has a more exotic look and some customers prefer it. Practically speaking, I don't think there is much differnce, and use cherry for my own work.

Hope this information is interesting and perhaps useful to you.

Sandy King

 

[sanking]

Hi Sandy:

Yes, that is very helpful, thank you.

So, how have you at S&S solved this problem of widely varying dimensions? Do you have a zillion model numbers all of different dimensions? Do you alter existing holders by gluing on shim or cutting away material? This has been bothering me since I started researching this project. Do you make them to fit customers cameras?

There is no way in the world you will be able to reconcile manufacturing to all of the different back sizes out there in the ULF world. We have tried to do this in some cases to satisfy specific needs but in the end I would recommend that you establish one size and stick to it. If you make holders in one format in two or three different sizes to satisfy specific customer needs this might come back to haunt you one day with a customer who for some reason acquires two of your holders with different dimensions and one will not fit his camera. Believe me, we have done this and it has caused us some headaches.

The issue of what tolerance is acceptable on T-dimension has to be understood within the context of circle of confusion, depth of focus, and depth of field for the lens and format. If you were to measure the T-dimension of a bunch of old Korona and F&S holders I would not be at all surprised to find a gross differnce in T-dimension of over 0.030", yet because of the issues of DOF and DOF it is not likely IMO that you would ever detect the difference in actual use, unless of course you decided to use one of your long focal length lenses at close distance with the aperture wide open. If you can hold tolerance to 0.010" or less T-dimension is a non-issue with ULF, and I say that from the prespective of user more than as maker.

Humidity is a major issue. You need to leave plenty of room for your septum, and plenty of room for the dark slides because both phenolic plastic and aluminium will also expand and contract with temperature. And sometimes these materials work against each other, say in very arid and hot climates.

Sandy

 

[barryjyoung]

Wow! Thank You Sandy King!

You have shed some light on potential problems that only another film holder manufacturer would really know about. I am very suprised and appreciative of your willingness to share information that might save me some big headaches in the future. Please let me know if there is anything I can do for you in future. I wish more business people were as open and friendly as you are and hope that I can learn from your example.

What do you do about customers backs which are not a good fit for your holders? This must be the most troublesome aspect of film holder manufacturing. Do you have a stack of letters from customers saying that their pictures are all out of focus? I understand about making one size and sticking with it, but it seems to me that that will not please all of the people all of the time. Do you advise them to modify their backs to fit available holders? That probably would make the most sense and in the long run would be less expensive by far than having all the film holders custom made.

Thank you again.

 

[sanking]

Wow! Thank You Sandy King!

You have shed some light on potential problems that only another film holder manufacturer would really know about. I am very suprised and appreciative of your willingness to share information that might save me some big headaches in the future. Please let me know if there is anything I can do for you in future. I wish more business people were as open and friendly as you are and hope that I can learn from your example.

What do you do about customers backs which are not a good fit for your holders? This must be the most troublesome aspect of film holder manufacturing. Do you have a stack of letters from customers saying that their pictures are all out of focus? I understand about making one size and sticking with it, but it seems to me that that will not please all of the people all of the time. Do you advise them to modify their backs to fit available holders? That probably would make the most sense and in the long run would be less expensive by far than having all the film holders custom made.

Thank you again.

Barry,

First, as I suggested you should not worry too much about T-dimension. If you can keep the T-dimension to tolerance of +/- 0.010", which is very easy to do, your holders will satisfy every practical requirment. That is because of depth of focus, which is a range of focusing movement over which it is not possible for the eye to see any difference between sharp and blurry. This depends on the diameter of the circle of confusion, on the lens aperture, and on the distance between the lens and the subject. Depth of Focus (DOF) increases with the COF and subject magnification, but decreases with wider lens aperture. It is least at close distances and greatest at infinity.

There is a good discussion of DOF in Ralph Lambrecht's Way Beyond Monochrome, and a couple of formulas. Since DOF is least at infinity, that is the critical one on my opinion. It is d= 2 X COF X N, where COF is the circle of confusion and N is the aperture of the lens. Assuming a critical observation and a COF of .085 that would result in resolution of 12 lppm on the film, the DOF at f/9 would be about 1.5 mm, which amounts to 0.06". And this figure would be much greater if you used the lens at a smaller aperture, as would be expected, and if you used a standard observation COF of .252, and/or if you used the lens at greater magnification for close-up work, which also increases DOF. Of course, these figures are based on contact printing and would change if the negative were enlarged but even a magnificaton of 2X-4X would not require tolerance greater than about 0.015" to get resolution of 12 lppm on the negative. However, bear in mind that the overwhelming majority of ULF negatives are exposed at much smaller apertures than f/9, which further increases DOF.

In short, don't obsess about the T-dimension. If you keep it at about 0.350" with a tolerance of les than +/- 0.010 you should never have a complaint about T-dimension, and certainly not from anyone with a real understanding about sharpness.

The main thing is that the holder fits smoothly into the camera back, and that the rib-lock engages the groove in the camera back. But, bear in mind that the width and location of the groove on Lotus backs, and the Wisner backs I have seen is different. I have a customer now who has a 12X20 Wisner, and the width of the back is about 12.6", in contrast to the width of a Canham back which is about 13". Lotus is different, slightly less than 13" though I don't have the exact figure. In general if someone has a back that is too narrow to accept the S&S holder it is possible to sand material off the holder to fit the back, and while this is not complicated, we do not generally provide this service.

The position of the rib-lock is usually easier to resolve. If you look at ten Korona holders the rib-lock is likely to be in a slightly different position on at least half of them, and that would also be true of the groove in the camera back. However, it is very easy to run another groove in the camera back to accept a holder with a different rib-lock.

Unfortunately not many people are aware of the lack of standard in most ULF formats, 11X14 and 14X17 being the exception, but even with these formats there are some very old cameras that were made before ANSI came into being.


Best,

Sandy

 

[sanking]

Wouldn't it make sense, since there are so few people making the holders, to organize and agree on a standard size holder for each format?

Perhaps, and Canham has posted some film holder specifications to encourage standard sizes and it has been our intention to adop them. However, Canham specifications are not stated the same way we expect form the ANSI specifications. For example, in ANSI literature the distance from the end of the film holder to the rib-lock is measured to the far side of the rib-lock, whereas the Canham measurement is to the near side of the rib-lock. A misunderstanding on this issue resulted in us making two batches of holders that just miss the speification. Not a big deal because the groove on the camera back can easily be adjusted, but the problem was not one we anticipated. There is also the issue that changing from one size to another involves compatibility issues for persons who purchased our holders in the past.

Also, I don't expect that Lotus will change their manufacturing process to adopt the Canham specifications, and then there is a very large base of used Korona cameras out there. Also, some holders are being made in China, and most of those appear to be to Lotus specifications.

Sandy

 

[Monophoto]

Wouldn't it make sense, since there are so few people making the holders, to organize and agree on a standard size holder for each format?

In other industries, standards have emerged as a way to bring a degree of order out of the chaos that exists when there are many suppliers offering products and where buyers make purchasing decisions based on price and delivery. In that situation, products from different manufacturers need to be interchangeable and able to work together. That's called a commodity market.

There aren't very many suppliers in the ULF industry, and it seems to me that the products are a long way from being commodity products.

Frankly, what standardization of ULF holders would do is make it possible for low-cost third party suppliers to enter the game and make it a commodity market. I don't see a lot of incentive for the existing manufacturers to want that to happen,.

Frankly, users may not want it either. Part of the allure of ULF is that the equipment is the craftsmanship that goes into cameras and holders, a level of craftsmanship that often parallels the exquisite photographic work for which it is intended. Can you imagine universal (one size fits all) injection molded plastic holders rather than holders custom-crafted from fine hardwoods?

 

[Richard T Ritter]

To get a Lotus holder to match S & S holders just cut 1/8 inch off the film loading end. and retape. This will keep the film center to the ground glass.
The cameras I have been building and repairing are all to the S&S holder spec.

Richard Ritter

 

[barryjyoung]

I'm certainly no expert here, but from what I've read it is more cost , time and quality effective to have an expert build film holders rather than to make them at home; but I'm sure where there is a will there is a way.

Don Bryant

Hi Don:

Yes, truer words, truer words. It has taken me almost a year to design a film holder, basically construct a computer controlled milling machine and track down all of the materials required to make film holders. I am awaiting the final piece of the puzzle now. When it arrives, it will take a few weeks to get into production. I have to write the programs to cut all of the pieces, and make all of the fixtures, but there will soon be a somewhat different film holder on the market. I am also going to be proceeding with the camera prototyping. I have learned two things very well from setting up to mass produce film holders.
1. Making a camera is very much easier than making a film holder.
2. starting a manufacturing business is a series of obstacles to overcome and allowing any of them to stop you will indeed stop you. In other words, your words, where there is a will there is a way.

 

[barryjyoung]

Thank you Sandy King and everyone else who has contributed to this thread, you have helped me so much that I cannot even begin to thank you enough.

 

[Jim Chinn]

The problem with ULF holders is the bizzare and ancient measurements that require a lot of expensive tooling. When I built my ULF cameras I simply adopted different measurements that were easily standardized. By using a T-dimension of .5" I could make holders from .5" komatex plastic and .90 aluminum suptums. I use garolite for slides and the standard fingerstock arrangement for the light trap. I also use a special double sided tape from 3M to hold the film in place, thus eliminating the need for a hinged end. That also allows me to use the same film holder for a variety smaller formats, thus eliminating the need for carrying a reducing back. The cost for those holders if I sold them would be about $150 for a 12x20 as opposed to over $400 for standard holders.

When I was starting to design ULF cameras for sale I had the idea that I would provide 2 holders of this design with each camera. Extra holders would cost about 1/3rd of standard holders. But LF photographers are resistant to change. Most folks I talked to would rather have a camera that uses standard holders regardless of the extra cost.

So after a long delay due to family health issues I am hoping to get that project back on track this spring. But I will be building the cameras to use standard holders. And that may not be such a bad idea, since it sounds like between the Chinese and others in the states there will be a variety of sources for holders.

 

[artedetimo]

In the middle of a build now

This thread has proved invaluable to me in my build project, so thank you all.

I'm building a 12x20 from scratch, loosely based on a folding field camera design, used by the pro builders out there. I say loosely because I haven't actually seen one outside of pics on the web, but they are providing inspiration for the mechanical parts of the camera. I have access to a great shop, so I figured I would take advantage of it. I'm building the whole thing out of cherry, and aluminum, with holders out of cherry, alum, and phenolic for the slides and septum.

I am blogging the process here: http://cameras.artedetimo.com/
and am in the middle of the film holders right now. I tried a slot cutter so far and I think I have something workable for now. If it turns out I need more precision I will probably have to learn to use the mill.

 

[Ray Heath]

g'day Joe

i've built several film holders from scratch from my own design

to use the word design infers a plan, i actually made it up as i went

they don't look the best, they have no high tech aspect, but they work

Ray

 

[Jim Fitzgerald]

Ray, nice job! Where there is a will there is a way. Building holders is a process that needs to be done slowly and carefully. More precise work than on a camera. It can be done but is much slower. I have not built any yet and may never. I am about half way through my Walnut 11x14. Left over wood from the 8x20 a good deal on a perfect fitting bellows and an old Dorff back are speeding up the process. I've got 3 holders now and that may be enough. If i need more then I may tackle this process.

Jim

 

[Rob Vinnedge]

Wouldn't it make sense, since there are so few people making the holders, to organize and agree on a standard size holder for each format?

Greg,

There has been a lot of discussion about the need for film holder standards on the two forums, including a thread, "ULF film holder standards", in the FEEDBACK and DISCUSSION category on this forum. It was my suggestion that we use Sandy King's specifications, which he was generous enough to post in that thread. Another contributor offered a schematic as a reference tool. Sandy, AWB, and Canham seem to be the the leaders in standardization at the moment, with Lotus, Chamonix, and Wisner being the oddballs. Although, to be fair, Chamonix's Hugo Zhang has said that they are aiming toward Sandy's specs.

I truly hope we can arrive at a definitive set of standards soon. New equipment is appearing every day, including a camera that I am designing. Interchangeability of accessories and the resulting ease of manufacture is good for all of us.

 

[Rob Vinnedge]

In other industries, standards have emerged as a way to bring a degree of order out of the chaos that exists when there are many suppliers offering products and where buyers make purchasing decisions based on price and delivery. In that situation, products from different manufacturers need to be interchangeable and able to work together. That's called a commodity market.

There aren't very many suppliers in the ULF industry, and it seems to me that the products are a long way from being commodity products.

Frankly, what standardization of ULF holders would do is make it possible for low-cost third party suppliers to enter the game and make it a commodity market. I don't see a lot of incentive for the existing manufacturers to want that to happen,.

Frankly, users may not want it either. Part of the allure of ULF is that the equipment is the craftsmanship that goes into cameras and holders, a level of craftsmanship that often parallels the exquisite photographic work for which it is intended. Can you imagine universal (one size fits all) injection molded plastic holders rather than holders custom-crafted from fine hardwoods?

I do see your point, that some manufacturers may want to remain proprietary (Lotus?), but frankly, one reason I chose not to go with Lotus was that it limited me. I would not have chosen Wisner for the same reason (a wise decision in retrospect).

Regarding users' needs, a cheaper, one size fits all holder might be desirable, given that there are already enough exquisite pieces of equipment to purchase in the ULF world. There will always be a market for Sandy's holders for the reason you describe. I, for one, want a camera that will accept them, as they appear to be emerging as the new standard.