How big is 5x7 film? 8x10 film?

[MartinP]

Any engineer that trusts his suppliers to follow a standard is, to be polite, naive.

This statement implies only one possible solution, that you must make and cut your own film to suit your tanks. This has the implied task that you must also make and sell your own film-holders. You seem to be telling us that you have not heard of any ISO / ASA / BSI standards system?

Relevant standards exist and are followed in a practical manner by other manufacturers. I'd suggest that your tank-sizes are made to suit each group of metric/imperial holders with the same external dimensions, and that the internal part of your tank is then specific to an ISO film size, or British Standard for 'Plate' sizes, with appropriate allowances for tolerances etc. Trying to cope with every badly cut film, made fifty years ago, in a place no-one has ever heard of, is not the way forwards to designing a sane product. You could always offer an adjustable developing-holder for out-of-tolerance sheets if you felt it worthwhile, of course.

 

[tim48v]

I guess I need to be more clear: we're not building a film holder for a camera; we're looking at building larger versions of our SP-445 processing tank and need to know min/max film width for those holders.

Yeah, there's a spec (BTW, it's $85). We already have proof that not everyone's followed it.

 

[Bill Burk]

tim48v,

I know what you're going through. Good luck in your quest.

I once cut a 4x5 negative carrier to fit "real" 4x5 film because I wanted to have the black border but not have the film fall out.

I thought I had found the specification and worked from it, but in my notes, I see I actually measured a piece of film (the film I measured is taped to my notes).

I measured a 4x5 sheet of TMY-2 as 3.918 x 4.925, which was short about 5/64" on each dimension (close to 21/256" on the 4 inch dimension and 19/256" on the 5 inch dimension)... Shy on each dimension from actually being 4 x 5 inches.

So what you have to do is consider the +/- tolerance for trimming, because you want your system to work within these tolerance.

And you should consider any dimensional stability, shrinkage due to temperature, age, humidity and processing...What can that amount to? 0.5%?

I had to deal with the smallest expected because I didn't want the film to fall through... But you have to account for the biggest expected dimension.

 

[tim48v]

I have implied nothing, I have clearly stated that any engineer worth his salt will verify all important details.
I have also stated, numerous times, that we are well aware of the ISO standards. We also know that manufacturers aren't always following them.

What really concerns us is that with over 500 views, not one person could spend one minute to measure one sheet of film. (Except for Mr Burk, who understands the issues with 4x5.) The CFO and marketing guy are seriously questioning how much interest there really is in a larger format system.

This statement implies only one possible solution, that you must make and cut your own film to suit your tanks. This has the implied task that you must also make and sell your own film-holders. You seem to be telling us that you have not heard of any ISO / ASA / BSI standards system?

Relevant standards exist and are followed in a practical manner by other manufacturers. I'd suggest that your tank-sizes are made to suit each group of metric/imperial holders with the same external dimensions, and that the internal part of your tank is then specific to an ISO film size, or British Standard for 'Plate' sizes, with appropriate allowances for tolerances etc. Trying to cope with every badly cut film, made fifty years ago, in a place no-one has ever heard of, is not the way forwards to designing a sane product. You could always offer an adjustable developing-holder for out-of-tolerance sheets if you felt it worthwhile, of course.

 

[MattKing]

I think you might get a better result if you asked a different question.

In fact, I think you actually asked a different question than the one you wanted answered .

It seems to me you are looking for information on real world size variance, not on what each manufacturer's size specification is.

That variance information is the sort of information that a poll of users can contribute to. So ask the moderators to close this thread, and start a new one with that question instead.

 

[Kilgallb]

Why not buy a small box of each and measure it yourself so you're not taking someone else's word for it?

If you buy a box and measure it all you will know is the dimensions of the film in that box. Other lots will vary.

I bet Ilford technical support would answer the question for you.

 

[Bill Burk]

Thanks,

I don't think you need measurements more precise than, say 1/64 inch or maybe 0.005 inches, just some good honest measured examples (maybe with the brand name of the film), taken from some actual sheets of film from a few people's collections...

I'd be happy to help if I had some, but I only have examples from 4x5 and smaller formats.

 

[tim48v]

Bill,
That's exactly what we were looking for! Heck, measure to the nearest mm. For example, the samples of 8x10 I have measured, range from 200.5mm to 202 mm and I doubt anyone is making film larger than 203mm (8"). We could just set our film holder at 205 mm with 4 mm "fingers" and probably be fine. Until someone finds a film that is 197mm. (Which is what happened with our SP-445; there is one manufacturer that is cutting their film too narrow and we had to modify our mold at the last minute. It still just barely stays in the holder.)

Haven't measured any 5x7 yet but I suspect the margins are about the same.

 

[John Bradbury]

In this video you can see all the formats side by side. Quite a good video