Film Base Thickness Change for Kodak Sheet Films?

Doremus Scudder · Mar 8, 2009

In a recent thread on new T-Max 400, Jerold Harter remarked that he thought the film base to be thinner than the older version.

Recently I developed a largish batch of Tri-X (150+ sheets) and noticed that some of the films seemed to have a thinner base than others. The thinner ones were the newest and were purchased at a camera store in Las Vegas (I was running low...); they came in 25-sheet boxes. The thicker-base films that I was used to came in 100-sheet boxes and were purchased from Freestyle. These were likely older, but still the newest version of Tri-X (i.e., from the new coating plant).

My question: Has anyone noticed of heard of a change in base thickness or material for Kodak sheet films? If so, do you know the difference and, importantly, if there will be any focus issues due to thinner film? (If I were home, I'd get the trusty micrometer out and measure the films in question, but I'm in Europe till mid-June and don't have the film in question with me...)

It is possible is that the film is just more flexible due to a change in base material or coating and not really thinner, just "floppier." Has anyone any information on this?

Just curious...

Best,

Doremus Scudder
www.DoremusScudder.com

alanrockwood · Mar 8, 2009

If anyone has a vernier caliper and sheets of old and new film they could answer the question. I have a caliper, but not the film to do the measurement.

Doremus Scudder · Mar 8, 2009

Alan,

I'm hoping someone in the community here, who has noticed the same thing and has access to a micrometer will do a quick measurement or two and lay the issue to rest. The film in question was definitely flimsier feeling (i.e., not as stiff) as the "normal" film I was used to. It could be thickness or something else like a change of base material, coating, etc. Let's hope someone out there has some of the flimsy film and a micrometer and can do the measurements.

Best,

Doremus Scudder
www.DoremusScudder.com

trexx · Mar 8, 2009

take 10 sheets, developed, of each and and compare. If you cannot tell by eye with ten then I would call it natural variance.

sanking · Mar 9, 2009

Last year I did a couple of articles for View Camera magazine, one comparing TMY to TMY-2 and the other comparing TMY-2 to TMAX-100. All of the tests were done with 4X5 film.

I just measured the thickness of all of the negatives. TMY, TMY-2 and Tmax-100 all measured between 8 and 9 mil thick. I had some TMY and TMY-2 in 5X7 size and both also measured between 8 and 9 mil thick.

Given the complexity of the machinery used in the coating operation it seems highly unlikely to me that Kodak would have made a run of film on anything but the standard base.

BTW, I also tested a sheet of 4X5 TRI-X 320 from a box of very new film and it also measured between 8 and 9 mil.

Sandy King

Doremus Scudder said:
Alan,

I'm hoping someone in the community here, who has noticed the same thing and has access to a micrometer will do a quick measurement or two and lay the issue to rest. The film in question was definitely flimsier feeling (i.e., not as stiff) as the "normal" film I was used to. It could be thickness or something else like a change of base material, coating, etc. Let's hope someone out there has some of the flimsy film and a micrometer and can do the measurements.

Best,

Doremus Scudder
www.DoremusScudder.com

Martin Aislabie · Mar 9, 2009

I have found the film base of any sheet film varies considerably.

It can be quite confusing in the dark trying to peel apart what feels like 2 sheets of film only to find (after several minutes of effort) that it is just a particularly think sheet of film

It is more likely to be batch to batch variation in base thickness than any conscious decision.

As Sandy says - coating is a highly complex process and any strategic changes require huge amounts of effort to revalidate the process

Martin

sanking · Mar 9, 2009

Martin,

I may not have been clear. I just measured many sheets of film of different types and found there to be no difference in thickness at all. By far most of the thickness is in the estar type base that is used, and that all appears to be about 8 mil thickness. I don't know the actual thickness of the emulsion itself but I would doubt that it is much over one mil thick so most of the thickness of a sheet of film is in the base, not in the emulsion.

I am saying that there is very little variation in the actual thickness of sheets of film all coated on the same base, not there is a lot of variation.

Of course, not all emulsions are coated on 8 mil base. My comments were only meant to apply to the films I tested, TMY, TMY-2, Tmax-100 and TRI-X 320. All of the sheets I tested were almost exactly the same thickness.

Sandy King

Martin Aislabie said:
I have found the film base of any sheet film varies considerably.

It can be quite confusing in the dark trying to peel apart what feels like 2 sheets of film only to find (after several minutes of effort) that it is just a particularly think sheet of film

It is more likely to be batch to batch variation in base thickness than any conscious decision.

As Sandy says - coating is a highly complex process and any strategic changes require huge amounts of effort to revalidate the process

Martin

MattKing · Mar 9, 2009

Just thinking out loud here...

Could the perception of variation be due to variation in the flexibility of the base material, rather than the thickness? Does it vary?

Could that be due to variation in temperatures?

Matt

sanking · Mar 9, 2009

Matt,

I would think that Kodak would be using the same base for all of these films, and that there would not be much difference in flexibility, or in other important characteristics.

But that is just speculation on my part. What I know as fact is that all of the films I measured were the same thickness and appeared to have the same flexibility.

Sandy

MattKing said:
Just thinking out loud here...

Could the perception of variation be due to variation in the flexibility of the base material, rather than the thickness? Does it vary?

Could that be due to variation in temperatures?

Matt

Doremus Scudder · Mar 10, 2009

Sandy,

Thanks for the report. I, too, could not understand why Kodak would want to change the thickness (or even the flexibility characteristics) of their film base. However, the difference was quite noticeable. I was developing new Tri-X 320 from different boxes, and the most recently purchased bunch of negatives were decidedly more flexible (flimsier); I felt they were thinner by a very small amount. Possibly my sense that the base was thinner was founded on the difference in flexibility. This could be caused by manufacturing variance or a slight revision in the base material composition that does not significantly affect the thickness.

All the negatives processed just fine, but I was curious if anyone else had experienced this. I wasn't really concerned, however, there was a nagging thought that if the film base were indeed thinner, and if it was not intentional, that focusing might be marginally affected. I'll have to drag out my micrometer when I get back to my Oregon headquarters in June and check.

BTW, I'd love to read your View Camera magazine articles. For some reason, I can't seem to get them to send me any, even though they take my subscription payments... I've e-mailed to no avail. Strange, since I've contributed to the magazine as well. Let me know what month your article was in, and I'll try to find some back issues on e-bay or somewhere.

Best,

Doremus Scudder
www.DoremusScudder.com

sanking · Mar 10, 2009

Doremus,

The articles are A Comparison of T-Max 100 and 400 Film, View Camera, May/June 2008, 62-68, and TMY vs TMY-2: A Comparison, View Camera, March/April 2008, 48-52.

Steve Simmons put these two articles in the subscribers section on line and I believe they are still there so if you know your password and key you can read them on line.

Sandy

Doremus Scudder said:
Sandy,

Thanks for the report. I, too, could not understand why Kodak would want to change the thickness (or even the flexibility characteristics) of their film base. However, the difference was quite noticeable. I was developing new Tri-X 320 from different boxes, and the most recently purchased bunch of negatives were decidedly more flexible (flimsier); I felt they were thinner by a very small amount. Possibly my sense that the base was thinner was founded on the difference in flexibility. This could be caused by manufacturing variance or a slight revision in the base material composition that does not significantly affect the thickness.

All the negatives processed just fine, but I was curious if anyone else had experienced this. I wasn't really concerned, however, there was a nagging thought that if the film base were indeed thinner, and if it was not intentional, that focusing might be marginally affected. I'll have to drag out my micrometer when I get back to my Oregon headquarters in June and check.

BTW, I'd love to read your View Camera magazine articles. For some reason, I can't seem to get them to send me any, even though they take my subscription payments... I've e-mailed to no avail. Strange, since I've contributed to the magazine as well. Let me know what month your article was in, and I'll try to find some back issues on e-bay or somewhere.

Best,

Doremus Scudder
www.DoremusScudder.com

Film Base Thickness Change for Kodak Sheet Films?

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