Film thickness

[alexbeare]

Hi all,

Potentially a weird question, but are some 120 films (well, films + backing paper I guess) thicker than others?

I've just started shooting through a box of Foma 100 in my GF670, and I have noticed that towards the end of the roll, it gets harder and harder to wind - by the last two or three frames, I have to apply about as much force as I can muster just to wind it on... to the point that I am worried about breaking something. I've shot about seven or eight different types of film through it, and never had a problem.

Am I just being paranoid and overprotective of my baby (she is so pretty and sleek, but with retro charm!), or is there actually an issue at play here?

 

[piu58]

35 mm film has 120 µm, 120 film 100µm thickness. Some companies make both from the same base. It may be that you have 120 µm MF or 100µm 35mm film.

 

[David Grenet]

Some backing papers are thicker than others. I've not shot Foma in 120 but Shanghai 100 has noticeably thicker paper than, say, Acros. The datasheet for Foma 100 states that the 120 base is 0.1 mm thick.

 

[Alex Muir]

I have also noticed that some 120 backing, and possibly also the film, is thicker. It doesn't travel as easily through the film-transport. I would avoid film that causes the difficult winding that you describe. It must cause extra wear in the mechanism, and possible damage. Alex

 

[Brac]

When Kodak first introduced their T-Max films in 120 roll-film, the base was thicker than other roll films. This caused some problems in some cameras, but later on the base became thinner than then but still seemed a little thicker than others, and maybe still is. I don't know. The information sheet packed with the films used to give the thickness but I haven't bought any for years so can't quote what it is.

Over the years Kodak & Ilford backing papers seem to have got thinner than they used to be.

 

[R.Gould]

The backing paper on Foma films is thicker than either Ilford or Kodak, I use Fomapan 400 in all of my old cameras, from a baby bessa 66 from 1936 to my rolleis, both a cord and flex, and very many folders and have never had a problem winding, with me it certqainly never gets harder as the film advances, except once on my Ensign 16/20, and that was down to me not loading the film correctly, I did not get it straight, and since I learn't my lesson I have never had a problem with any camera.
Richard

 

[eriklovold]

I have the GF670 and I have also had this issue on occasion, but with all sorts of films - Acros, 400H, Portra 400. Sometimes the roll doesn't wind tightly enough, and at the end of the roll it can get really hard to wind on (like you, I have been scared of breaking it). When I take the roll out, the film is so "fat" it bulges out of the spool, causing small light leaks at the edges of the film. My theory was that it's caused by rapid change in temperature.

 

[Douglas Fairbank]

Some years ago I looked into this in great detail. The findings aren't relevant now but what I found was that the film thickness varied as you might expect but the manufacturer compensated by using backing paper of a different thickness so the combined thickness of film and paper was fairly consistent across brands. The international standard for 120 (and 620) film is not a tight as most people might expect and I did have to check cameras with film brands that represented the extremes of variation at the time.
The one bit of advice I would always give was to try to always use the same brand take up spool as the film being used. If the backing paper edge gets gets stressed due to the spool being too narrow or the film not running on to it in perfect alignment this can have a big effect of the force needed to transport the film.

 

[Douglas Fairbank]

When I take the roll out, the film is so "fat" it bulges out of the spool, causing small light leaks at the edges of the film.

This is definitely a problem with the backing paper being stressed at the edges, find the cause and the problem will go away.

 

[gleaf]

The Ilford 120 FP4 in the drawer next to me is running about 0.004 - 0.005 inch with my cheap digital calibers.

 

[alexbeare]

Thanks guys, some great suggestions.

35 mm film has 120 µm, 120 film 100µm thickness. Some companies make both from the same base. It may be that you have 120 µm MF or 100µm 35mm film.

Hm. Makes sense.

The one bit of advice I would always give was to try to always use the same brand take up spool as the film being used. If the backing paper edge gets gets stressed due to the spool being too narrow or the film not running on to it in perfect alignment this can have a big effect of the force needed to transport the film.

I never even considered that the spools could be the issue. I was definitely mixing and matching spools (400H or Porta) when I ran into problems. I'll run the next roll through with a Foma spool and see if it helps.