120 film does not wind tight enough to prevent light leaks

[cxc]

I shoot 120 mainly in pinhole cameras. These cameras are

professionally manufactured (see zeroimage.com), with generally

impeccable results, but they are admittedly very lo-tech, made of

wood and brass and springs.

 

My problem is that occasionally a completed roll will emerge from the

camera too loosely wound, with some of the film/paper extending

beyond the edge of the spool, resulting in light leaks. I can work

around this by unloading in the (relative) dark, then hand-tightening

the roll job. Better yet, can anyone think of what is to be done to

prevent this from happening at all?

 

Interestingly, this problem seems to happen much more often with Fuji

film (NPH 800) than with Kodak (Portra VC 400). I also wonder if

maybe the take-up spool design may be in play, maybe one brand is

more reliable than another?

 

Any thoughts? Wild guesses?

 

TIA,

 

CXC

[douglas_green1]

In most 120 cameras, when the film is inserted into the camera, it is put in a chamber where there is reverse tension, or else significant reverse friction on the film spool, that acts in opposition to the tension on the take-up spool. This not only serves to help keep the film flat, but it insures that the film that is wound onto the takeup spool is wound tightly. I would bet that the simple cameras you are having problems with are not sufficiently tensioning the film spool, but rather, it is sitting reasonably loose in the spool chamber. BOTH spools need to have sufficient opposing tension in order to insure that the film is tightly wound onto the takeup spool.

[pok_hon_wally_yu]

One thing you might want to experiment is to install a film pressure plate that rests against the unexposed film spool. Loop-side Velcro should do the job if your camera allows that experiment. The plate will keep the film taut.

[stephen hazelton]

This is one of the problems they have on Holgas- normal fix there, I understand, is to stick a piece of thin cardboard under the end of the spool.

[h._p.]

A really low tech fix would be a piece of foam glued into the feed chamber so that it presses on the feed roll. Not pretty but I knew a chap who did this in a Rollieflex when the feed tension became eratic in exactly the way you describe. Worked fine for him.

[al_kaplan1]

Back in the 1930's and 1940's there were a lot of really high quality (by today's standards) cameras for 120 film. They had qualty film wind, good pressure plates, and tension on the feed roll as well as shutters with time exposure and a few instantaneous speeds. It would be very easy to unscrew the lens elements and insert a pinhole aperture. If you feel really rich you could pick up a Hasselblad equipped with a microscope shutter and add a pinhole. I've never removed a loose roll from a 'blad magazine!

[jbq]

Yup, sounds like film tension. The cardboard/foam/velcro trick should work...

[j.w.]

Yep, supply-spool back tension, or lack thereof, is the problem. I've built numerous pinhole cameras. My 120 has the same problem. Since the Zero 2000 provides for manual control of both spools via the two brass, knurled knobs, why not try imparting some manual back tension to the supply spool as you advance the film. The film should feel almost "stretched", or "tight" as you advance it.

 

As for the difference between Fuji and Kodak, perhaps the Fuji uses a thicker polyester film base, which, being stiffer, tends to not curl as easy around the spools. Or maybe there's a difference in thickness between the paper backings.

[cxc]

Thanks for the replies. Actually, the camera has bent strips of metal next to each spool slot, which I take it are designed to press against the roll to hold it tight. I'll see if I can't bend 'em a bit more to increase the pressure.

 

CXC

[roger krueger]

You mention Fuji and Kodak; is there any Ilford in your mix?? On my Mamiya Press, Fuji film onto a Fuji spool works fine, even a Kodak spool usually works, but Fuji film onto an Ilford spool is uniformly a mess.