I recently developed a few rolls of 120 Pan F and got a few irregular (even jagged) black marks about 1 to 3 mm long in the center portions of the negatives. They do not come off with film cleaner and seem to part of the developed emulsion. Does anyone have ideas what could be causing this. Thanks.

-- Bert Krages (krages@teleport.com), July 27, 2000

Answers

The most likely cause is some form of mechanical damage to the film. Abrasion from rolling the film too tight, or folding marks where the film has kinked while loading the developing reel, are the two commonest culprits. If the marks are crescent shaped, then it's almost cetainly caused by the film being kinked.
Film is delicate stuff, especially 120 size, and you need to take a lot of care in handling it.

-- Pete Andrews (p.l.andrews@bham.ac.uk), July 27, 2000.

I sounds like static electricity. Any time you wind or unwind film fast in a dry environment it can build up a static charge that will eventually discharge and expose the film where it does so. Can cause all sorts of really interesting jaggedy shapes.

-- Fritz M. Brown (brownf@idhw.state.id.us), July 27, 2000.

Most likely it is in the loading when the film is cupped to put on the reel and makes a "crimp" in the film, it tends to break the emulsion and the developer gets in and really over develops that crimp.

-- william cochran (bc555@aol.com), September 06, 2000.

I agree with the static electricity idea. I have three Mamiya M 6s and all of them would produce black marks with 220 film on a cool dry day. The camera actually creates these marks when the shutter is fired. Mamiya replaced the film rollers correcting the problem by putting rubber rings around the film rollers.

-- dudley harris (dudleyharris@mindspring.com), September 18, 2000.

If your film doesn't show any mechanical damage, then it's static electricity. I've only had marks like those when I had a rotten time loading a plastic reel, and the film would bind up, kink, and get bent.

-- Brian C. Miller (brian.c.miller@gte.net), September 18, 2000.