Radiation effect on exposed film

[al olson]

I recently discovered an exposed roll of MACO 820c while I was reorganizing my camera bag. I developed it yesterday and was surprised at the results. I want to bring this to the attention of forum members because of the implications of long periods without refrigeration as well as the effects of radiation (light? cosmic rays? etc.) might have on old film.

To provide some background, this is a test roll that I exposed 7 years ago. It managed to hide in the recesses of the camera bag that I use for my Bronica and surfaced as I was reorganizing it several days ago. To the best of my knowledge it has never been left in bright sunlight or near other sources of known radiation.

The the film strips show edge exposure throughout the roll. The example film scan that I have included shows a very marked increase in fogging, beginning with frame 7 in the upper right corner and blotting the image nearly completely by frame 12 in the lower left corner. The outermost layers are the ones most affected.

What is unusual is that while it appears that whatever radiation was involved, it was able to penetrate the paper backing, through the film base to the emulsion. However, note from the image that the ink markings on the paper backing appear to have some effect on blocking the radiation.

Of additional interest is the fact that markings on the outer layers are not repeated on the inner film layers, perhaps due to scattering as the the radiation passes through an additional film and paper layer.

If the radiation is capable of penetrating the paper backing, perhaps this fogging may have something to do with the sensitivity of the film in the IR region.

In any event, it is clear that some form of radiation was able to penetrate the paper backing and film for several layers into the roll.

Seldom do I leave my film unrefrigerated for great lengths of time, but this experience also poses the question of how much radiation can penetrate the metal housing of a refrigerator or freezer. Or the cardboard box for sheet film. Since I have a large stock out-of-date film in both sheets and rolls I am more concerned than I had been in the past. Should one be investing in large volumes of film to keep after it has been discontinued?

[Jack Dahlgren]

Radon?

[al olson]

Radon?

I guess that's a possibility. I keep my camera bag on the floor just above the crawl space. If that would be the case, then my film stock should be a little safer since it is in the freezer on the second floor.

It does not appear that one side of the roll got more exposure than the other which would have left a repeating pattern which would happen if the radiation was coming from a single direction.

[Robert Hughes]

I'd guess heat based chemical breakdown was the likely culprit for this roll. If it were radiation, the fogging would be constant across the width of the film frame, or cyclical as shown below, no?

PS I see markings of the paper backing showing on these frames. Interesting, but again, it may have a chemical source.

Here are Kodak images of motion picture film run through an airport scanner: