Old Film Evaluation

Question

I have many rolls of outdated 6x6 cm color negative (print) film. To try and establish a functional ASA, I shot a series of test exposures with my Bronica S2 of a three-stripe card (black/18% (middle) grey/white) - first at metered value of f/8 using the factory ASA and then three stops above and below. I had the film processed (C-22) and commercially scanned to jpg files. In Photoshop, I desatuated the image to eliminate color balance issues so I could measure only the luminance. I assumed tthe "correct" exposure would be the one that yielded a measured 18%/middle grey value of approximately 119/119/119. If my approach makes sense, then I have to conclude that the film has not significantly lost sensitivity and the metered exposure is pretty close - but the white value - instead of being 255 - is depressed on al test exposures. Apparently, there is a gamma issue and the old film has lost contrast capabilities.

First, I need a professional opinion as to whether my evaluation process is valid. Second if it is possible, once I settle on a specific scanned image, I need a step-by-step Photoshop procedure to correct the contrast range so the readings for the stripes on the test card come out to around 4 for black, middle grey at around 119 and whites to around 250.

Please do not hesitate to be critical if my logic is faulty but don't beat me up too bad since I am really old 🙂

D Fosse · Answer

The problem here is the scanning. That introduces a new and totally unpredictable variable into the equation. Establishing a calibration procedure for the scanning again requires a reference negative. The depressed highlights may just as well come from the scanning (and most likely do).

So this rapidly becomes an equation with a lot of unknowns, and I'm not sure it's worth the effort. I think I'd just make some test exposures at nominal ISO (ASA), and see how it behaves.

In any case, with old color film, I'd be less concerned with overall sensitivity, and more concerned with curve inconsistencies per dye - in other words, color casts in shadows, midtones or highlights. I sometimes used old and poorly stored film myself back in the day, and they often turned out to have very weird color casts. I've later tried to fix some of them up in Photoshop with varying success.

EDIT: To be a little more precise: yes, there is a gamma issue, but not because the film is old. Negative film didn't have the same tone response curves as digital files, and they can't be directly translated.

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