I recently shot my second expired roll of Kodacolor X from the 1970s. The film was rated at 100 ASA / ISO and so I scientifically decided to run it at ISO 32. The only real usable images I came away with were those where I was compensating for sunlight and I increased the EV 1 full stop. From there I got an image with little, if any, shadow detail. Interesting pictures, but not in any way representative of what I wanted to capture. I would say that with Kodacolor X we should be shooting at around ISO 12. If you use ISO 25 shoot some brackets or do some tests because that might not quite cut it. My C22 chemistry was pretty fresh. I don’t think that had much a’do with it.