First test is on 35mm stock. I'll upload the 16mm footage next week or so.
This was all very impromptu, I just grabbed a girl that happened to work at the rental house, I had no real lights and nobody to pull focus. So yo have to see past all that. But still interesting.
I purposefully chose the oldest film cans I had laying around, and/or went for the ones with the highest ISO or most corroded can. As you can see in the case of the first example 5283 800ASA stock from 2001, it's almost unusable. This was one of the "flop" stocks from Kodak that nobody liked, and it was only produced between 2001 and 2003. It was considered too grainy even then.
These films were stored for about 3 years frozen, then in various room temperature settings, attics, cellars etc. It was also shipped to the US from the UK, so as you can see, there is some X-ray damage mainly on the 800ASA. Lower ISO films are less susceptible to X-ray damage.
In general, you will see that film loses its sensitivity as it gets older, regardless of it's speed. And by exposing at rated ISO, you'll see that the gamma rays and the decay have raised the base levels up so this is now underexposed. Once you start to get to 2 stops of overexposure, you'll see the film starts to behave a lot better and grain is suppressed.
I bracketed most of the the stocks between -1 and +2 of exposure. In the case of the 800ASA stock I forgot to change ISO setting on my light meter from 200ASA, so that stock is actually overexposed twice as much - meaning, if it says +2 stops it's actually +4. Which still didn't help it much..
In telecine it was not te objective to show the exposure differences, hence the film was normalized to look about the same exposure-wise, so as to easier be able to judge grain levels between the clips. Interestingly, on the vectorscope, the red layer and the green layer (but especially the red) showed the most X-ray/storage damage, whereas the blue layer was almost unaffected. Meaning, if you had to use really old stock that was damaged, you'd be better off lighting it very blue. It would show up less.
Kodak 5283 800ASA from 2001 with X-ray damage:
But here's the most interesting test of them all. This is the oldest can I could find in my collection and it's from 1996. So almost 22 year old film. It was stored the same way as the 800ASA, shipped and X-rayed the same way. But as you can see, it performs much much better. In fact, at +2 stops of overexposure (towards end of clip), it could quite easily be used today. Colors get a little dull and the contrast increases, but all these things could be mitigated if one was so inclined and hell-bent on using it (Varicon, LowCon, pre-flashing, post-flashing etc). Very interesting.
Kodak 5293 200ASA from 1996:
Conclusion for old still film has always been to add a stop of exposure for each decade when shooting expired film. I would say that's conservative when it comes to MP film (where it's storage has been less than optimal). It seems to me that for anything below 200ASA, I would add 1.5stops for each decade. For ISO's above 200, I'd say that should be 2 stops per decade. And for 800ASA, well, as you can see, +4 stops is not nearly enough. I wonder how the grain structure would have behaved at 6-8-stops of overexposure?
I hope you found this little non-scientific test informative. Next week I'll upload the two 16mm filmstock tests I did.