Aging 35mm film - rating ISO

[razocaine_07]

As film ages, I know that usually rating the ISO differently is recommended.
Is there any method on how to work out what ISO to shoot, say an out of date 100 ISO colour negative film? The threads I've found around the net suggest 64 ISO

 

[Cholentpot]

A stop a decade people say.

I found that slower film, ISO 100 and lower don't really age all that bad. 400 speed will be pretty terrible though. It also depends on storage and the like.

 

[razocaine_07]

That kinda backs up what I've found. I used some oldish 400 ISO lately and it looked terrible.
The film has been kept cool but not refrigerated

 

[Theo Sulphate]

A year or so ago I used several rolls of Kodak Pro 1000 (120-format, ISO 1000) from 1999 at ISO 250. Results were decent; there was some fogging visible in the base, but otherwise not bad.

I'm currently using Kodak Pro 100 (120-format, ISO 100) from 1998 and I'm treating it as ISO 25.

Both of these have been refrigerated (but not frozen) all this time.

 

[Mainecoonmaniac]

I found with film older than a decade, the there's lots of film base fog. If it's not too bad, printing on a higher grade can compensate for that.

 

[Sirius Glass]

If the film was refrigerated or frozen you can safely shoot at box speed.