I'm trying to figure out how the film speed ratings of the 40's & 50's would relate to the current ISO ratings.

I think in the 40's Koday, Weston, and GE speeds were used:

200 Kodak = 40 Weston = 32 GE.


My question is what would Kodak 200 be equal to in the current ISO standards?

I also understand that around 1960 B&W film speeds were doubled to remove the 1 stop saftey factor that had been built in the ASA standards, which confuses the ratings further.

Thanks for your help.

Quote:

On 2004-06-08 07:17, aoresteen wrote: I'm trying to figure out how the film speed ratings of the 40's & 50's would relate to the current ISO ratings. I think in the 40's Koday, Weston, and GE speeds were used: 200 Kodak = 40 Weston = 32 GE. My question is what would Kodak 200 be equal to in the current ISO standards? I also understand that around 1960 B&W film speeds were doubled to remove the 1 stop saftey factor that had been built in the ASA standards, which confuses the ratings further. Thanks for your help.

IIRC 80 weston equals 100 ISO. Or it might be the other way around. I'll check later today. Once you know ISO to Weston you can use that to get Kodak.

The "Focal Encyclopedia" has a table comparing older film speed scales to the then (c. 1969) prevalent British Standard/American Standards Association values. Weston 80 is (more or less) the same as ASA 100.

I had not been aware that Kodak had its own system, but then, I don't know when the ASA published its first standard. I seem to recall that the change in ASA sensitometric criteria took place a bit before 1960 -- I remember "Tri-X" being rerated from 200 to 400, but I don't remember just when; I'd guess 1958 or 1959.