Quote Originally Posted by AgX View Post
PE,

can you relate ISO Paper speed to ISO Film speed?

In scientific reports ASA Film speeds are given to photographic papers ranging from 1/100 to 10 ASA Film.
Yes, you can relate ISO Paper speed to ISO Film speed.

You expose a series of paper negatives until one is properly exposed and one that will scan properly to form a good reversal image. At that point, you have the ISO. Then you compare that ISO (In-camera) to the paper ISO and begin constructing a conversion table.

OTOH, you have to remember that this is not a true emulsion ISO, as the paper picks up speed from back reflections.

An alternative method, which is much harder, is to do exposures on a spectrosensitometer and then integrate the area under the curve.

I have used both methods. I find therefore that Ilford MGIV paper is close to a true ISO of 25, all things considered such as the high average contrast and the back reflection. I have posted some of that here before.

PE