Quote Originally Posted by MattKing View Post
It would surprise me if the ISO standard speed was the same as the EI used by ZS practitioners.

It surprised me too-----but I began using the results as is and I've been using them for quite a while now and have no reason to argue with them. I test precisely as described here, in short, it's an in-camera exposure of a step tablet contacted to a sheet of 4x5 film, yielding flare-free step data.

Tmax 100 & D76 1:1-------Tmax 100 & XTOL 1:1 tested with the same results:
N+2 EI 125
N+1 box speed
N box speed
N-1 box speed
N-2 EI 80

Tri-X 320 & HC-110(1:63)
N+2 EI 400
N+1 box speed
N box speed
N-1 EI 200
N-2 EI 160