Mac_mcdougald 2010-06-15 18:04:01
Good little history lesson, Grant.
I’ve been photog, mostly paid one, for about 35 years, mostly knew the
score on that stuff (but hadn’t thought of it in a while).
Only meant that actual ASA/ISO speed numbers did stay the same; I would
have thought that once an international standard was instituted, what
with metrical units and all, was a little surprised that ISO numbers
didn’t go to more precise numbers. But Tri-X was ASA 400/ISO 400, Plus-X
125 for both, etc.
Of course, some pro films *do* have additional exposure compensation
factor, as tested for that particular emulsion run, so the “speed” is
just really a “purt good” ballpark figure.