The ISO standard allows the film speed to be test by either the ASA/BS system (which Kodak had relaxed) or the more practical DIN system used by Agfa.
Originally Posted by MattKing
So with Agfa films like APX100 where the speed was tested using the DIN standard my Zone system tests gave me an EI thge same as the ISO speed, and many others found the same. The opposite was true with Tmax100 where I needed to use50 EI instead of the box 100 ISO.
It's also worth remembering that the developer used for the ASA tests gave slightly better film speed and shadow detail than D76.