You cannot set an ISO (nor ASA) number on an extinction meter.
To use the extinction meter, you need the chart supplied by the maker. There is no standard for extinction meters so no interchangeable chart is possible. With my Braun Paxette, the chart is riveted to the ever-ready case: extinction+meter.jpg You could try this chart - for this chart, it assumes ASA 50 as that was the most common film at the time the camera was made. For other film speeds, you need to mentally adjust - for ASA 100, you close down one stop, for ASA 400 you close down three stops.
You also need to look through the meter for quite a long time to allow your eye to normalise - the instructions with my Paxette suggest 20 seconds! That said, the Braun extinction meter agrees quite closely with my modern digital camera.
You also would need to understand that ASA standard was altered in the mid 1950s so even with the chart a meter (of any type) made in the early 1950s is going to use the earlier ASA standard - a problem I have with my Zeiss Ikon Contaflex - and that would require a further mental adjustment.
Last edited by Peltigera; 05-07-2013 at 06:09 AM. Click to view previous post history.