OK I set up and did this test yesterday but the results were inconclusive. Just to be sure I have this straight, I am testing for a film speed bu making 8 exposures between ASA 40 and 160. So I am to meter on my big piece of cardboard for each film speed and close down by 4 stops? Thank you.
Yes exactly. If your results were inconclusive, make bigger differences that will be easier to see: For example you could try EI 3 6 12 25 50 100 200