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Personal Reference Speed Point

Stephen E. Sample

10:02 15 Jun 07

I just did a film test with Fred Newman. The film was Fuji Acros 100, Developer was DD-X at 1+7 at 75 degrees, using 2oz in the tubes. The Effective Film Speed registered at 125 for a 8.33 SBR up to 160 for a 4.67 SBR.

These EFS's seem very high to me, since I have always rated my TMX and Acros at about asa 80 on my pentax spot meter. I do not use the power dial or expo/dev software. I expose using the zone system and would use the method outlined in the 1981 volume of BTZS on page 51 and figure 5-11 for metering and exposing and and figure 5-12 for development.

The Personal Reference Speed Point article by Phil Davis outlines the testing setup and the need for the plotter's gray "ISO triangle" to hit the 2.40 personal reference speed point. On my test the "ISO triangle" is located at about 2.5. The understood the article to say that the test needs to be recalibrated if the curve family "ISO triangle" does not hit the desired 2.4. Fred says it is ok and just use these film speeds. My intuition tells me that I'll get underexposed negatives using the conventional method.

I bought the BTZS Plotter. Can make changes to the setup and get a better calculation? Things just don't seem correct, when I compare this test to the Acros tests in the film library. Thanks for any advice. Steve