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The instruction for using the Power Dial says to set the Power Dial ISO to the nominal ISO rating of the film in use and the meter to the same ISO 100 for my Acros 100 film.
However, my Acros100/DDX 1+7 combination, as tested by the View Camera Store, tests at a PSP of 2.50, which is ISO 125. The standard is 2.4 on the x-axis.
Should I set my Power dial at the ISO 125 instead of the ISO 100 to compensate?
This 2.50 is marked by the 'official' ISO point that appears on the x-axis as a small gray circle and triangle.
In his article "How to read a film test", Phil states that all films do not live up to their ratings, "so we provide a special reference speed point, identified by a dark circle/triangle that represents the 'real' ISO point of the material . (on my plotter this is dark blue and it is located at PSP 2.4) The Plotter compares these two points to determine the practical working speed and film/developer combination for any subject range and development condition. Similarly, the program uses your ES value and the curves' G-bars to calculate the subject ranges.
I have read the BTZS book and viewed the video, yet I don't understand the difference between the "official' and 'real' ISO points and how it is used in the Power Dial and I suppose Expo/Dev program? I'll appreciate any further explanation? Thanks.
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