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In the July issue of the D-Max Newsletter, Phil Davis wrote a most interesting article on low contrast film-developer combinations. My question is about how the effective film speeds were determined. My understanding (which may be quite wrong) is that, even with a properly calibrated test setup (as described in the Personal Reference Speed Point article elsewhere on this website), it is ordinarily necessary to feed the plotter program curves with high enough Gbars to allow it to generate the ISO triangle. But surely it would not be practical to, for example, develop Fuji Acros 100 in DI#13 for long enough to get a curve with a Gbar of .62!
It would, of course, be very convenient if there were an easy way to generate EFS data for low contrast combinations. If, for example, one found that he needed Gbars lying just below the the lowest Gbars generated by his normal film developer combination, one could try developing just three test films at a higher dilution. But would such an abbreviated supplemental film test produce the necessary data?
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