From: Ed Stander (glassact@compuserve.com)
Date: 10/28/01-06:45:11 PM Z
Sandy:
In a typical StepTablet, each step is .15 D apart. Since .3 D is one
f/stop (or twice the exposure time), this would be an easy way to compare
results. In other words: 2 steps (.3D) would indicate that twice the
exposure would be necessary to attain similar density values.
As for the rationale in using Dmin, I would imagine that it lies in the
ease of visually defining Dmin. While black is a relative term (one
person's black is another's dark grey), most would agree that one shade is
perceptably darker than no shade at all.
I, myself, would prefer to base exposure values on middle grey (.73D),
which usually lies in the straight section of the printing scale - but then
what do I know???? Cheers, Ed.
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