From: Sandy King (sanking@clemson.edu)
Date: 10/28/01-08:46:48 PM Z
Ed,
>
> 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.
Yes, this is how I make this determination. But this method is of
course inaccurate with POP.
>
> 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????
What I have learned from further reading is that the current
convention for measuring the speed of silver papers is fairly recent.
As late as the early 1970s there was no standard method of testing or
expressing the speed of printing papers,although some manufacturers
did provide information regarding the relative speed of their papers.
Your preference for a base exposure value based on middle grey is not
far from the actual value of the convention of 0.6 plus Dmin since I
assume you are going to have a Dmin of around 0.05 with most papers.
Sandy King
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