Greg "Blank" - Lizard King. wrote:
In article .com,
"Steven Woody" wrote:

given a characteristic curve of a slide ( netgative ), what density
value corresponds to 18% grey? some one said it is the D1.0, some
others said it is D0.75, which one is right and where these magic
numbers come from ?

thanks.

They aren't magic just based on sensitometry. If you get books written by
Phil Davis "BTZS" or various books by Zakia and Todd you should have a
better understanding. BTW I opt for .75

in my country, i can not find the book :-( can anyone please to
explain the original question for me ?

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