DanPhoto@aol.com
Tue, 12 Jan 1999 00:52:38 -0500 (EST)
Dave said:
>Just think of a chess board with high Dmax and clear area. Now shrink the
>checker board into 1/2 its size. It still has the clear area and the Dmax
>area. Shrink it 100 times, it still has the clear area and the Dmax area. If
>it is 50% covered, it should have a density of 0.30, but it is NOT the
>same as
>a continous-tone negative with a density of 0.30. A clear understanding of
>this will help you a lot in succesfully printing a digital negative.
I agree.
There are two factors which will affect how a digital negative responds
to both exposure and contrast controls when printed:
1. Dot size. The smaller the dot, the more likely some dot undercutting
will take place. That is, some sensitizer (or emulsion) between dots
(actually UNDER the dots when you think about it) will get partially
exposed. It's these partially exposed areas that help return the feel of
traditional photosensitive response to the printing behavior. Without
them, the sensitizer is treated to an all-or-nothing experience owing to
the digital negative's black dot/clear film structure.
2. The quality of the exposing light. Fluorescent banks that are just
above the negative provide a diffuse light that helps the dot
undercutting. Introducing an optical spacer (mylar) or printing
emulsion-up (two less dust-gathering surfaces to worry about) further
promotes the formation of gray values between dots. Mercury vapor and
other lights suspended far from the negative provide a collimated light
that doesn't make for dot undercutting. If all this stirs memories of the
Callier effect in projection printing, you're thinking in the right
direction!
Remember, even traditional negatives are made up of nothing but black
silver specs and clear film. It's their tiny grain size and random
spacing that gives these negatives the tonal smoothness AND printing
behavior to which we've grown accustomed.
Dan
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