Questions and grain

Dan Margulis <76270.1033@...>

Gary writes,

Thank you all for your constructive comments about my color settings.
Some of you mentioned "learning the numbers". I need to know what
this means. and is the subject covered in Dan's book Professional
Photoshop 6?>>

"By the numbers" is the foundation for all successful color correction. In
its simplest form it implies setting an arbitrary light and dark point
somewhere in the image, and correcting all colors that one would expect to
be neutral to be neutral in fact. These are areas where the human visual
system is rather poor in evaluating what it sees, so the assistance of the
Info palette is necessary.

"Learning the numbers" is essentially a bogeyman erected by those who would
like to make successful color correction seem more difficult than it is.
You will hear people say things like, "that Dan Margulis, he can look at a
tree and know that it's supposed to be 53c18m75y. You'll never be able to
do that! What you really need is a calibrated monitor."

In reality, all that one needs to be able to do is to read a value and know
which color--RMBCGY--is being produced. When someone who knows what he's
doing sets a colored object to certain values, it's almost never because he
knows what values are correct, but rather because he's found values that
couldn't possibly be right and has decided to change them to ones that
conceivably could be.

In the example above, I might have originally found, say 40c30m80y. Now,
contrary to what you might hear, I have not memorized values for particular
trees. However, it's not too much of a stretch to insist that a tree should
be *green*. 40c30m80y is not, it's a greenish yellow. Therefore, it has to
change. 53c18m75y *is* a green. It might not be the right green for this
particular tree, but it has to be better than leaving it yellow.

I also recently had a costumer return a print I had enhance because
it was too grainy. The picture was shot on 800 speed film pushed to
1600. The mistake I made was to set the amount too high when I
unsharpened. Not only did the picture look grainy. ther was a color
shift in the grey horse that gave it a blue twinge.>>

If the picture looks grainy, then the mistake is too low of a Threshold,
not too high an Amount. If the Amount were too high, you'd see flecks of
white and black.

If there is a color shift as a result of sharpening, this can be avoided by
sharpening in the L channel of LAB, or, if working in RGB or CMYK, by using
Edit: Fade>Luminosity directly after applying the sharpening.

Dan Margulis

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