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4-8 PowerColor User Guide
ically. This is because the Cast Correction setting is on Full--The color computer
will always keep the CMY values adjusted based on the Cast setting. The Color
Computer knows the relationship between Cyan, Magenta and Yellow based on
the user definable Gray Balance Table. You have now made the paper white
patch a specular highlight.
For the Shadow point, take the Shadow sticky densitometer and place it on the
Black patch. In the Cyan field next to the Shadow label type “100”. The black
patch will now become the absolute shadow point.
Of course, setting the input range would be a piece of cake if you only have to
scan IT8’s. Unfortunately, in the real world, not all images have perfect specular
highlights and absolute shadow points. But that’s OK, because PowerColor was
designed for the real world.
The next example is closer to the challenges of everyday scanning: Again, lets
use the bottom of the IT8, but this time we are going to throw out every patch
except #3 and #20. Now patch #3 may exist in an image as a linen table cloth,
pearl necklace, shirt, or countless other objects and materials. The point is that it
is identifiable in the image, and we either know, were told, or have to make an
assumption as to how it should reproduce on paper.
Lets start with knowing that patch #3 should be neutral and the cyan dot value
should be 10%. Take the Highlight sticky densitometer and place it on patch #3.
In the Cyan field type in “10” and hit Enter. You have just set a Diffused
Highlight and, because the cyan value is greater than 0, the Catch Light is auto-
matically activated. Now move the Shadow sticky densitometer to patch #20 and
in the Cyan field next to the Shadow label, type “97” and hit Enter.
Note: Highlight and Shadow points don’t need
to be at the extreme ends of a histogram, even
though most of us are taught to think that way.
In fact, the highlight and shadow points don’t
even need to be neutral and in many images
you will need to leave a cast in these points.
Now, change the Highlight Cast correction setting to Half in the Settings Window.
The color computer will automatically calculate and keep half of the original
cast. Change the cast setting to None. The Highlight point will now keep 100%
of its original cast. Set the cast setting to Manual and you can now control the
Highlight point to any values that you desire. This of course works identically for
shadow cast.