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Re: Custom Curves

>Can anyone offer insight into practical uses of the Custom Curves feature?
>have used it to soften the effect of very strong key lights, and with

Here are some ideas.

If you set the curve to look like the inverse of the typical film curve
you'll be able to make tape look like film.  The first 25% of the curve
should look logarithmic (bump towards white), followed by a linear portion
of about 50% and the remaining piece exponential (bump towards black) all
the way up to white.

A black stretch effect would have a bump towards white in the lower 25 to 30
percent of the cuve and linear from there to white.

Solarization-like effects can be had by taking a point about 1/3 of a way
from black and raising it way up to about 80% white.  Then you take the
point that would have been about 1/3 of a way down from white (if the
original shape was linear) and bring it all the way down to near black (5 to
10%).  This curve looks like a very rounded "N".

A cool way to sort-of reduce the visibility of grain is to do the opposite
of the black stretch technique:  take a point about 1/4 to 1/3 of the way up
from black (starting with a straight line) and bring it down a few units.

Midtone compression can be achieved by placing a white-going bump at about
the 1/2 way poing on an otherwise linear shape.

One of the things Custom Curves lacks is the ability to dissolve (morph?)
between curves.  Apparently daVinci is working on this.  Because of the way
custom curves is implemented in hardware, I don't see how they'd be able to
do this on the current product line.  This will probably be a 2K feature.

A trick to simulate a dissolve between shapes is to define the two shapes
you want and save them in two of the custom-curves memories.  Then you
program a dissolve where gamma goes from the desired setting for curve
number one to neutral.  At this point you switch from one curve to the
other --nothing will happen because gamma is neutral.  You then dissolve to
your new gamma setting now using the second curve.


Thanks to A.F. Associates for support in 1998
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