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Hi there.

Re. Clipping
When someone talks about clipping in the digital domain I get goosebumps. Yes
I know, sometimes there is no remedy but clipping does two BAAD things. It
forever destroys detail, you know that already, but the second issue is worse
since
clipping can very easily produce very sharp edges (risetimes). While this is
in fact not a problem in digital domain it is so as soon as you take your
signal
into analogue (the better the encoder the worse the problem). The reason for
this is simply that in analog domain all filters and signal processing is
designed around a max rise time (as defined in a standard). If it is
exceeded, ringing and other nasties occur. In digital domain the transition
from a
white to black pixel produces about three times greater than permitted
risetimes.
And the more you clip or simply put in detail with HAC/VAC the more trouble
at
the end.

The message is BEWARE.

There are remedies, as I am also a sales guy I am obliged to let you know
that the CSP primary colour corrector has a 95% knee roll off allowing
highlight
compression. Thats one way to do it. If you see us at NAB I will let you know
a few other ways or tools to get around the problem.

Re. Colour space
While I fully understand all you colorists reguirement to know where the
grading is destined to, ie most often composite, you may  want to think about
this
for a while. You are creating a master, no? Do you want to make that master
limited
to yesterdays technology or the one that is closer than you may be fully
aware
of?

In other words if you put composite or RGB colourspace limitations on a
digita lcomponent tape it is useless for digital component releases. Is that
what you
want to put into the archive shelf? In addition, since RGB and composite
colourspaces are not compatible (neither is bigger than the other) you will
have to think even harder whether to make the limitations in RGB or composite
domain.

If you want to read more about this, request or reprint from us "Light
Talks".

See you at NAB

Mike Reichel/Digital Vision


Subj:	ARTISAN
Date:	95-03-01 06:42:14 EST
From:	telecine at xyzoom.alegria.com
To:	telecine at xyzoom.alegria.com