Re: NTSC video and color management?
Re: NTSC video and color management?
- Subject: Re: NTSC video and color management?
- From: Graeme Gill <email@hidden>
- Date: Mon, 14 Feb 2005 12:46:07 +1100
- Organization: Argyll CMS
Ray Maxwell wrote:
When I create a graphic in the NTSC color space in Photoshop it allows
me to create colors where RGB values go from 0 to 255. If I then run
the "NTSC Colors" filter, the saturated colors, Red, Green, Blue, Cyan,
Magenta, and Yellow are limited to values less than 255. Some are cut
back as far as 170. Note that the color white is still 255, 255, 255.
Is this limiting due to NTSC composite encoding?
That's the idea.
If all of the video production were kept as component video (Y Cr Cb)
could I use the full 0 to 255 that can be reached in the NTSC 1953 profile?
I think if the NTSC filter is doing the right thing, your gamut will be
the same, just the numbers are different. Note that the actual composite
color encoding doesn't use Cr Cb, but uses I and Q, which is a scaled,
rotated version of the color difference signals, and these are bandwidth limited
compared to the luminance signal, further complicating what can be represented
if the filter was doing an accurate job.
I am trying to understand where the bottle neck is in the video
production process. Is it the NTSC 1953 profiles or is it further
restricted by the NTSC composite encoding?
Can anyone point me to a book on this subject?
A good (technical) article to start with is "Television Color Encoding
and "Hot" Broadcast colors" by David Martindale and Alan W. Paeth,
Graphics Gems II, page 147.
A book worth getting hold of is "A Technical Introduction to Digital Video"
by Charles Poynton.
I think Jim Blinn wrote a couple of articles for IEEE CG&A a while back
that covered some of this, and it may have been collected into a book
(check for books by Jim Blinn on Amazon for "Dirty Pixels", although I think
his coverage of NTSC encoding is just part of one chapter).
There are numerous other books on the subject of video encoding, and
and much on line material of variable quality. Googling "NTSC safe colors"
turns up a fair amount of stuff, although I don't think you'll find
much in the way of references to ICC profiles etc., since video and
color tend to be regarded as separate worlds.
Graeme Gill.
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