Re: YCbCr
Re: YCbCr
- Subject: Re: YCbCr
- From: Dan Reid <email@hidden>
- Date: Sat, 07 Jul 2007 09:51:13 -0700
- Thread-topic: YCbCr
on 6/26/07 1:25 PM, Scott Ettin at email@hidden wrote:
> Marco,
>
> I run a digital media services department at Postworks in New York City.
> Clients give us their SD & HD tapes and we often get requests for image
> sequences, notably TIFF & TARGA files.
>
> We use an AJA Kona 3 card in our Quad G5s to 8 & 10-bit uncompressed
> Quicktimes and then export stills after capture.
>
> The reason that I wanted to see a YCbCr profile in Color Sync is because
> those still images exhibit dramatic chroma and luma clipping.
>
> When I use Maximum Throughput's Sledgehammer, there is no resampling of
> color and luminance.
>
> I'm trying to understand why. I have read this from Apple's Quicktime
> Developer page:
>
> http://developer.apple.com/quicktime/icefloe/dispatch027.html
Hi Scott,
YCbCr is not too different from LAB used in most ICC profiles as LAB is
a color under/over color system. You could use a LAB color space ICC profile
if you want to continue to think and work in a similar color model. Back in
the day I am remembering Kodak had a YCbCr ICC profile included in the
ColorFlow product for digital cameras. Maybe I am remembering wrong.
To convert supplied graphics to SD or HD there are some generic ICC profiles
that you could try. Use the SMPTE-C.icc profile for SD output. The NTSC ICC
profile does not really describe the typical SD TV, hence SMPTE-C adoption
in the 80s.
For HD work you might consider using the sRGB color space. The sRGB ICC
profile uses the same white point and gamma function as SMPTE-601. If you
look closely you'll also note that the primaries of sRGB are ITU-709-2 too.
That should help in minimize clipping when using images destined for HD.
PS. You can apply these ICC profiles using a Quicktime "filter" to objects
in Quicktime compatible software.
--
Dan B. Reid
RPimaging, INC
Color Management Products and Training for Print, Internet, and Motion
Graphics
http://www.rpimaging.com | Toll Free: (866) RGB-CMYK
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