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color convert RGB to XYZ


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#1 jin

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Posted 20 May 2008 - 04:10 AM

Hi, I?m Jin. :rolleyes:
I?d like to know how to transform color space exactly.
I?ve studied to convert color space using Apple?s ShakeTM software. [Color and Mastering for Digital Cinema] written by Glenn Kennel is a good guide in my study. I?m doing Glenn Kennel?s method step by step. The book especially was described below a paragraph about a color conversion.
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The color conversion to X?Y?Z? was accomplished using Apple?s ShakeTM software. The digital files were linearized (applying a gamma of 2.6), then a 3x3 matrix was applied to convert RGB to XYZ, followed by application of the 1/2.6 gamma function. The finished color-corrected files were stored as 12-bits X?Y?Z? data in 16-bit TIFF files. This process will be described in more detail in Chapter 7.
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Here, I don?t know which a node of Shake I have to use.
If there is someone who converts color space using Shake, please let me know it.
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#2 Michael Most

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Posted 20 May 2008 - 10:02 AM

Here, I don’t know which a node of Shake I have to use.
If there is someone who converts color space using Shake, please let me know it.


Use the ColorX node and enter expressions for R, G, and B based on the matrix math. Be aware that you need to put the incoming material in at least 16 bit (preferably float) space (use a Bytes node) and linearize it (use a Gamma node with the inverse of whatever gamma the material is in) prior to any matrix transform, and then raise the result back to whatever gamma is required on output (which is basically what Glenn is describing).

The much easier way to do this if you're not really familiar with matrix transforms or color space conversions is to use the color management that's built into After Effects CS3.
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