Convert CMYK curves to RGB curves???

A
Posted By
arkarda
Mar 20, 2006
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223
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1
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Closed
alright got a problemo! there are a few progs out there that read photoshop curves files and duplicate the result in their own curves facility.
KOOL!

But I was doing something vey intereasting with the CMYK colorspace and saved the result as a curve AMP file.

Loaded the AMP file into the program , and…..got a completely different result!
Very soon I realized it only accepted RGB colorspace as alot of image editors
and vdeo tools do.Is there a wave to CONVERT in photoshop or other software
a CMYK curve into an RGB curve (or as close in RGB colorspace) and save out as an AMP file.

Anybody providing the answer would save my bacon.BIG TIME.

thanks in advance,

arkarda.

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MR
Mike Russell
Mar 20, 2006
"arkarda" wrote in message
alright got a problemo! there are a few progs out there that read photoshop curves files and duplicate the result in their own curves facility. KOOL!

But I was doing something vey intereasting with the CMYK colorspace and saved the result as a curve AMP file.

Loaded the AMP file into the program , and…..got a completely different result!
Very soon I realized it only accepted RGB colorspace as alot of image editors
and vdeo tools do.Is there a wave to CONVERT in photoshop or other software
a CMYK curve into an RGB curve (or as close in RGB colorspace) and save out as an AMP file.

Anybody providing the answer would save my bacon.BIG TIME.

Have you tried to manually get a set of RGB curves that give a result similar to your CMYK result? If you cannot do this reasonably well, the odds are slim that a good conversion is possible.

It is certainly possible to convert your CMYK curve to an approximate RGB curve if it stays within certain limits. The accuracy of the final curve may be limited because CMYK includes a fourth K channel that is not present in RGB mode. If you are performing heavy manipulations on the K channel, the accuracy will be poor because there is no K channel in RGB. Modifying the shadow in RGB generally requires changing all three channels.

FYI. There is another procedure called "curve extraction" that involves curving the image in CMYK, converting to RGB and extracting the curve using Curvemeister’s pinning feature. Photoshop would then be used to convert the curve to AMP format. This may be also be done manually using Photoshop curves with a little extra book keeping.

The following tutorial shows how to use curve extraction to approximate a camera white balance setting. The same technique may be adapted to your CMYK curve.
http://www.curvemeister.com/tutorials/CurveExtraction/index. html
Mike Russell
www.curvemeister.com

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