Convert CMYK curves to RGB curves???

Discussion in 'Photoshop Tutorials' started by arkarda, Mar 20, 2006.

  1. arkarda

    arkarda Guest

    alright got a problemo! there are a few progs out there that read
    photoshop curves files and duplicate the result in their own curves

    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 , a completely
    different result!
    Very soon I realized it only accepted RGB colorspace as alot of image
    and vdeo tools do.Is there a wave to CONVERT in photoshop or other
    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, Mar 20, 2006
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  2. arkarda

    Mike Russell Guest

    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.
    Mike Russell, Mar 20, 2006
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