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Converting from RGB to CMYK alters shadows

Dec 5, 2012 10:03 AM

When working with our product photos, I keep them in RGB and add drop shadows to them by drawing  rectangular marquees on a separate layer, fill them with black and then apply gaussian and motin blur to them. Works quite well. Plus with the shadow on it's own layer, I can turn it off in InDesign if need be. The problem is when I convert the photo to CMYK for offset printing. It's asks if I want merge the layers to which I say no since I want to be able to turn the shadows off if need be, but when I say no, then the shadows get bigger and do not look as good as they did in RGB. If I say yes to merge, then the shadows look the same as they did in RGB but I lose the ability to turn them off in InDesign.

 

Is there a way to keep the shadows looking the same when converted to CMYK without having to merge the layers? Using PS CS6 64 bit. Thanks.

 
Replies
  • Currently Being Moderated
    Dec 5, 2012 10:50 AM   in reply to mc_mark

    I'm not an expert on this at all but have you tried importing the image as a smart object? Other than that use a flattened version saved as a tif and link it to your layered psd so you have an 'original' in case you need to swap out the shadow by creating a un-shadowed version? Just some thoughts...

     
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    Dec 5, 2012 10:53 AM   in reply to mc_mark

    Image > Duplicate and delete the shadow. Convert both documents to CMYK merging the one with the shadow. Drag the one without the shadow and drop it on the other.

     
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    Dec 5, 2012 11:04 AM   in reply to mc_mark

    Keep the files as RGB and place in InDesign.

     

    You can specific a profile to convert to CYMK when printing  inhouse or when exporting a PDF.

     

    But unless you know the exact profile or are provided it by your print shop you should keep the RGB when exporting PDF.

    The print shop will apply the correct profile when printing to their press/printer.

     
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    Dec 5, 2012 11:56 AM   in reply to Bo LeBeau

    The print shop will apply the correct profile

     

    that's a crap shoot here in San Diego, but i would be interested if keeping the files as RGB and placing them in InDesign works around the problem -- i would think any conversion would be subject to the same anomaly that Photoshop is showing

     

    but i don't know... maybe convert to the destination cmyk before setting any layer effects or adjustment layers

     
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    Dec 5, 2012 3:41 PM   in reply to gator soup

    gator soup wrote:

     

    ... i would think any conversion would be subject to the same anomaly that Photoshop is showing

     

    but i don't know... maybe convert to the destination cmyk before setting any layer effects or adjustment layers

    Effects, like gradients, drop shadows, etc are not converted by the color management pixel by pixel because Photoshop doesn't see them as pixels but as a procedure (formula) with key colors for generating the effect in the destination color space. So, for drop shadow, only the shadow color is converted to its closest match in the destination color space but all other parameters affecting the color like the blending mode, opacity, etc are applied in the destination color space which gives different appearance - first, because color space characteristics like gamma curve is different and second in case of a different model (CMYK), the blending of colors is based on entirely different algorithms.

    So, basically effects is best to be recreated in the destination color space or flattened before conversion.

     
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