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ballina@earthlink.net
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Conversion of adobe 1998 profile to CS5 working cmyk then to srgb to proofing 4 press cmyk profile

Dec 1, 2011 6:50 AM

I am working on a book that will be printed by a 4 color press in cmyk.  The printer has given me a cmyk profile for their hp printers.  The book was printed as a test copy and now I am comparing the printed test book copy to the screen image to see if I need to alter the image if it is far different then the test book copy.

 

I have some photo's still in adobe 1998 and when I convert to Srgb in photoshop cs5 and then do a soft proof with the printer's cmyk profile I see several out of gamut spots.  I can sometimes fix

that problem with lowering saturation in a H&S adjustment if it doesn't affect the overall color of the image.

 

**Accidently, I took a adobe 1998 profile image and converted it to CS5 working cmyk us web coated in photoshop and when I did a soft proof against the printers cmykprofile  I saw no out of gamut spots.  I then

converted the image to srgb and did a soft proof with the printers cmyk profile and again I saw no out of game spots. 

 

This printer of the book  will not be looking at the profile in the images but we are told to use Srgb and soft proof with the printers cmyk profile.

 

I do not see any difference in color when I do the conversion **(above note).  Currently I am using spyder 3 version 4 and I have set my monitor to 5800 with dim lighting and gamma 2.2 per the spdyer instructions

when color is critical.  These images are of paintings and I do see often - the out of gamut when I convert from adobe 1998 to CS5 srgb. 

 

Am I harming the overall color by doing the** above ?  Should I stay with assigning versus conversion?

 

Thanks

Ballina

 
Replies
  • Currently Being Moderated
    Dec 1, 2011 7:48 AM   in reply to ballina@earthlink.net

    Am I harming the overall color by doing the** above ?

    Yes, conversions can be considered as detrimental to image quality therefore one should keep the number of conversions to a minimum.

    Edit: Well, actually the »overall color« may be harmed less than other aspects of the image like gradients and details.

     

    By converting to a CMYK-space intermediately you most probably simply clip (or distort) the color regions that would be out of gamut for the final space, too.

     
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    Dec 1, 2011 8:00 AM   in reply to c.pfaffenbichler

    I would recommend a test:

    Convert a copy of the original Adobe RGB image to the target profile, then convert another copy as you describe and superimpose them to be able to compare them as a whole and channel by channel.

     
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  • Currently Being Moderated
    Dec 1, 2011 8:07 AM   in reply to ballina@earthlink.net

    ballina@earthlink.net wrote:

     

    ....  The printer has given me a cmyk profile for their hp printers. ...

     

    ...  we are told to use Srgb and soft proof with the printers cmyk profile ...

    What color space they want the final image? In the color space of the printer or sRGB? If they want it in the color space of the printer, it really doesn't matter what color space you are using when soft proofing with the printer's color space. Probably they told you sRGB because it is most popular. And working on a wider color space makes sense only if you are going to use the image for other destination with wider gamut than the printer.

     
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    Dec 1, 2011 12:08 PM   in reply to ballina@earthlink.net

    I assume they want sRGB to fend off customer complaints. sRGB is such a small color space that further conversion to the target CMYK will not result in much additional clipping.

     

    Try to think in terms of color spaces, then it will be easier to visualize. Small spaces, like sRGB or Web Coated SWOP, will fit entirely within a larger space like Adobe RGB. The other way around, however, will result in clipping. Once clipped, those colors don't come back.

    The profile that was changed from Adobe to SRGB was slightly lighter by pixel count

    Profile conversions change the read-out values; that's the whole point. Values change in order to keep the same color visually.

      when I went back to SRGB conversion and did a soft proof gamut warning nothing showed

    Because the colors were already clipped in the previous conversion.

     
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  • Currently Being Moderated
    Dec 1, 2011 2:47 PM   in reply to ballina@earthlink.net

    ballina@earthlink.net wrote:

     

     

    **Accidently, I took a adobe 1998 profile image and converted it to CS5 working cmyk us web coated in photoshop and when I did a soft proof against the printers cmykprofile  I saw no out of gamut spots.  I then converted the image to srgb and did a soft proof with the printers cmyk profile and again I saw no out of game spots. 

     

    This would be expected...once you do a conversion from ARGB>CMYK, all the resulting colors of the CMYK would be withing the gamut of the CMYK profile. Taking a CMYK and going to sRGB would not drive any of the CMYK colors out of the CMYK profile unless you did some color correction while in sRGB. Again this is as expected...

     

    In point of fact, this is a method I use when going from ProPhoto RGB to CMYK then from CMYK to sRGB for when clients want CMYK & RGB files. Once you've done the initial ARGB>CMYK conversion, you basically lock the color gamut to that of the CMYK profile. Since the printer is requesting sRGB images, you might want to consider the aRGB>CMYK>sRGB workflow. This will result in different colors than if you do an ARGB>sRGB conversion since a transform of an RGB to RGB profile will result in a single Relative Colorimetric rendering intent. Going from ARGB>CMYK you can use either RelCol or optionally use Perceptual as a rendering intent. Softproofing using the CMYK profile will aid in getting the best conversion. Although, you should be more concerned about the appearance of the resulting CMYK conversion not as concerned about getting all the colors into gamut. CMYK is such a small color space that the gamut warning may show a lot of colors out of gamut but it doesn't tell you what those colors will look like. That's what softproofing gives you.

     
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  • Currently Being Moderated
    Dec 1, 2011 8:16 PM   in reply to ballina@earthlink.net

    As mentioned - multiple conversions are going to be harmful.

     

    Just convert AdobeRGB (or whatever the document is already in) to the final printer profile.

     
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