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_Aykut_Kaplan_
Participant
September 21, 2007
質問

Best results when changing RGB to CMYK

  • September 21, 2007
  • 返信数 13.
  • 524711 ビュー
Hi There,

How can I get the best results when converting a RGB to CMYK? For example, a tif visual when offset printing... Is there any programme, plug in, machine for this?

Many thanks
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      _cliffinmi_
      Participant
      December 20, 2007
      I agree with Marco U.

      I might have said: only use Perceptual if an extremely important color in a photo changes terribly using Relative Colorimetric -- otherwise use that. The reason: The former method can make the whole picture shift (usually yellower and weaker) but the latter can make several distinctly different colors (like 3-5 different reds for example) and make them the same. Usually, one or two really strong colors can get shifted somewhat, but won't be noticeable in an otherwise great looking image.

      The secret to converting for good print color is to choose the source and target correctly.

      If you are serious about color, buy the book "Real World Color Management" by Bruce Fraser, Chris Murphy and Fred Bunting.

      http://www.amazon.com/Real-World-Color-Management-2nd/dp/0321267222/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1198178251&sr=1-1

      Sadly, Bruce Fraser passed away, so the book may not go to a third edition.But you can still get the second edition and the first 5 or 6 chapters are an education in themselves.
        A
        Anonymous
        October 16, 2007
        To convert an RGB file to a target CMYK space, open the image file in Photoshop, then go to Edit > Convert to Profile.

        Once there, select your target profile (a copy of which should be in the [Your Computer] > Library > ColorSync > Profiles folder, or else it will not appear in the pulldown menu).

        Then select a rendering intent appropriate for your image (to simplify, Perceptual if the relevant image colors are out of the target's gamut, otherwise Relative Colorimetric). If you select Relative Colorimetric, it's also a good idea to check "Use Black Point Compensation".

        Do NOT use the Image > Mode > CMYK command to convert your image, because that does not offer the degree of control that you have with Convert to Profile, and limits you instead to the target space and conversion controls set in the application's Color Settings, which may not be appropriate for your purposes.

        There's more to all of this, of course, but that would be a good start.
          P
          pullela kartik
          Known Participant
          March 20, 2017

          Hello Macro,

          I really need this question answered in a more simplified way.

          I believe the solution/answer you provided was the right action to get the job done. But, I did not understand.

          I am not a big expert of the color subject and not a technical expert. But I am in need for this.

          I created a logo for a client in photoshop using RGB profile. Client approved the design and colors. And wanted me to provide the design in CMYK as well.

          In the past, for the same purpose in photoshop, I used to open a new file with CMYK profile and drag the logo layers from RGB file to CMYK file. And publish the file into desired formats.

          Was that a correct approach?

          Pls let me understand the best way to do the needful. Thanks.

          regards

          Kartik

          P
          Printrix
          Known Participant
          March 23, 2017

          If the colors chosen in RGB don't convert properly to CMYK they are probably out-of-gamut for your CMYK profile. Adobe RGB1998 has a gamut volume of 1,207,520 vs 402,102 for Fogra39 and 296,515 for US Web Coated v2. In other words 2/3rd of the colors available in Adobe RGB1998 are not (as in never) available in Fogra39 or US Web Coated v2. The best possible solution you can get is to convert using the "convert to profile" option in the Edit menu and play around with the rendering intents. I think you will get the best result with Relative Colorimetric with Black Point Compensation enabled. Another option (in my opinion the best) is to explain your customer that web colors (viewed on a monitor) are (and generally should be) more saturated than printed colors (business cards, documents, etc. printed on offset press). The average consumer eye adapts anyway to the color difference between the two. You rather have a saturated logo on a webpage and the closest match on print than a match between web and print as the logo on web would look very dull in the latter.

          If you drag and drop a design from Photoshop to Illustrator the color will be converted to the color profile active in Illustrator (Menu -> Edit -> Colorsettings). I always prepare the designs with the same color settings in both Photoshop and Illustrator before drag&drop or place (Menu -> File -> Place).

          Always to choose an adequate working space before creating your designs, it will prevent such issues. There are predefined settings depending on your region and application. You will have to switch very often between two of them, one for web and one for print. They're pretty self-explanatory:

          North America Web/Internet or Europe Web/Internet 2

          North America Prepress 2 or Europe Prepress 3

          There a a few others like newsprint and general purpose but I never need/use them.

          I advise to set the appropriate color settings before creating the new design.

          Remarks:

          - Whenever I convert between profiles I always play around with the rendering intents while the "preview" is enabled. This allows to quickly evaluate for the best conversion setting.

          - Never include the sRGB profile for web applications in your files (option available after pressing "save as")! In Firefox you can enable colormanagement and logo's and pictures will look very dull on the screen of the user.

          Regards,

          Steven

            LucienSchilling
            LucienSchilling
            Known Participant
            October 16, 2007
            Photoshop - Illustrator - InDesign and respect your colour profiles (sRGB <> AdobeRGB etc).

            Lucien.
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