4 Replies Latest reply on Feb 5, 2014 7:55 AM by victorhrdp

    Diferences between RGB and CMYK with the same color.

    victorhrdp

      Hello.

       

      I'm trying to understand color management in Photoshop. But in some cases I am lost.

       

      In color settings:

       

       

      I make a new RGB and CMYK document and I put the same color in CMYK:

       

      C = 100%

      M = 0%

      Y = 0%

      K = 0%

       

      The color in the screen is different. How is that possible?

       

      Thanks.

        • 1. Re: Diferences between RGB and CMYK with the same color.
          D Fosse Adobe Community Professional & MVP

          First of all don't use Monitor RGB. That's your monitor profile, which Photoshop uses behind the scenes to display the file correctly on screen. The working space / document profile should always be a standard color space such as sRGB, Adobe RGB (or ProPhoto; but that's only if you know what you're doing). I'd recommend you stick with sRGB for now.

           

          Document profile and monitor profile are two different things, serving different purposes. Don't mix them up.

           

          So try again with sRGB and ISOnewspaper. Still different? Then it's because the color is out of gamut in one of them. It simply can't be contained in that color space, so the conversion ends up with the closest possible match. Pure cyan, which is what you have, is a primary color in CMYK. But in RGB it's midway between the blue and green primaries. Think of it as two triangles overlaid, but one turned 60 degrees.

          1 person found this helpful
          • 2. Re: Diferences between RGB and CMYK with the same color.
            victorhrdp Level 1

            Thanks for your quick answer.

             

            I´ve tried a proof with the sRGB profile and the results are similar.

             

            These are my color options:

             

            Opciones.jpg

             

            I´ve made two new documents, CMYK and RGB.

             

            I´ve selected a pure Cian color and I´ve put it on the document.

             

            The two colors aparently are in gamma. No yellow triangles, etc.

             

            The resulting colors on screen are different.

             

            I´m very rookie in color management but I think the color in the screen must be the same. Am I right?

             

            For example, If I use "CoatedFogra27" profile in the same enviroment, the result CMYK and RGB documents show the same color on screen.

             

            Thanks for your attention.

            • 3. Re: Diferences between RGB and CMYK with the same color.
              D Fosse Adobe Community Professional & MVP

              Working spaces are OK, but you also need to go down to Color Management Policies. For RGB you currently have "off" (desactivar). This is a setting you should never use, it'll get you into big trouble, fast. It's only there for very special purposes. For CMYK you have "convert to working space" which is not quite as bad, but also very risky.

               

              Set both to "Preserve Embedded Profiles". This is the safe route. It's also a good idea to check all the three warnings, so that you know when you have missing profiles or mismatches.

               

              So try again with that setup. It is still perfectly possible that your pure cyan is out of sRGB gamut, it simply can't be reproduced in that color space because it's too saturated. So what you see is the most saturated cyan possible in sRGB. Primary colors in either RGB or CMYK are always difficult in the other mode.

               

              Try with more muted colors first.

              • 4. Re: Diferences between RGB and CMYK with the same color.
                victorhrdp Level 1

                Thanks for your reply.

                 

                I used the configuration than you propose and the result has differences in color between CMYK and RGB. But the RGB is out of gamma.

                 

                On this point I have several questions. And a terrible headache.

                 

                I used for testing a motor color (Little Cms) and the results for RGB are the same as for the RGB document in Photoshop. This motor has a calculator.

                 

                The operation is here:

                 

                IsoNewsPaper26v4 -> Calibrated Monitor = The Cian color appears equal in screen and RGB values from motor color.

                 

                I use this conversion because pure Cian converts to Lab, reconverts to RGB and shows in Calibrated monitor.

                RGB.jpg

                This is the CMYK version:

                 

                CMYK.jpg

                I used this operation:

                 

                IsoNewsPaper26v4 -> sRGB = The Cian color is different between screen and value RGB from color motor.

                 

                I tried with others (AdobeRGB, Pro Photo, Monitor, etc). I can´t obtain the color showed in PhotoShop.

                 

                In CMYK, what is the sequence of color profiles used to obtain this difference in color?

                 

                Thanks.