6 Replies Latest reply on Sep 10, 2007 10:34 AM by Sami@Adobe

    about color theory

    be-sign.net
      hi,
      my question is about some theory. if i am wrong in this forum, please tell me, where i will be right.
      my question: the last days i looked about conversation colors from rgb to hsv, rgb to cmyk and rgb to cielab. i found some formulas, and used them in a script (filemaker). i found, that my results are identical with the results of some other color-conversation tools. but my resluts are differing from the results in kuler and in photoshop.
      i suppose, that the reason for the differences in photoshop are color-profiles. but where are the differences to kuler? is kuler using any profiles? use kuler another formular? how does kuler work (or is this knowledge confidential)?
      thanks for any answers.
      regards bernd scheurer
        • 1. Re: about color theory
          tLindroth
          My question is, why do you do these conversions? Since RGB and CMYK are one set of color spaces and HSV and CIELAB another. RGB and CMYK are device specifik. 134.255.122 one my computer will will not be the same color on yours. The same goes for CMYK, it differs between offsets. CIELAB on the other hand should be general but there are different interpretations of CIELAB so with different implementations you will get different results.

          But why do you do these conversions? If you want to be sure that a color, lets say Adobe red, is truly adobe red, then you have to use a color space that is defined by colors and not numbers i.e Pantone. Or you have to use a truely magnificient "device", your own eyes. You may also use a colormeter, but your eyes will do. If you want to ensure that colors stays the same, this is the easiest and most reliable way. The other way is to produce ICC-profils for each of your devices and in that way calibrate your color process, from scanner and camera to monitor and printer. If you work for a monthly magazin for fashion clothing, this is the way to go. But calibrating your monitor is always a good thing. Try the "ColorVision Spyder 2 Express" for a not to expensive solution.

          //T

          • 2. Re: about color theory
            tLindroth Level 1
            My question is, why do you do these conversions? Since RGB and CMYK are one set of color spaces and HSV and CIELAB another. RGB and CMYK are device specifik. 134.255.122 one my computer will will not be the same color on yours. The same goes for CMYK, it differs between offsets. CIELAB on the other hand should be general but there are different interpretations of CIELAB so with different implementations you will get different results.

            But why do you do these conversions? If you want to be sure that a color, lets say Adobe red, is truly adobe red, then you have to use a color space that is defined by colors and not numbers i.e Pantone. Or you have to use a truely magnificient "device", your own eyes. You may also use a colormeter, but your eyes will do. If you want to ensure that colors stays the same, this is the easiest and most reliable way. The other way is to produce ICC-profils for each of your devices and in that way calibrate your color process, from scanner and camera to monitor and printer. If you work for a monthly magazin for fashion clothing, this is the way to go. But calibrating your monitor is always a good thing. Try the "ColorVision Spyder 2 Express" for a not to expensive solution.

            //T

            • 3. Re: about color theory
              be-sign.net Level 1
              hi,
              and thanks for reply. i know, that colorspaces are device specific. but i see, for example that kuler will convert a rgb-color in a different cmyk-color than photoshop. so, what sense make the conversion of color-spaces in kuler, if the result is not compatible with other /my devices?

              i do this conversions, because i collect some colors about my projects in one module of my filemaker database. i can input the rgb-datas in specific fields (and display the result as a rgb-colored box). other databasefields calculate the conversions to cmyk, cielab, ect. so i have all color-informations, i need for my work. thats the theory.
              but i see also, that kuler gets other results as photoshop, who gets other resluts as ....

              is it right, that the missing link in my (or kulers) conversion is the icc-profile, photoshop is using? if yes: whats the right way to use a profile in a conversion? or: what kind of conversion-result is the kuler-cmyk without my profile? can i named it as a "theory-only and profile-fee" native-cmyk?

              i hope, my english is good enough, to clarify my question.

              regards
              bernd scheurer
              • 4. Re: about color theory
                jacobrus Level 1
                As far as I can tell, Kuler has no way of knowing what RGB and CMYK to use for your specific needs. It probably just assumes some standard profiles, like sRGB and some SWOP space, or similar. Because Flash has no color management, the colors shown by Kuler are inherently inaccurate and will display differently on every computer (and will be wildly different on PCs and Macs). If you need accurate color conversions, Kuler is not the tool you should use.
                • 5. Re: about color theory
                  be-sign.net Level 1
                  hi jacobolus,

                  thanks for your explanations. now i understand the conversions at kuler. my conversions are also without any profiles and will be good as rough calculation.

                  regards
                  bernd scheurer
                  • 6. Re: about color theory
                    Sami@Adobe Adobe Employee
                    Thanks to Jacobolus and tLindroth for weighing in with color management wisdom.
                    Sami