7 Replies Latest reply on Apr 28, 2009 10:38 AM by Lou Dina

    How to disable grayscale shift?

    ZZAABB

      For now i need to convert an RGB (16 bit per channel, but actually grayscale, r=g=b) image to 16 bit grayscale image... Strange color settings in Photoshop always produce a color shift and resulted image looks different from original one. Which combinations of color profiles for rgb and grayscale i shold use to produce the SAME images without any gamma/color shift?

        • 1. Re: How to disable grayscale shift?
          Lou Dina Level 3

          ZZAABB,

           

          I cannot replicate your problem, no matter what I do.  I tried numerous gamma and dot gain grayscale spaces, and they all looked identical to the original image.  When you "Convert" from one space to another, the files should look pretty much identical (as long as all your tones and/or colors are within the destination space's gamut).  Numbers in the file itself will change, of course.  You aren't "assigning" a profile, by any chance, are you?

           

          Tell us specifically your beginning RGB color space, your destination grayscale space, and the steps you are using to get there.  And, are you sure your entire original image was totally neutral throughout (r=g=b)?  If you had any toning, even in parts of the image, they would end up being pure gray in your grayscale image.

           

          In general, if your intent is display on a monitor, gamma 2.2 (or sometimes gamma 1.8) is a good grayscale space.  You can also use them as source spaces for output to an inkjet.  If you are sending a job to a press, you normally want to use a dot gain space, or better yet, a custom profile.

           

          Lou

          • 2. Re: How to disable grayscale shift?
            ZZAABB Level 1

            heh its my fault i forgot to say thet this problem is photoshop alone... when you are using same grayscale color profile you can save and open image without any noticable color shift but if you are open this grayscale 16bit tiff in acdsee for example you will see the difference with original 16 bit RGB image also you will see it if you are open grayscale image wich was saved with different grayscale color profile in photoshop...

             

            when you are openning rgb image photoshop apply rgb profile to it, then you can convert it to gray without any noticable changes in photoshop view, then when you are saving it photoshop apply reverse grayscale profile to the image and saves it to tiff file... when you are trying to open it photoshop apply profile and show you the image wich looks like orogonal one in photoshop but it isnt, if you are open original rgb and grayscale images in acdsee you will see the difference in color intencity

            • 3. Re: How to disable grayscale shift?
              Lou Dina Level 3

              ZZAABB,

               

              I am having some difficulty understanding your explanation, and assume English is not your native language.

               

              First, it is good to know that your image looks the same when converting a neutral RGB image to grayscale in Photoshop. When you save the new file, be sure to save it with an embedded profile, other color managed applications recognize and apply the proper profile for viewing, editing and printing.  Some programs do not recognize color tags, and even some color managed programs are not able to process grayscale, CMYK, Lab or files that are not RGB (or at least, process them accurately).  I don't use acdsee, so cannot comment on it.  It is possible that even if acdsee and similar programs do process these files, they may be using a different color management engine for conversion, though I would expect any differences in this case to be minor.

               

              If it looks the same in Photoshop when converting, then I'd say your other program is not able to handle the grayscale files.  Does your original neutral RGB file look the same in acdsee as it does in Photoshop?  If so, then I suspect acdsee is having trouble with grayscale or CMYK files.

               

              Lou

              • 4. Re: How to disable grayscale shift?
                ZZAABB Level 1

                I know that photoshop trying to save color profile to grayscale tiff file and many other programs wont read it (even acd see) and my question is exactly how to disable this strange behavior i wanated to save the same 16 bit integers for grayscale channel from original one rgb image without any strange shift and profiles... for now i solved this problem using grayscale 16 bit png files, which could be opened and saved in photoshop without noticeable changes cause photoshop use the same grayscale profile during open and save operation... but issue with different profiles for rgb and grayscale are open!

                • 5. Re: How to disable grayscale shift?
                  Lou Dina Level 3

                  You can save your original "neutral" RGB file with or without a profile.  Or, you can convert to grayscale and save with or without a profile.  You can save as TIFF, JPG, or whatever file format you want.  If ACDSEE cannot handle one option, then try another.  If it chokes on color managed files, then the problem is with acdsee, not Photoshop.  Many browsers are not color managed either, so you just have to work around it, but that is an issue with the browser, not Photoshop.

                   

                  Why do you want to convert to grayscale?  Why not just leave it as a neutral RGB image?

                   

                  BTW, Photoshop can use the same profile to open and save a file with an ICC profile in any format that accepts color tags.  Check the Photoshop color settings in your preferences to be sure they are set properly.  Maybe you have it set to do unwanted conversions.

                   

                  Lou

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                  • 6. Re: How to disable grayscale shift?
                    ZZAABB Level 1

                    using external ICC profile sound good but they have different format grayscale icc wont work for rgb... and color profiling is a good feature but why there is no option in photoshop which disables this profiling or at least make it linear as i wanted?

                    • 7. Re: How to disable grayscale shift?
                      Lou Dina Level 3

                      ZZAABB,

                       

                      I think we have a bit of a language barrier, but I really don't know what you are talking about.  But, I will try to respond anyway, hoping that I answer your questions.

                       

                      RGB profiles can only be assigned to RGB files, grayscale profiles can only be assigned to grayscale files, CMYK profiles can only be assigned to CMYK files, etc.  You can convert from RGB to grayscale or CMYK, grayscale to RGB or CMYK, or from CMYK to grayscale or RGB, but then your file is in the new color mode.  You don't need a grayscale file in order to display a perfectly neutral RGB file, as long as R=G=B throughout the tonal scale.

                       

                      I have no idea what it is you are trying to accomplish.  If you are talking about a non-standard grayscale profile that is not recognized as a standard ICC profile, then you will have to address that in some other way.

                       

                      Photoshop ALWAYS has color management operating at some level.  It ALWAYS adjusts the file for display on your monitor (unless you set the proof to Monitor RGB, which passes the numbers straight through to your monitor without modification).  And if your Photoshop color settings are set to Adobe RGB for your standard RGB color space, then if you bring a file into Photoshop without a color profile, (or choose to not color manage the file), then it will be "assumed" to be Adobe RGB, and colors will be displayed on that basis.  The same is true of grayscale and CMYK files.

                       

                      The only way to get consistent, accurate display or tone and color in Photoshop is to have a properly calibrated and profiled monitor, and to make sure your files are properly tagged.  Then, you need to make sure Photoshop recognized and honors that tag.

                       

                      I think I have said as much as I can say at this point.  You will either have to explain your problem MUCH more clearly, so we can really understand what you are trying to do and exactly what you are doing at the current time, otherwise I will make this my last post on the subject.  Best of luck.

                       

                      Lou