9 Replies Latest reply on May 2, 2009 8:18 PM by npeqp

    Critique on Photoshop's Desaturate Implementation

    npeqp

      http://en.wikipedia.org/wiki/Saturation_(color_theory)

       

      See; 'CIELAB lightness preserved, with a* and b* stripped, to make a grayscale image.'

       

      I'm surprised to find that Adobe has implemented an averaging function for the desaturation feature. That method has the artifact of destroying the lightness of color components in an image, I would appreciate it if Adobe assumed that when the user wants to desaturate an image they specifically mean of color, not both color and defecting lightness.

       

      In searching Google I have not found that this issue has ever been raised (as far as my results go), and I raise critique on this forum hoping the right people understand that it can clearly be argued Photoshop's desaturation function does not give correct results.

       

      In case anyone suggests simply lightening up the image after performing Photoshop's desaturation function; I respond that this not a true solution to the problem, it's far too imprecise. Software I have written to implement a proper desaturation function (based on the wiki above) have given different, and much better, results than any vague and loose best-guess attempt to correct the image within Photoshop itself.

       

      Aside that, in my experience in implementing this so far I can clearly state that this should be a trivial and basic function which should be a part of the proclaimed industry standard image manipulation software.

       

      Later this weekend I will host a script and refer to it here which properly desaturates an image without affecting the V component in the HSV color space.

       

      Thanks for hearing my criticism, if you feel I've been vague ask me any specific questions to clarify -

       

       

      : ]

        • 1. Re: Critique on Photoshop's Desaturate Implementation
          Zeno Bokor Level 6

          why don't you use the Black & White adjustment layer for this and decrease the opacity of the adjustment layer if you want to reduce it's effect

          • 2. Re: Critique on Photoshop's Desaturate Implementation
            John Joslin Level 6

            why don't you use the Black & White adjustment layer for this and decrease the opacity of the adjustment layer if you want to reduce it's effect

             

            ... or do it in Adobe Camera Raw.


            I think they stopped developing the simple desaturate tool with so many alternative methods available.


            Photoshop is full of legacy functions which they daren't remove for fear of offending someone. 

            • 3. Re: Critique on Photoshop's Desaturate Implementation
              npeqp Level 1

              It seems to me you may be confused, as I stated the feature should not force users to artifically affect lightness - the feature should *maintain the V component in the HSV color space of an image as it exists originally and only affect, precisely, the Saturation of Hue.

               

              A proper solution for desaturation is actually useful. The task to artificially manipulate lightness should only apply *if desired, Adobe's implementation should not assume the client wishes to modify the V component in the HSV color space when attempting to desaturate, it is wrong to assume anything. Professionals should have the confidence that they have specific and exact control over their images various color space components.

               

              People who don't care now won't care after the change, it's a win-win modification since it strictly enhances the precision of the function which would elude those who don't pay attention to it to begin with.

              • 4. Re: Critique on Photoshop's Desaturate Implementation
                npeqp Level 1

                Notice the differences, in the context of the HSV color space:

                 

                - the lightness has been preserved;

                http://luniac.com/~simpleid/vfx/HSV_Intact.bmp

                 

                - the lightness has been modified by PhotoShop;

                http://luniac.com/~simpleid/vfx/PhotoShop.bmp

                 

                Original image, and details of saturation; http://en.wikipedia.org/wiki/Saturation_(color_theory)

                • 5. Re: Critique on Photoshop's Desaturate Implementation
                  Zeno Bokor Level 6
                  People who don't care now won't care after the change, it's a win-win modification since it strictly enhances the precision of the function which would elude those who don't pay attention to it to begin with.

                  ok, so then, will you flip the switch that magically enables this feature or will you let me do it? If all you want is the L channel then go to Image->Mode->Lab Color, go into the Channels panel, select the L channel and then go to Image->Mode->Grayscale. Too much of a hassle? then make an action that does this for you

                  • 6. Re: Critique on Photoshop's Desaturate Implementation
                    npeqp Level 1

                    That does work correctly, which is great. And no, it's not difficult to do that, but maybe you're not really understanding my point..

                     

                    If it says it will do something, it should do just that, regardless if there's some other obscure way to achieve the desired results, that's just poor UI design.

                     

                    However, the function desaturate produces artifacts (by the reasoning above, I'm all ears for an arguement against the views I've presented), I'm just wondering if it has or will be addressed.

                     

                    It's just in my nature to achieve and desire proper and precise implementation of software features, maybe I'm just crazy though, but I thought Adobe engineers may feel similiarly and might have looked over a few things unintentionally.

                     

                    So I hope people might more clearly understand now what I'm trying to discuss.

                    • 7. Re: Critique on Photoshop's Desaturate Implementation
                      Zeno Bokor Level 6

                      the problem with your request is that you are asking an image in RGB color mode to do Lab color math, not something easily acomplished. Note that with my method you have to merge everything down before going to Lab otherwise you will most likely get color shifts

                      • 8. Re: Critique on Photoshop's Desaturate Implementation
                        Level 7

                        HSL, HSV, HSB, HCV, Lab -- all have a Lightness, Value or Brightness components, and all can be desaturated by nulling 2 channels.

                        But each one will get a different result.

                         

                        Photoshop's method is completely valid, and gives correct results -- it is just not the exact method that you prefer.  Most likely because you do not understand which color model is being used, or the goal of the command.

                         

                        Please spend some time to learn more about the color models and terminology being used.  If you know more about it, you'll find that Photoshop is offering you both convenience and a lot of power and flexibility.

                         

                         

                         

                         

                        BOOT NOTE - LCH would give the same result as Lab, because the CH channels are just transforms of the ab channels (which get nulled to give the grayscale image).

                        • 9. Re: Critique on Photoshop's Desaturate Implementation
                          npeqp Level 1

                          Thank you for your response Chris, I see now my reasoning was entirely from the perspective of what I assumed should be intuitive, but understanding now that all math is done intentionally relative to the current color space, without transformations between color spaces, makes sense to explain the results I see. It just seemed unintuitive to see PhotoShop tell me I was modifying the saturation of the color and see lightness be affected.

                           

                          Sorry for misunderstanding, but thank you, I should have realized that. :-]