7 Replies Latest reply on Sep 8, 2013 11:24 AM by TurgayOrhan

    HSL adjustment with luminosity masking

    TurgayOrhan Level 1

      Let me list my steps ...

       

      1. Duplicate the image which is in RGB mode

      2. Change the mode of the duplicated image to LAB color mode

      3. Select "lightness" channel in the duplicated image

      4. Move it into the RGB image as alpha channel

      5. Copy this channel and invert the copied channel

      6. Create two HSL adjustments with these two channels used as masks

      7. Turn off completely the saturation sliders in the HSL adjustments for desaturating the image

       

      Now, I can not get completely desaturated image after these steps ...

      Is there a leakage between my luminosity masks?

       

      Any idea ...

       

      Thanks.

        • 1. Re: HSL adjustment with luminosity masking
          Mylenium Most Valuable Participant

          Lab luminosity is not necessarily the same as calculating the luminosity from an RGB channel and this would be influenced by Gamma, color profiles and other things. You would need to actually produce the luminosity result using channel operations e.g. with Calculations or stacking duplicate layers.

           

          Mylenium

          • 2. Re: HSL adjustment with luminosity masking
            TurgayOrhan Level 1
            Lab luminosity is not necessarily the same as calculating the luminosity from an RGB channel and this would be influenced by Gamma, color profiles and other things.

             

            I tried it with the lightness channel from the HSL (derivative of RGB) color space, but I got the same result.

             

             

             

            You would need to actually produce the luminosity result using channel operations e.g. with Calculations or stacking duplicate layers.

             

            I don't have any idea how I can produce luminosity from a RGB image with the channel calculations. A web link would be greatly appreciated ... thanks.

            • 3. Re: HSL adjustment with luminosity masking
              TurgayOrhan Level 1

              When a channel with its inverted are added together, their opacities are perfectly added to each other ... all the pixels are turning to pure white (255,255,255).

              But, when a channel with its inverted are used as masks in the layer panel, their opacities are not added to each other perfectly for showing the following layer ... in my case HSL adjustment layers.

               

              Is there a solution for this case?

              • 4. Re: HSL adjustment with luminosity masking
                G.Hoffmann Level 3

                Turgay, if your intention is nothing else but image desaturation, you may use

                 

                Image Adjustment > Desaturate

                 

                or

                 

                Image > Mode > Grayscale 

                followed by

                Image > Mode > RGB Color

                 

                In Lab an image can be desaturated  by setting a=0 and b=0 simultaneously.

                This is as well a nice approach for assigning a tint (a not 0, b not 0).

                 

                HSL or HLS is not a colorimetrically correct color system.

                http://docs-hoffmann.de/hlscone03052001.pdf

                 

                Best regards --Gernot Hoffmann

                • 5. Re: HSL adjustment with luminosity masking
                  TurgayOrhan Level 1

                  Thanks Gernot ...

                   

                  HSL adjustment layer was just an example ... indeed, I want to correctly split highlights and shadows with a luminosity mask (without any leakage between the masks) for controlling different type of adjustments for different tonal regions.

                   

                  ....

                   

                  I would like to ask a question about the Lab color model to you ...

                  Can we separate saturation from the a and b channels for a saturation mask?

                  • 6. Re: HSL adjustment with luminosity masking
                    G.Hoffmann Level 3

                    Orhan,

                     

                    I would avoid HLS (HSL). This is more a kind of navigational system, an easily

                    understandable color space but much less one for calculations (therefore I had

                    used a somewhat modified approach in my doc).

                     

                    Lab is a good choice. Saturation is approximately the radius in the plane a-b,

                    (vector length from the origin to a point (a,b) ).

                     

                    For your purposes I would recommend this proceeding:

                    Image > Mode > Lab Color

                    Layer > New Adjustment Layer > Curves

                    ...modify L and eventually a,b

                    Layer Style > Blending Options

                    Here we have for each channel two sliders for top layer / bottom layer.

                    Each slider can be split by ALT+LeftMouseClick (move mouse) in order

                    to create soft transitions.

                     

                    layer-style.png

                     

                    This is a direct approach for selective corrections. With masks I'm not

                    so familiar.

                     

                    Hope this helps a little.

                     

                    Best regards -- Gernot Hoffmann

                    1 person found this helpful
                    • 7. Re: HSL adjustment with luminosity masking
                      TurgayOrhan Level 1

                      Thank you so much ...

                      Great help.

                       

                      Very nice approach for tone and color corrections.

                      I think ... I should spend much more time on this.

                       

                      Thanks again ...