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Ivan Zajats
Ivan Zajats
Inspiring
March 23, 2022
Answered

RGB channels issue

  • March 23, 2022
  • 3 replies
  • 2756 views

Hello! 

I've compared 3 methods of making separate layers from RGB channels.

1st: go to the Channels panel, click the channel, Ctrl+A, Ctrl+C and Ctrl+V in the Layers panel.

2nd: via the "Image - Apply image" command.

3rd: creating a Channel Mixer adj. layer (Monochrome, Red 100, Green 0, Blue 0 - for the Red channel, etc.).

 

Then I've compared the results. 2 & 3 look identical.

"Manual" copies of the channels in method 1 look slightly lighter. I can't understand WHY?!

 

Don't ask for any screenshots, because the difference is really slight and can be noticed by turning the visibility of the layers on & off. But I'm still curious why it's happening. Is it a bug or am I doing smth wrong? (hm, what can be done wrong in a simple copy-paste?)

This topic has been closed for replies.
Correct answer c.pfaffenbichler
@Ivan Zajats wrote:

Now let's find out why the copy-paste of any channel to a separate layer looks lighter than created via the "Image - Apply image" or the Channel Mixer. Wrong settings or a Photoshop's bug? Someone mentions the color space, on Facebook I was told about the Gamma (nothing concrete) and color settings as well.

Try pasting the copied R-Channel into each of the three Channels of a white Layer. 

That way the copied grayscale pixel content is not converted to RGB and thus the gamma-correction does not apply. 

 

Or set the Grayscale Working Space to a Gamma corresponding to the RGB Space of the image – but remember you may want to reset it afterwards, especially if you actually work on grayscale images for print at times. 

3 replies

Ivan Zajats
Ivan ZajatsAuthor
Inspiring
March 24, 2022

Now let's find out why the copy-paste of any channel to a separate layer looks lighter than created via the "Image - Apply image" or the Channel Mixer. Wrong settings or a Photoshop's bug? Someone mentions the color space, on Facebook I was told about the Gamma (nothing concrete) and color settings as well.

c.pfaffenbichler
Community Expert
c.pfaffenbichlerCommunity ExpertCorrect answer
Community Expert
March 24, 2022
@Ivan Zajats wrote:

Now let's find out why the copy-paste of any channel to a separate layer looks lighter than created via the "Image - Apply image" or the Channel Mixer. Wrong settings or a Photoshop's bug? Someone mentions the color space, on Facebook I was told about the Gamma (nothing concrete) and color settings as well.

Try pasting the copied R-Channel into each of the three Channels of a white Layer. 

That way the copied grayscale pixel content is not converted to RGB and thus the gamma-correction does not apply. 

 

Or set the Grayscale Working Space to a Gamma corresponding to the RGB Space of the image – but remember you may want to reset it afterwards, especially if you actually work on grayscale images for print at times. 

    Ivan Zajats
    Ivan ZajatsAuthor
    Inspiring
    March 24, 2022

    Brilliant! it works! I copied the Red channel to a blank layer and then to each channel of that layer.

    The composite RGB channel became a bit darker than any of the channels separately (though they are identical). And now it equals the results of two other methods. Great! Thanks!

     

    Now I'm going to record an action (for masking purposes).

    The "Image - Apply image" command seems to be the easiest option of all those 🙂 

    But I just wanted to study all of them.

    c.pfaffenbichler
    Community Expert
    c.pfaffenbichlerCommunity Expert
    Community Expert
    March 23, 2022

    What are you trying to achieve with this? 

    And would three instances of one Smart Object with Advanced Blending limited to one Channel each not suffice? 

     

    »1st: go to the Channels panel, click the channel, Ctrl+A, Ctrl+C and Ctrl+V in the Layers panel.«

    Your description seems to be missing something; a grayscale image pasted into an RGB image would be white-to-black on all three Channels.  (but depending on the Color Spaces the three resulting Channels would differ from the originally copied Channel) 

      Ivan Zajats
      Ivan ZajatsAuthor
      Inspiring
      March 23, 2022
      quote

      What are you trying to achieve with this? 

      With what? channels? I've mentioned in the second post, be attentive 🙂

       

      quote

      And would three instances of one Smart Object with Advanced Blending limited to one Channel each not suffice? 

      Sounds complicated, expand the idea, I don't understand.

      c.pfaffenbichler
      Community Expert
      c.pfaffenbichlerCommunity Expert
      Community Expert
      March 23, 2022

      I guess I had misunderstood what you want to achieve, so this particular SO approach would be no use to you. 

       

      As for method 1 I already mentioned that the result for pasting a grayscale image in an RGB image  depends on the Color Spaces. 

      Please post meaningful screenshots for method 2 and 3 including all pertinent Panels. 

      For method 3: What are the complete settings of the three Adjustment Layers? 

      You know that an Adjustment Layer works on the basis of the result for the whole stack below it? 

       

      I recommend trying not to mention what you are actually talking about only in the second post in the future. 

        Ivan Zajats
        Ivan ZajatsAuthor
        Inspiring
        March 23, 2022

        Another strange issue: as I've said, Apply image & Channel Mixer results look identical.

        BUT! If I change the Blend mode of the layers to Linear Burn (for masking purpose) and compare both groups, the Channel Mixer group looks lighter. Magic...

         

        Apply image group

        Channel Mixer group

         

        The layer structure: layers with the arrows are in the Linear Burn blend mode.

         

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