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Working With Channels


Applying One Channel  Another Channel

Actually here we will swap two channels.  This will work in any color space but in this exercise we will stick with RGB.
Note:  Color channels are viewed by default in color even though they are actually monochrome.  To view channels open preferences and in "Interface" box unclick "Show Channels in Color"
  1. Open an image in RGB.
  2. Select one channel (say the blue channel)
  3. Right click on that channel and select "Duplicate Channel"  Name that channel -- the default name "blue copy" is OK.
  4. With the same (blue) channel selected use the command "Image -- Apply Image" to bring up the Apply Image dialog box.
  5. Change the blending mode to normal.
  6. Choose the channel as "Red" in the drop down menu.
  7. Click OK.  We have now replaced the Blue Channel with what was the Red channel.
  8. Now select the Red channel.
  9. Use the command "Image -- Apply Image" to bring up the Apply Image dialog box.
  10. Change the blending mode to normal.
  11. Choose the channel as "Blue Copy" in the drop down menu.
  12. Click OK.  We have now replaced the Red Channel with the duplicate blue channel and have swapped the Red and Blue channels and obtained a false color image.
We will now switch out image to the LAB color space and demonstrate that we can apply the RGB channel to a LAB channel.
  1. Change the mode of the image to LAB.
  2. Note in the channels pallette the "Blue Copy" channel is still there.
  3. Make the Lightness channel active.
  4. Use the command "Image -- Apply Image" to bring up the Apply Image dialog box.
  5. Change the blending mode to normal.
  6. Choose the channel as "Blue Copy" in the drop down menu.  Click OK.
  7. We have now made the luminosity of the image the RGB blue channel.


  1. Open an image
  2. Create a layer with a layer mask.  Either an adjustment layer which has an automatic layer mask or a duplicate layer with an added layer mask.
  3. With the layer mask selected go to Image - Apply Image
  4. Select one of the channels available -- either a regular channel or an alpha channel. 
  5. Set the blending mode to normal.  Click OK.

  6. Select the layer mask.
  7. With Image - Adjustments - Curves bring up the curves dialog box.
  8. You may now make adjustments to the layer mask -- add contrast, etc.

  9. You probably should blur a layer mask that was created from a channel.  It will normally add depth to your image.