How do I apply an adjustment layer to an alpha channel

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Aug 10, 2007
I am using Photoshop CS2 on a Windows XP SP2 platform. I am working in RGB using the Adobe RGB (1998) color space.

I’ve been reading the book, "Real World Image Sharpening with Adobe Photoshop CS2" by Bruce Fraser. (The book is excellent by the way!)

One of the things the book discusses is creating a selection mask (by using Image > Calculations) and using it as a layer mask to constrain sharpening or reduce noise filters applied to that layer.

After he creates a mask (saved as an alpha channel) he clearly shows applying a Levels adjustment and a Curves adjustment to an alpha channel. For example, on page 180, he shows a screen shot (Figure 5-17) where a Curves dialog shows "Alpha 1" in the Channel drop down. And, on page 186, he shows a screen shot (Figure 5-25) where a Levels dialog shows "Alpha 2" in the Channel drop down.

Does anyone know how to do this? I can’t seem to get the alpha channels to appear in the drop down menus for either Levels or Curves.

Thank you in advance for your advice, tips, comments, and suggestions!


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Aug 10, 2007
You can’t apply an Adjustment Layer to an Alpha Channel. You have to adjust the channel directly, via Image > Adjustments > Levels (Ctrl+L) or Image > Adjustments > Curves (Ctrl+M).
Aug 10, 2007
John –

Thank you so much!

I was trying to have the alpha channel showing in my screen, and then use the "yin-yang" "Create a new fill or adjustment layer" icon at the bottom of the Layers tab on the Layers palette.

I can’t believe the answer is as simple as stay on the Channels tab of the Layers palette, select the channel, and then go to Image > Adjustments > Levels or Image > Adjustments > Curves.



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