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Methods for channel blending usually involve destructive methods such as Apply Image or Channel Mixer. But there is another method that is not only nondestructive, it also allows you to use the power of layers when dealing with channels. Here's how it works:
Let's say you have a dirty blue channel, and you think blending in part of the green channel might fix it.
1. Go into Channel palette. Select and copy the green channel. Go to the layer palette. Paste. Now you have the green channel's "grayscale" sitting on top of the Background layer of your image. Activate the Blending Options menu for the "grayscale" layer. Under Advanced Blending|Channels, uncheck the boxes for "R" and "G." Click okay.
2. What you see on your monitor is the image with the grayscale of the green channel substituting for the grayscale of the blue channel. And as you lower the opacity you blend in more of the blue channel and less of the green channel, until you get it to where you want it.
3. Now, maybe you want to see how the L channel works here instead. You take it from a second copy of your picture, put it in there, and set its advanced channel blending to "B" only. Now you click back and forth between the L layer and the G layer to see which one works better. And because it's too light, you add an adjustment layer, set its advanced blending to "B" only, and reduce lightness. All in a nondestructive way.
And it doesn't end there. Add the fact that you can use layer masks and blending modes. And you can use this to hand-retouch a channel without wrecking it. Just make a copy into a layer, have it feed into the original channel, and then brush away. You see the changes live, and never touch the actual channel.
The amount of flexibility this brings to channel operations is mind-boggling. But it has not been tested much. So have at it, and report back how it works for you.
BTW, I did not invent this technique. It was suggested to me during a conversation with a user named Witkacy over in the Photoshop featurerequest group. I immediately began testing this and I'm posting everywhere I participate so others can try this out.
Let's say you have a dirty blue channel, and you think blending in part of the green channel might fix it.
1. Go into Channel palette. Select and copy the green channel. Go to the layer palette. Paste. Now you have the green channel's "grayscale" sitting on top of the Background layer of your image. Activate the Blending Options menu for the "grayscale" layer. Under Advanced Blending|Channels, uncheck the boxes for "R" and "G." Click okay.
2. What you see on your monitor is the image with the grayscale of the green channel substituting for the grayscale of the blue channel. And as you lower the opacity you blend in more of the blue channel and less of the green channel, until you get it to where you want it.
3. Now, maybe you want to see how the L channel works here instead. You take it from a second copy of your picture, put it in there, and set its advanced channel blending to "B" only. Now you click back and forth between the L layer and the G layer to see which one works better. And because it's too light, you add an adjustment layer, set its advanced blending to "B" only, and reduce lightness. All in a nondestructive way.
And it doesn't end there. Add the fact that you can use layer masks and blending modes. And you can use this to hand-retouch a channel without wrecking it. Just make a copy into a layer, have it feed into the original channel, and then brush away. You see the changes live, and never touch the actual channel.
The amount of flexibility this brings to channel operations is mind-boggling. But it has not been tested much. So have at it, and report back how it works for you.
BTW, I did not invent this technique. It was suggested to me during a conversation with a user named Witkacy over in the Photoshop featurerequest group. I immediately began testing this and I'm posting everywhere I participate so others can try this out.
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