Sample image file included at the end of this post, if you wish to follow along!
Today, we’re going to “rebuild” RGB channels. This technique comes in handy if a couple of your original RGB channels have a lot of information, but at least one of them is in horrible shape. In the example photo, when a curves adjustment layer is applied for color correction, the sky area in the upper right hand corner is pretty trashed.
While I can fix it using traditional methods, of course, I don’t always want to take the time, or, perhaps, I want a nice black and white treatment of the photo, either for its own sake, or to apply colorization. As you can see by the channel images below, the red and green channels are in good shape, but the blue looks rather bad.
I think you’ll all agree with me that the green channel is the best of the three, but we’re going to toss it out with the blue, anyway. “Why?” you say; because, for the purposes of this tutorial, I want the best, lightest channel available! Sometimes, that will be the green, if, say, the red channel is the worst, but, in this case, the best choice happens to be the red. In the channels palette, select the red channel.
Select Image > Mode > Grayscale. Click OK when the dialog box pops up. The unused channels will be thrown out. Now, we begin rebuilding. Select Image > Mode > RGB Color. You now have channels again, but they’re all the same. Select the green channel.
Select Image > Apply Image. Make sure the channel field is on Green and the Blending Mode is set to Multiply and Opacity, 100%. Click OK. Now, in the Channels palette, select the blue channel.
Repeat the previous step (Image > Apply Image). Make sure the channel field is set to Blue, Blending Mode, Multiply and Opacity, 100%. Click OK. Now, do that step over. Yes, Apply Image to the blue channel, twice!
Notice the color is a heavy sepia tone, now. I do whatever little restoration needs to be done, now. Needless to say (although I guess I am saying, anyway), it’s much easier, now.
Now, in the Adjustments panel, go to the Black & White filter. This is a matter of choice, depending on the black and white look you like. You can leave it on the default option, if you like, but I like to go through all the options to see what looks best and (or) suits my needs. I like the Maxim Black option, the best.
I’d probably keep it there, if I were going for a straight Black and white, but it’s a bit too dark for colorization. So I opt for the Auto button, which gives me a nice light to medium dark look.
I could have, instead, used the original green channel, the best channel in this example, and made one channel lighter (using the Overlay mode in the Apply Image dialog box), to become the red channel, and another darker, to become the blue channel. Different approach, very different results. I find that method results in a better sepia tone, with the addition of a Curves adjustment layer, rather than black and white.
So, that’s how we “rebuild” RGB color channels! As always, experiment, try different things! Using non-destructive layers allows you to try, retry and trash as many times as you need to come up with the look you want. Have fun!
File: “Eddyville” (Photo property of Landailyn Research & Restoration, private collection)
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