There are as many ways to retouch a portrait as there are faces to be photographed—or so it may seem. But I find myself returning to a handful of techniques over and over again. One of them, in particular, is designed not so much for removing imperfections as it is for imparting a hint of glow—helping achieve the ever-popular look of radiant skin. It involves isolating the red channel in Photoshop to increase luminosity, and here’s how I do it.
With a portrait image file pulled up in Photoshop, open the Channels palette (found under the Window menu) and click on the Red channel to make it active. It will appear as if the image has turned to grayscale because you’re seeing luminosity in place of color, but rest assured the image is still in full color. Next, select all (Command/Ctrl+A) and copy it (Command/Ctrl+C) then click on the RGB layer to bring the image back together to see it all in full color. Now click Command/Ctrl+V to paste the red channel onto a new layer atop the rest.
Next, open the layers palette and you’ll see there’s now a “Layer 2” on top. This is the red channel pasted as a new layer, and it’s why your image once again appears to be black and white.
To get the image back to color, click on the layer mode dropdown menu in the layers palette and choose Luminosity for the top layer. Not only does the image go back to color, but also Photoshop is now using the red channel to determine the luminosity of the image. That’s the brightness, put plainly, and you’ll notice that everything looks lighter—maybe too much lighter, in fact! It probably looks great on the skin (if a bit overdone) but doesn’t do much for lips, eyes, hair and the colors elsewhere within the scene. To fix this, we want to apply the red channel luminosity to the skin and only the skin with a layer mask.
You could simply click to create a new mask on the layer in the layers palette and then paint away all the places you don’t want the red channel’s luminosity to show through. A shortcut, though, is to use the Color Range selection tool to choose just the skin tones in the picture. To use it, look for Color Range under the Select menu; clicking it opens up a palette with a black-and-white preview. Clicking and shift-clicking on areas you’d like to add to the selection (other skin tones) will show in lighter areas of the preview so you can see that just the skin is selected. Alt-clicking (or option-clicking on a Mac) subtracts tones from the color range selection.
When the selection appears close enough, click okay to render it and then click on the New Mask icon in the layers palette to apply the selection as a mask. This will show that only the skin tones are now brighter. Check this by toggling the layer preview on and off. If it’s broadly too strong, dial down the layer’s opacity. In the example shown here, it’s been turned down to just 65 percent, which is plenty for a light, luminous look.
You can further refine the mask by clicking on the mask thumbnail in the layers palette to ensure it’s active, then use a paintbrush set to a large, soft brush size and a low opacity to paint away areas you don’t want to be lightened (like lips, eyes and hair) or paint in areas you do want to add brightness to. When I’m satisfied with how it looks, I like to merge the luminosity layer and the background into a new layer on which I can do further editing to retouch imperfections and generally polish up the picture. This technique is a great way to add glow to skin. And as is so often the case, a little bit of the effect goes a long way toward better photographs.