Getting Better Skin Tones

PHOTO Techniques, Sept/Oct 2007

By Ctein Back to

skintones

Getting people to look good in a photograph takes care. You can take a lot of artistic liberties with a tree; a face is another matter. Human eyes and brains are very sensitive to the appearance of skin tones, colors, and textures. In my work, I use a number of techniques and tricks that produce realistic-looking flesh tones.These methods don’t entirely replace the need for pixel-by-pixel hand-retouching, but they drastically minimize it.

The masked layer approach

I just finished a book on photo restoration, so I’ve used photos in need of restoration as examples here. However, I use the same techniques to fix skin (and other) tones in doing my own work. Skin tones in poorly exposed negatives and digital captures often end up with problems similar to those in photos in need of restoration.

Skin tones in old color photographs commonly have two problems. The first is high overall contrast: Tones are usually too harsh, and highlights tend to be blown out, with lines and shadows accentuated. The second problem is blotchy color; high contrast in each of the individual color channels exaggerates what should be more subtle differences in skin hues. Consider Figure 1*—restoring the overall color and contrast of the faded photograph produced faces with some patches that look flushed and others that look jaundiced.

This can be fixed with adjustment layers, and here’s how I did so.

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I used a mask to limit my corrections to the women’s faces. In this case, I decided to paint the mask in by hand; it took me about 30 minutes. For a more complex masking job I’d use a third-party tool such as Mask Pro. For high-quality work, I’d make individual masks for each woman and correct each one’s skin tones separately. In this example I applied the same corrections to all three women’s faces, which wasn’t optimal for any of them.

There are no irreversible mistakes when painting a mask. I started off with a large-radius black brush and painted over the faces and arms of the women. Then I shrank the radius of the brush and filled in the edges. If I painted out too far, I switched the brush to white and corrected my errors. Pressing the “Q” key turns the Quickmask view on and off in Photoshop, so I could inspect the mask directly while cleaning it up. I checked it frequently to make sure I didn’t miss a spot. I inverted the tones to create the mask shown in Figure 2a.

Using this mask to create a Curves adjustment layer (Figure 2b), I set the blend mode on that layer to Luminosity so that it would alter tonal values but not colors. The curve reduced contrast in the midtones and highlights and dropped the maximum density in the highlights.

Figure 3 shows successive improvements I made to the women’s complexions. Figure 3a is the same as Figure 1. Figure 3b shows how the luminosity Curves adjustment layer I just created tames the harsh effects of the on-camera flash.

With the new lower contrast, it’s easier to see the blotchy color problems. To understand what’s behind that, look at Figure 4. From top to bottom, this shows undersaturated. There’s a flat and pasty quality to them, typical of insufficient saturation. A third masked adjustment and less error prone. I added two layers to the photograph (Figure 8) and set Layer 1 to Darken blend and Layer 2 to the Red, Green, and Blue channels of the aforementioned photograph. The Red channel looks great. The contrast in the faces in the Green channel (the magenta hues) is a little bit high, and the contrast in the Blue channel (corresponding to yellow) looks very harsh. It’s that excess contrast in the magenta and especially the yellow hues that causes the blotchy skin colors.

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Figure 5 shows green and blue curves that will substantially soften those problematic colors. I created a second masked Curves adjustment layer with the blend mode set to Color, which produced Figure 3c.

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The skin tones here looked pretty natural, but I felt they were a little bit layer, this time for Hue/Saturation (Figure 6) produced Figure 3d. The complete stack of layers for these corrections is shown in Figure 6, right.

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The airbrushed-layers approach

When faces have pretty good color but too much contrast, a little handwork often does the trick. Consider the partially-restored photo in Figure 7, left.

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I was happy with the color balance, but not with the contrast; there were lots of blown-out highlights in the faces, and the shadows were pretty harsh. I decided to airbrush away these problems. Instead of attacking them directly, though, I created two special retouching layers to make the work much easier Lighten blend. Note that these are not adjustment layers; they’re ordinary image layers.

I selected the Airbrush tool and set its opacity to a very low level of 9%. Activating Layer 1, I sampled the color in the man’s face next to the highlight on his forehead, and started airbrushing over his forehead. Because I had the opacity set so low, I could build up tone very gradually and blend it in smoothly with the surrounding skin tones.

With this layer set to Darken mode and such a light tone in the airbrush, I didn’t have to worry about sloppy brushwork messing up tones that I didn’t want to change. If I had accidentally airbrushed over any of the darker parts of his face or hair, it would have had no effect on the blended image because the color I was painting with was lighter than the Background layer colors. When I did occasionally overextend my retouching, I airbrushed away the excess retouching by switching the brush’s color to white.

I airbrushed any part of his face where I thought the highlights were too bright and shiny. Whenever I airbrushed a highlight, I used color sampled from a nearby area. For example, when I air-brushed the man’s cheeks, I sampled a spot of color right under his eye. When I was toning down the highlight on his chin, I sampled the color between his lower lip and chin. This kind of retouching is really easy; it took me longer to write this that it did to do the work. You’ll probably find that it’s much simpler to do it than to understand my explanation of it.

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The darkening retouching I did is shown in Figure 8, left. As you can see, I didn’t follow the outlines of the face or highlights very closely at all. The results, shown in Figure 7, center, look entirely professional. Blending in light-toned airbrushing like this produces a seamless-looking photograph.

To deal with the shadows, especially those in the woman’s face and hand, I switched to Layer 2, which was set to Lighten blend. I worked the same way I had in Layer 1, using the airbrush at very low opacity and setting its color to one that was adjacent to the shadows I wanted to lighten.

I didn’t try to remove much of the shadowing; shadows define the shape and three-dimensional structure of the faces and hand. Flatten out those tones too much, and you’ll get a very strange look, as if people were wearing flat cardboard masks with pictures of their faces on them. You don’t want to go that far! The shadow work that I did is shown in the center of Figure 8. I made the background black in this illustration so that the airbrushing would be visible as lighter brush strokes against the background. The background of that layer is actually transparent. The combined highlight and shadow retouching produced the photograph in Figure 7, right.

In truth, I overdid the retouching in this example to make sure the changes would show up clearly in the illustration. But my efforts weren’t wasted. A cool thing about having done this work in layers is that I can dial back the strength of my retouching. Dropping the opacity in the two retouching layers to a strength of about 60% gets me a photograph that looks great as a finished print.

The color-airbrushing approach

The Color Airbrush tool is a nice, painterly instrument for correcting blotchy skin colors. In fact, it is good for correcting all kinds of color aberrations when pleasing color is more important than technically accurate results. Like the previously described airbrush techniques, it’s fast, flexible, reversible, and it doesn’t require you to be a great artist to use it effectively.

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The school portrait in Figure 9 was extremely faded when I started. After substantial restoration, I had Figure 9a. That was good enough for me to start working with color airbrushing. I added a new, empty layer to the photograph and set the blend mode to Color—anything I painted into that layer would alter the color of the underlying photograph, but it wouldn’t change its brightness or tonality.

I set the brush opacity to 15%. Note that I used the tool in its Normal mode: The layer-blend setting takes care of how the airbrushing gets merged with the background. If I wanted to paint directly on the original photograph, I’d select Color as the airbrush mode, but then I’d lose the ability to easily revise my work.

Figure 10 shows successive stages of color airbrushing from start to finish. First, I decided to remove the cyan cast that was still present in the highlights on the face and neck. I set the airbrush color to the pink hue of the cheek and brushed over the woman’s forehead, around her eye sockets, across the bridge of her nose and her upper lip and chin, and along her neck (Figure 10a). Her skin was now more uniform in color but too pink. Using a broad airbrush at very low opacity, I selected some brown from her hair, and ran the brush over her skin to produce a flesh tone that I liked (Figure 10b).

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The shadows on the woman’s neck and hair were very magenta, so I selected a yellow-brown tone from her hair and painted over her neck at moderate strength and her hair at high strength to correct those colors (Figures 10c and d). That gave me the photograph in Figure 9b. Her hair and skin color now looked very good, with the magenta shadows warmer and more natural, and the cyan highlights converted to healthier skin tones.

The upper left part of the photograph was stained yellow, so I sampled the background on the right and used the airbrush at about 50% strength to change the color of the stained areas to match the rest of the background (Figure 10e). That got the picture almost to where I wanted it.

The whites of her eyes and the folds of her dress were too cyan, so I sampled a gray tone and used a small-radius brush at 30% opacity to dot in the whites of her eyes, erasing the cyan there. I then ran the brush over the folds of her dress, taking care to avoid the red pattern, making the folds in the fabric much more realistically neutral. The finished Color Airbrush layer is shown in Figure 10f. That layer gave me the photograph in Figure 9c.


About the Author

Ctein
Ctein
Ctein is a technical writer and expert printmaker. He is also the author of Digital Restoration and Post Exposure—Advanced Techniques for the Photographic Printer.