Skin Retouching Tutorial Part 1
How to lie for fun and, maybe, profit.
By Crawford Hart.
This is a topic that often falls outside of the concerns of professional photographers; rather than capturing reality and presenting an honest depiction of what one finds there, this endeavor is concerned with... well, lying. At its simplest, it's an effort to help the subject look their best; at its most extreme, we are creating fantasy pure and simple, with results that are never found in the real world. Ever. No one looks like this, not even Tyra Banks. (She comes pretty close, though).
Perfectly smooth skin is a tricky retouching challenge. It's a series of complex gradients moving not only from lights to darks and from one hue to another but in multiple directions as well. It doesn't take much for the eye to fasten on imperfections and the effort to remove them often creates more problems. Until Photoshop 7, the tool of choice for skin work was the cloning tool (No purer manifestation of evil has ever been found.) It was, and remains, woefully inadequate to the task. The combined challenge of maintaining the smoothness of the gradients without losing believable skin texture made many retouchers reconsider their applications to McDonalds. With PS7 the Healing Brush made it's appearance and music and light once more filled the land of retouching.
There are three ways to approach skin retouching. The most common is to think like a plastic surgeon: you graft skin from a healthy area onto the problem spots and hope you can minimize the scars. But imperfections can also take the form of unwanted variations in dark and light areas. Rather than replacing an unwanted area, we dodge or burn the areas, lightening or darkening just enough to bring them into balance. Sometimes the problem is one of mismatched color, and we must find a way to exploit color correction techniques.
These three approaches constitute 90% of the time you will spend on a serious retouching job. None of them requires arcane techniques; they do require finesse, and, most of all, patience. There is no quick fix for skin, not if the desire is to make it look both flawless and real and to hide your own tracks. None of the whiz-bang effects that LAB produces will be found here. Most of the job entails endless repetition of the same simple moves, with results so slight you'll often wonder if you're accomplishing anything. Until you turn your retouching layer on and off. You get your whiz-bang effect at the end of the job when you compare before and after version.
One technique that has been around forever, and which lives to this day, is to create some form of smoothing layer on top of the offending skin and try to blend it into the original without making it look fake. Whether one paints tones in with an air brush, or tries some blurring moves, this approach is roundly scorned by most magazine editors and, when done too obviously, will not only get the job bounced, it will earn those responsible a place on the "Do Not Use" list. Still, the reason it remains a current technique is that, done right, it works. It is to be hoped that we will do it right.
In this section I will address the three approaches to skin work already mentioned. In Part 2, I will deconstruct a couple of jobs, discuss contrast moves, smoothing, sharpening, how to make skin glow, and other fantasies.
THE HEALING BRUSH
Adobe has described the Healing Brush as "The Cloning Tool on steroids." Somewhat true. While you can often treat it like a cloning tool, one that doesn't require precision and offers superior results, it comes with its own set of quirks, and capabilities that go beyond cloning. For any skin work, it will be one of your primary tools.
First, let's note the most peculiar quirk of the Healing brush. In theory, it retains the color and lightness of the target area, while replicating the relationship between lights and darks from the sampled area, translating the sampled texture into the target range of value and tone. It also performs a kind of magical blending between target and sample, and at the edge of the strokes, without muting detail. While this blending pretty much eliminates the "clone worms" so prevalent with the cloning tool, it can be both blessing and bane.
In these images, we see what can go wrong with the healing brush.
The pattern of fine hairs needs to be smoothed out. It would seem to be a perfect job for the healing brush, given it's blending capabilities. (A) We sample from a nearby region with texture but no hair (B). But the result (C) demonstrates the blending capability of the healing brush, precisely where we don't want it. Part of the problem is that we've made our target area too close to a much darker region, but the main problem is the brush size. The ability to suck in surrounding pixels is a direct function of the size of the brush.
Note the similar target area in (D), but with a significantly smaller brush. The result this time (E) is much more in keeping with expectations.
Rule 1: always keep the size of your brush in proportion to the artifacts that are being dealt with. Even if the overall area that you cover with a single move is much larger, the tendency to pull in unwanted pixels will be determined by the brush size. (On the other hand, if there is a sharp transition that you want to smooth out, replicating the "mistake" of image (A) can become a valued procedure. A few passes on either side of the transition line, pulling the regions into each other, can make for smooth transitions.)
Rule 2: Don't use the healing brush to make drastic shifts in color or value (i.e. removing a dark shadow, or a necklace.) It will make a soupy mess of the job. Prep the area first by using the Dodge/burn techniques or the color moves discussed next, to bring the target into rough balance with the surrounding area. You could even use the clone tool.
Here's an unsightly wrinkle that we're simply going to take out (A). Keep in mind, the healing brush is quite forgiving. You don't need to worry about lining up your sample with your target, you don't need to be particularly precise. (B) shows a typical stroke that I might make, and the result (C). And after four or five similar strokes we arrive at (D).
The question could be raised, "Why use the healing brush for a shadow like this? Why not a dodge/burn layer?" As I will demonstrate, I make extensive use of dodge/burn layers to lighten and darken selective areas. However, unlike the healing brush, dodging and burning requires infinite patience and subtlety. And precision. Large imperfections like this wrinkle are among the first things that I'll attack, and I do it with the healing brush because it's fast. I can be sloppy. I basically scribble over the target area; maybe I'll draw circles, maybe half-moons. It doesn't matter. The healing brush responds to all of it and after a relatively short time, the gross imperfections suddenly become much less noticeable. And much more conducive to the refined shifts that dodging and burning provide.
My initial moves always are with the healing brush. I try to attack everything I see. By definition, if I notice it, it shouldn't be there. So it's only natural that I would deal with deep wrinkles around the eyes and in the face at this point. The healing brush makes quick work of them
Here's a fairly normal pair of eyes (A); however if they were meant for a cover of, say, Elle, the instruction would be "Knock back the wrinkles some." Which means keep it real. Don't do an eye-lift that stretches the skin tight and glossy.
Now, retouching just part of the way is kind of a pain; the usual approach is to set your cloning or healing tool at a low opacity and clone some clean skin over the wrinkle. This is never particularly satisfying; there's almost always a softness and loss of detail surrounding the actual wrinkle.
What is easy, using the healing brush, is to hit the offending wrinkles head on and obliterate them altogether (B). Then cut out the originals from the layer beneath, and put them on top (C). Now you just need to set the opacity to determine how much you will knock them back. This is how they look at 40% (D). There is still some discoloration and unevenness, but it was already there. We'll deal with that in later fine tuning steps. But for deep face, neck and eye wrinkles, this will allow you to keep believability, while repairing the damage.
One last thing to keep in mind, both with the Healing Brush, and with the two techniques that follow: Start close up, at 100%. Then move back out to 50%. Avoid odd scaling values. 66.7% and 33% aren't horrible, but 71.83% would be a disaster. At 100%, there is a one-to-one ratio between screen pixels and image pixels. 50% and 25% yields results that compress the pixel information evenly, much the same as happens when you print at actual size. Odd scalings create interference artifacts from uneven interpolation of image pixels to screen pixels. At even scalings, you will see artifacts that weren't apparent at 100%, and you can trust that they are actually there. So you will want to make several passes, zooming out each time and dealing with the new problems that show up.
You won't get it perfect with the healing brush, but as you can see here, sudden transitions with their obvious edges are easy to remove. And now the imperfections that remain can be dealt with much more effectively by the next technique.
DODGING AND BURNING
The healing brush's value is the ease with which lots of gross imperfections can be brought under control without a loss of skin texture. But if you want to take that next step to flawless skin, you will need to dodge and burnagain, and again and again.
With the healing brush i will try to cover as many bases as possible before moving on. Dodging and burning is never finished. Sometimes the problems that it has to address don't become obvious until other steps have been completed. A typical work flow might look something this:
You get the idea.
A quick search of any number of Photoshop forums will turn up a variety of approaches to this task. I'll be honest, I haven't tried most of them; I found the version I like and it's never let me down. If you wish to embellish or modify this technique, by all means, do so.
None, by the way, involve actually using the Dodge/Burn tools on the image pixels themselves. Don't even think about that. They all involve placing dark and light tones in a layer or layers above the image with the intention of countering unwanted variations in the lights and darks. Usually, this layer will be in Hard Light, Overlay or Soft Light mode. All three modes interact with the underlying pixels to create lighten or darken effects.
In all three modes, 50% gray has no effect at all. Hard Light and Overlay will screen tones lighter than 50% against the underlying pixels, and multiply tones that are darker. With Overlay, the effect diminishes as the underlying pixels approach white and black, concentrating the effect in the quarter tones and three-quarter tones. A layer filled with white in Overlay Mode will bleach out most of the image, but the shadow detail will be retained. Hard Light mode affects the highlight and shadow detail as well and as a result, produces a much stronger effect. To be honest, I'm not sure what Soft Light does. It's similar to Overlay in that highlights and shadows are retained, but the effect is, well, softer. The best way to see the difference is to place a layer above any image you choose, fill it alternately with white and black in each of the three modes.
Painting light or dark colors in a layer in any of these modes will result in lightening or darkening of the image. There are endless variations: filling a layer with 50% gray and using the Dodge and Burn tools on that neutral color; creating a multiply layer and a screen layer and alternating the use of each one, depending on whether you wish to dodge or burn. I like simplicity and a minimum of steps (very important with a procedure that you will repeat endlessly) so I create a transparent layer in Hard Light mode. There's no need to fill it with 50% gray; it has no effect other than to make it easy to see your stroke if you isolate the layer.
Whatever mode you use, the key is a small brush, low opacity and a pressure sensitive tablet. I set my brush to 5% opacity and my tablet pen opacity mode to pressure, and I vary the size in direct porportion to the artifacts I am modfying. It's better to build up many small strokes over an area than to try to cover everything with one or two large strokes.
The colors I choose to paint with depend on the image. Often, white and black work just fine, as the only thing we are trying to do here is alter the lightness value of discreet parts of the image. However, sometimes you will run into saturation and hue problems using this approach: merely lightening a dark area or darkening a light area can yield values equal to the surrounding pixels, but with colors that desaturated to blend. It's often a good idea to sample from the lightest highlight (that hasn't gone to white) and darkest shadow (that hasn't gone totally to black.) Setting one color to foreground and one the background, it's a simple click of the "X" key to change them around. That's the beauty of this approach: one tool (the brush) one layer, one key stroke to switch from dodging to burning and back again.
Here is where accuracy is required. The imperfections that you are targeting are small to begin with, and as you progress, they become ever more subtle. If you're not accurate, you'll simply create new artifacts, rather than eliminate those that are already there. It's hard to demonstrate dodging and burning in separate images, since each move is so slight. So here's a before and after shot, with the dodge/burn layer. I set the strokes against 50% gray so they can be seen. In practice, I usually don't bother. Filling with gray is just one more unnecessary step that I don't want to take the time to do. Don't try to count the strokes; it's too depressing. An advantage of switching dark and light colors on the same layer is that you can almost run on automatic pilot; the process of adding strokes becomes a kind of zenlike activity where you don't really notice time passing. It's a small price to pay for beauty.
COLOR IMPERFECTIONS Note the unfortunate skin blotches on this otherwise cute little baby. This image comes from a thread where a genuine whiz-bang LAB technique was discussed, and which is certainly relevant to any discussion of skin imperfections, particularly color problems. That thread is here. I highly suggest acquiring facility working in LAB, in general. As this thread shows, some valuable tools are available that you won't find in other spaces. However, this is about retouching and there's no point rehashing LAB discussions that have been dealt with in far greater depth elsewhere.
I took a more conventional approach, using selective colors and a variety of other tricks, eventually bringing me to this unsatisfactory point.
The red areas are too extensive to yield to the healing brush, and dodging won't really solve the problem. The color problem will still be there even if we get the values in sync.
Whenever I have a problem like this one, I like to treat it like a simple color correction issue. I have one area that I don't like, and another area that I'd like to match. It's a perfect problem for a set of curves to solve; the only problem is creating a decent mask through which to engineer the shift. My solution is to work backwards.
First, I set a color sampler in the middle of the triangular patch of skin just to the left of the nose, as the tone I wanted to match. Then I set a second sampler somewhere in the middle of the red blob just to the left of the first area. The red sampler read R:209, G:135, B:108. The clear sampler read R:229, G:182, B:156.
Next, set a curve adjustment layer and fill the layer mask with black. Make sure that the gradient at the bottom of the window has black on the left. now set a midpoint in each of the channels, plugging in the values as they appear in the info palette. In the red curve, with the midpoint selected, you would enter 209 for Input, 229 for Output. In the green curve use 135 for input, 182 for output, and in the blue curve use 108 for input, 156 for output.
The next step is identical in mechanics to using a dodge/burn layer. Small brush, low opacity, painting incremental strokes of white into the mask, letting the curve begin to work on the red skin. Here is the mask that evolved, and the result it produced. You can see from the brush strokes that I used a wide variety of sizes and opacity settings (the result of keeping my pen in pressure sensitive mode).
The beauty of using a curve like this is that, rather than painting in a single color in color mode, you are applying a full color range. Even though I only entered values from a single sample in each region, the curves distribute the shift over the entire spectrum. Not only do all the regions lighten and shift color, but by painting more white into darker or redder regions those tones can easily be brought into balance with the surrounding pixels.
Acne and freckles respond quite well to this approach. It's also good for gross color shifts, such as lightening shadows. It avoids the saturation problems of dodging away at the shadow and finding out that it's basically a neutral color.
...AND THE KITCHEN SINK
When to use which technique? Seldom does a job allow you to separate out each step. There is a lot of overlap, areas where you could dodge a shadow or just as easily hit it with the healing brush. Then there are times when you're not sure if anything would be effective.
Image (A) shows a really harsh shadow. It needs to be softened, lightened, smoothed and the purple cast needs to be pulled more towards brown. This is a job that will take everything we can throw at it, including the kitchen sink. (Note: the clearly defined area also makes this a perfect candidate for the LAB modification mentioned in the previous section).
I first sampled a shadow that was a more pleasing color and used that as my match values for a curve modification. The mask that I painted is at (B) and the result at (C).
This is an improvement, certainly more compatible with the healing brush, which is what I hit it with next (D). I wasn't trying to wrap things up with this step, so I didn't worry much about being sloppy. I mostly wanted to smooth out the fine hairs, and blend the patch more with the adjacent skin.
Now it's time to dodge and burn. I sampled a highlight and shadow from the rest of the face. (E) shows the hard light layer with my dodge/burn strokes and (F) the result. Still irregular, but the overall tones are much more balanced than in (D). And the areas are small enough that a final hit with the healing brush gets us to (G), and the beginnings of a real patch of skin.
This example isn't perfect, and I'm not sure I'd have done everything this way in a full retouch of the face. But it shows that none of these techniques are isolated. And they're all focused on the same result: removing any anomaly that stands out from otherwise smooth, flawless skin. All the while retaining the illusion that this really is normal skin; skin with texture and pores and maybe even a stray line or two. It's just real skin that's infinitely more beautiful than yours.
And with this image, we will confront head-on an issue raised in a dGrin thread: "How far should we go?" In this case, the answer is "At least back to 1986", because we'll peel about twenty years away from his face. Discuss these techniques on Dgrin in this thread.