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Digital Grin > Beyond Basics Review of Blending Modes Displacement Maps 1 Displacement Maps 2 Skin Retouching, Pt. 1 Skin Retouching, Pt. 2 Skin Retouching, Pt. 3
Digital Grin > ADDING DETAIL Up until now, the steps have been pretty straight-forward, and the goals clear. Now it becomes slippery, in that there are an infinite number of ways to set the appropriate values to get the effect desired. It's a matter of taste and preference. I'll take you through the settings that I chose, and try to explain why (not always an easy thing) but it's not as important to match my approach as to become comfortable with what is actually going on. Keep in mind, your numbers will be different. In fact, were I to do this again, my numbers would probably be different. And any of these parameters can be enhanced, modified or expanded. We have four layers to work with. The goal will be to apply the High Pass filter to each of them, with a distribution of radius settings that more or less evenly captures a full range from small to large detail. Once we determine the initial radius, we can then determine the settings for the remaining three layers by simply reducing the settings each time by an equal value. But what should that initial radius be? Recall that with a Gaussian Blur, we knew the setting that would return the blur to its original state: it was the same as the Blur radius. We don't have the same precision here, but it's pretty easy to increase the radius of the High Pass filter until the image looks more or less like the original. Our starting radius will then be a value lower than this. (Remember, we're trying to minimize the large detail.
Digital Grin > THE WORKFLOW It's always a good idea to apply some conventional retouching to the image before embarking on this procedure; large blemishes, warts, brusies, lines and discolorations should be minimized as much as possible. But you don't need to be a fanatic about it. As I said at the outset, I performed no retouching on this image before taking it through these moves, though, as I mentioned, the skin was in good condition to start with. Sometimes, though, it helps. • Copy the original (or merged layers) into five new layers. • Name the first layer Blur and leave it in Normal mode at 100%. • Change the other four layers to Linear Light mode and set their opacities each to 50%. Turn them off for now and return to the Blur layer.
Digital Grin > While the Gaussian Blur filter is well-known, the High Pass Filter is a little stranger, less user friendly and not so easily understood. It is often used for various sharpening moves. Depending on the radius, it reveals fine detail against a 50% gray background. The larger the radius, the more detail is exposed. When used as a sharpening tool, the idea has been to combine the resulting layer with the underlying image in one of the modes that both lighten and darken, based on the value of the pixels on the top layer. The usual modes are Soft Light, Overlay and Hard Light, modes for which 50% gray has no effect and so only work on the level of detail revealed.
Digital Grin > THE BASIC IDEA The theory sound simple enough: blur the big stuff and leave the small stuff alone. We want to lose the blotches but keep the pores and other fine details that make skin texture believable, and, the lack of which, conjours up the dreaded judgment "AIRBRUSHED!!!" But if it sounds simple, it also sounds impossible, until we actually explore the relationship between blurring and sharpening in Photoshop, specifically between the Gaussian Blur filter and the High-Pass filter. Rather than get into an elaborate discussion that is ultimately beside the point, try this yourself with any image you wish. Or you can just watch me as I play around. NOTE: If you chose to pull the example images posted here, your numbers will be different than mine. I worked with an original Hi-res image; these are scaled down for the purposes of illustrating the steps.)
Digital Grin > By Crawford Hart.Part 1 of this series provided an overview of some of the generally accepted approaches to the problem of achieving perfect skin. The techniques themselves aren't glamorous, though the results can be. They tend, rather, to be boring, repetitive, simple procedures, tasks in which the operator must do most of the work. Grunt work, in other words. Part 2 (the one you're reading now) and Part 3 (to come) will shift over to those effects in which Photoshop does the work and we just add up numbers and push buttons, though a little bit of delving into the esoterica of Photoshop, how it works under the hood, will be called for. But the payoff is definitely worth it. The ideas behind the process discussed here certainly did not originate with me; they can be found on other forums all over the web. I've provided my own particular slant, as I would expect you to do, once you're comfortable with the basic ideas.
Digital Grin > For this image, a radius of 30 pretty much replicated the original state. So I reduced the setting to 20 and that became my starting value, the results shown here. Compare it with the third image (the starting image) and you can see that we've already begun smoothing some of the blotchiness away. Our ending value will almost always be a radius of 1 pixel (occasionally less, but not often), so it's simple arithmetic to figure out the intervening settings. I chose 20, 13, 8 and 1 as the settings for each of my High-Pass Layers.
Digital Grin > Note how effectively the High-Pass layer can restore detail to the blurred layer underneath, when used in the modes previously mentioned. All of these are at 100% opacity. If you turn off the blurred layer, so that the High-pass layer is blending into the original image, you will see how the filter can be used as a sharpening method. It's effective, but not nearly as effective as it will be once you understand what is really happening and can exploit the effect to its fullest potential.
Digital Grin > THE LENS BLUR The Lens Blur filter was introduced in PS7, I believe, and its primary function is to mimic depth-of-field effcts. It uses a grayscale alpha channel to determine how much blurring to apply to different parts of the image. A properly applied gradient from white to black can create a believable effect of blurring increasing with distance. It is far cleaner than trying a similar operations with the gaussian blur. It adheres to the mask precisely, with no pixel/color bleed. And we're not using gradients. Our only concern is with black and white areas—to blur or not to blur. I've been using a Lens Blur in place of Gaussian Blur, with superior results. The downside: the radius settings don't seem to match those of the Gaussian blur, so you will need to work a bit more intuitively. This, as it turns out, is not too hard to do. So, shiny new skin mask in place as one of your alpha channels (named, hopefully, skin mask, or something to identify it), let's see how it works. When you open the Lens Blur Filter, there is an impressive and daunting array of parameters. I haven't found much use for any of them other than Radius, Shape and Distribution. • At the top under Depth Map, select the alpha channel with your mask (which, if named properly, will be easy). • Leave the Blur Focal Distance at 0. If your preview shows the blurring happening in reverse, check the Invert box. • I use the Hexagon shape because it seems to be stronger. It's not really important. Choose to taste. ª At the bottom I check Gaussian for Distribution. • It's the Radius slider that is of interest. By now you should know what it is we're looking for with this step. Vary the setting until you have those smoothly blurred areas of color. If you see that you are losing some shadow detail, or that you are getting some color drift from shadow areas into skin tones, click Cancel and return to your mask and paint them out. Notice how in the mask I drew, I excluded the nostrils. Once your preview is to your liking, apply the filter. It takes a bit longer than a normal Gaussian Blur, and the result is a little strange. Sharp eyes and mouths in a smooth sea of washed out skin. But that will change.
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