Real World Image Sharpening with Adobe Photoshop CS2
| Creative sharpening is the catch-all term for localized adjustments to detail. I include blurring as well as sharpeningone way to make a subject appear sharper is to blur its surroundings a little. Unlike the optimizations for source, content, and output processes, creative adjustments can't be applied automaticallythey require creative judgment, hence the name. But automation plays an important role in making many of the tools I use to do creative sharpening. The only part of the process that can't be automated is the actual localizing of the effect to a specific area of the image. So in this section I'll discuss building creative sharpening (and blurring) tools, and applying them effectively to images. The first valuable lesson to learn is that you can turn any adjustment into a brush! Effects Brushes
You can turn any adjustment into a brush using three simple steps:
This deceptively simple technique offers very precise control over localized sharpening. Figure 5-40 shows the steps for creating a simple sharpening brush. Figure 5-40. Creating a simple sharpening brush
Tip: Option-Merge Visible Option-Merge Visible (which when recorded appears in the Actions palette as Stamp Visible) is an invaluable tool for creating layers with merged copies of the image as a basis for sharpening. In Photoshop CS2, it behaves a little differently from previous versions in that it isn't always necessary to create a new layer before choosing Option-Merge Visible, or pressing Command-Shift-Option-E. If the image already contains at least two layers, Photoshop will add a new one automatically. However, if the image only contains one layer, Option-Merge Visible does nothing. So if you record Option-Merge Visible in actions, always record an explicit step that adds a layer before recording the Option-Merge Visible stepthat way, the action will work on flat files as well as layered ones. For a more nuanced sharpening brush, use the Layer Style dialog box to set the blend mode to Luminosity and the layer opacity to 66 percent, then use the Blend If sliders to protect the extreme highlights and shadows. See Figure 5-41. Figure 5-41. Layer Style for a sharpening brush layer
The Luminosity blend mode prevents color shifts, the 66 percent opacity allows you to adjust the strength of the effect up or down, and the Blend If sliders make sure that you leave headroom for the output sharpening. Working with Brushes
When I paint in sharpening or smoothing effects, I always use soft (0% hardness) brushes at low opacities. The softness prevents sharp unnatural-looking transitions between the affected and unaffected areas, and the low opacity helps me "sneak up" on the desired sharpness. Sometimes, though, I'll go too far and paint in more sharpness or smoothing than I wanted. I can press Undo, or go back a few History states, but it's often easier to switch the foreground and background colors by pressing the X key with no modifiers, then paint the offending adjustment out by painting black on the layer mask. Tip: Use before-and-after viewing When you're aiming for subtle sharpening effects, it isn't always easy to see the result of your paint strokes because the adjustment is being made gradually. Turning the layer on and off by clicking the eyeball icon in the Layers palette provides a before-and-after view that makes the effect much more obvious.
A Sharpening Brush in Action
Figure 5-42 shows a sharpening brush created using the steps in Figure 5-40, modified by the Layer Style options in Figure 5-41, applied to an image. Adding extra sharpness to eyes is probably the single most common creative sharpening task. Figure 5-42. A sharpening brush applied
The brush layer had very strong sharpening appliedUnsharp Mask at Amount 500, Radius 1.2, Threshold 0but the combination of a 66 percent layer opacity and a 20 percent brush opacity let me achieve a subtle sharpening effect with a few brush strokes. Notice that the layer mask doesn't contain any pure white. The full-strength effect, even with the reduced layer opacity, would be quite grotesque! Applying a much stronger effect than the desired final result, then brushing it in gradually, offers very fine control over the effect: Sharpening Brush Strategies
You don't have to do everything with the brush, though it's often easiest to do so. The goal of the brushing is to localize the effect, and to obtain the desired relative strength of the effect within the brushed area. But in addition to black and white brush strokes, you have two other important controls over the effect:
Sharpening Brush Actions
The grunt work of setting up a sharpening brush is repetitive, and hence is an obvious candidate for actions. You can build a library of sharpening brushes with different Unsharp Mask settings, or you can build a single action and turn on the dialog box for the Unsharp Mask step. Figure 5-43 shows the steps required to create the sharpening brush I used in Figure 5-42. Figure 5-43. Making a sharpening brush action
To use the same action for different sharpening brushes, just turn on the dialog box for the Unsharp Mask step. Or you can duplicate the action and rerecord the Unsharp Mask step (Option-double-click the step) to build a library of sharpening brushes. Special Sharpening Brushes
Sharpening brushes are useful for more than just applying a little extra local sharpness. You can create all sorts of special-purpose brushes that address specific problems. The only limit is your own ingenuity. Here are three examples of special sharpening brushes that I find particularly useful. Depth-of-Field-Brush
You can't really counteract insufficient depth of field any more than you can make out-of-focus elements in focus. But you can produce a reasonable illusion of doing so using the following technique, which combines Unsharp Mask and Overlay/High Pass sharpening. Make a sharpening layer using the steps shown in Figure 5-43, but use the Layer Style options shown in Figure 5-44. Figure 5-44. Layer Styles for depth of field brush
The differences are that the blend mode is set to Overlay, the layer opacity is set to 50 percent, and the Blend If sliders are set to give less protection to the extreme shadows and highlights. Then, instead of the Unsharp Mask step, run Unsharp Mask with Amount 500 percent, Radius 4 pixels, and Threshold 0, and follow it immediately with High Pass, Radius 25 pixels. Then you can continue to add the layer mask and select the brush. The effect is something between conventional sharpening and a mid-tone contrast boost. It's often quite difficult to see the effect while you're painting it in, but turning the layer on and off makes it quite obvious. Figure 5-45 shows its effect on an image. Figure 5-45. A depth-of-field brush
I applied the depth-of-field brush to both the distant elements and to the soft elements in the immediate foreground, producing a fairly convincing illusion of increased depth of field. A Haze-Cutting Brush
The haze-cutting brush is a variant of the depth-of-field brush that's useful for bringing distant elements in landscapes closer. It uses the same techniques as the depth-of-field brush, but incorporates a warming step immediately after creating the sharpening layer. Create the sharpening layer as in the previous examples, then add a Solid Color Fill layer with a warming filter color (the exact color specifications depend on your working space of choicefor ProPhoto RGB I use RGB 255, 173, 45), and set the blend mode to Color and the layer opacity to 6 percent. Then choose Merge Down from the Layer menu or press Command-Esee Figure 5-46. Figure 5-46. Adding a warming step to cut haze
The rest of the technique is identical to that for the depth-of-field brush. Figure 5-47 shows it applied to an image. Figure 5-47. A haze-cutting brush
I applied the haze-cutting brush to the hills in the background. It's often quite hard to see the effect as you're applying it, but turning the layer on and off to see before-and-after views makes it quite obvious. A Texture Brush
Be warned that this is an extreme effect that should be used with caution! Instead of applying a single Unsharp Mask step, it applies Unsharp Mask multiple times with different Radius settings, using the Fade command between each application. It can do a creditable job of creating realistic texture from minute variations in pixel values. To create this kind of brush, use the same technique as for a smple sharpening brush, but instead of the single Unsharp Mask step, do the following:
Then apply the layer mask and select the brush tool. You may want to set the default layer opacity to 50 percent rather than 66 percent, because this really is a pretty strong effect. Credit for this one goes to my friend and colleague Jeff Schewe. Figure 5-48 shows the texture brush effect applied to an image. I applied the brush to the painted walls at an opacity of 40 percent, and to the wooden doors at an opacity of 20 percent. I left the foreground untouched. Figure 5-48. A texture brush
These examples should give you some hint of just how much you can do with sharpening brushes. I will, however, caution you to save their use for the images that really deserve them! Smoothing Brushes
Smoothing brushes are the other side of the coin from sharpening brushes, and use the same basic techniques. You can make simple smoothing brushes by substituting a low-radius Gaussian Blur for the Unsharp Mask step in the simple sharpening brush. But Gaussian Blur can very quickly lead to an unnatural appearance that proclaims digital manipulation. You can achieve a more convincing result if you add a little noise immediately after applying Gaussian Blur to the brush layer. I use the Add Noise filter set to add 25% Gaussian noise with monochromatic unchecked to break up the plasticky-looking digital perfection produced by Gaussian Blur. Figure 5-49 shows a smoothing brush applied to an image (it shows what I would have looked like when I was 25 if I'd known then what I know now! (And yes, I had the hair loss when I was 25.) Figure 5-49. A smoothing brush with noise
Smoothing brushes such as this one are great for fixing skin blemishes and for smoothing out unwanted texture, but if you need, for example, to knock back a distracting background or to smooth out noise in a sky, you really need a smoothing brush that protects the edges in the image. Otherwise you have to take extreme pains to avoid wiping out important detail, such as where the sky meets the skyline. An Edge-Protected Smoothing Brush
I've already shown you how to make an edge mask. But a layer can only have one layer mask, so to combine an edge mask with a brush layer requires a little ingenuity. Here's how I do it. I start by using Option-Merge Visible to create a brush layer, then I use the techniques I described earlier in the chapter to create an edge mask. I load it as a selection, then apply the selection to the brush layer as a layer mask. Next, I choose Layer>Layer Mask>Apply, which applies the layer mask to the layer, then deletes it. The result is a layer that has transparency where the edges would be. Now I can add a brush mask, and brush the blurring in without worrying about getting too close to the edges. Figure 5-50 shows an image before and after the application of an edge-protected smoothing brush. Figure 5-50. An edge-protected smoothing brush
The edge-protected smoothing brush allows me to knock back the distracting textures in the background so that the subjects pops, without having to be particularly careful around the edges. Creative Sharpening Rules
Very few rules apply to creative sharpening, which in part is why I call it creative sharpening! The big ones are:
Ultimately, control of detail is just as important a creative function as control of tone or color, even if it tends to get much less attention. So absorb these techniques and let your creativity flow! |
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