Sharpening grainy photographs

Having completed my neutral discussion of Unsharp Mask, king of the Sharpen filters, I hasten to interject a little bit of commentary, along with a helpful solution to a common sharpening problem.

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Figure 10-12: The results of applying nine different Threshold values. To best show off the differences between each image, I set the Amount and Radius values to 500 percent and 2.0 respectively.

First, the commentary: While Amount and Radius are the kinds of superior options that will serve you well throughout the foreseeable future, I urge young and old to observe Threshold with the utmost scorn and rancor. The idea is fine — we can all agree that you need some way to draw a dividing line between those pixels that you want to sharpen and those that you want to leave unchanged. But the Threshold setting is nothing more than a glorified on/off switch that results in harsh transitions between sharpened and unsharpened pixels.

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Figure 10-13: The effects of the three preset sharpening filters (top row) compared with the Unsharp Mask equivalents (bottom row). Unsharp Mask values are listed in the following order: Amount, Radius, Threshold.

Figure 10-13: The effects of the three preset sharpening filters (top row) compared with the Unsharp Mask equivalents (bottom row). Unsharp Mask values are listed in the following order: Amount, Radius, Threshold.

Consider the picture of pre-presidential Eisenhower in Figure 10-14. Like so many vintage photographs, this particular image of Ike is a little softer than we're used to seeing these days. But if I apply a heaping helping of Unsharp Mask — as in the second example in the figure — I bring out as much film grain as image detail. The official Photoshop solution is to raise the Threshold value, but the option's intrinsic harshness results in a pockmarked effect, as shown on the right. Photoshop has simply replaced one kind of grain with another.

These abrupt transitions are quite out of keeping with Photoshop's normal approach. Paintbrushes have antialiased edges, selections can be feathered, the Color Range command offers Fuzziness — in short, everything mimics the softness found in real life. Yet right here, inside what is indisputably Photoshop's most essential filter, we find no mechanism for softness whatsoever.

Figure 10-14: The original Ike is a bit soft (left), a condition I can remedy with Unsharp Mask. Leaving the Threshold value set to 0 brings out the film grain (middle), but raising the value results in equally unattractive artifacts (right).

Sharpened, Threshold: 0

Figure 10-14: The original Ike is a bit soft (left), a condition I can remedy with Unsharp Mask. Leaving the Threshold value set to 0 brings out the film grain (middle), but raising the value results in equally unattractive artifacts (right).

While we wait for Photoshop to give us a better Threshold — one with a Fuzziness slider or similar control — you can create a better Threshold using a very simple masking technique. Using a few filters that I explore at greater length throughout this chapter and the next, you can devise a selection outline that traces the essential edges in the image — complete with fuzzy transitions — and leaves the non-edges unmolested. So get out your favorite old vintage photograph and follow along with these steps.

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Photoshop Secrets

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