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Tuesday, August 16, 2011

Creative Sharpening

Use Unsharp Mask for artistic effects


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3a) Image with Unsharp Mask at high Radius 3b) Unsharp Mask high Radius settings
5. Now move the Amount slider back and forth; you'll see the halos and lines increasing and decreasing in contrast.

6. Move the Threshold slider back and forth;
you'll see the effect dropped out of a varying range of adjacent values.

While you're sharpening, keep an eye on these image elements: contours or halos and lines (hard or soft, thick or thin); texture; noise (light/dark or color); contrast; and saturation.

Now that you know how the filter works, how to control it and what to look for, what effects should you consider? There are two primary ways to apply Unsharp Mask: use a low Radius or use a high Radius.

Low Radius applications of Unsharp Mask strengthen the contrast of contours more than their thickness and often can accentuate texture aggressively, for better or for worse. Start with an Amount of 500%. Raise the Radius until it produces an effect that's unnaturally contoured and textured, then pull back slightly. Reduce the Amount to subdue the effect somewhat until the effect seems convincing. Use a minimum Threshold setting or else the effect may be suppressed unnecessarily and sometimes unnaturally. The idea behind this classic effect is to create a very intense line for maximum effect and to make it very thin so the eye can barely resolve it. Use a maximum Amount, a very precise Radius and a minimum Threshold. When using this effect on high-resolution files, because there are more pixels in a high-resolution image, Radius settings will be higher, you'll be able to set them more precisely, and you'll be able to use higher amounts. Higher-resolution files can be sharpened more precisely.

High Radius applications of Unsharp Mask strengthen the thickness of contours more than their contrast and don't accentuate texture aggressively. Start with an Amount of 100%. Raise the Radius until it produces an effect that's unnaturally contoured and textured, then pull back until the effect seems convincing. Use a minimum Threshold setting or else the effect may be suppressed unnecessarily and sometimes unnaturally. High Radius effects are often less aggressive or dramatic than low Radius effects. For this reason, they're often combined together in multi-pass sharpening routines.

You can sharpen an image multiple times and achieve a different effect than sharpening an image only once. How? First apply one type of sharpening and then the other. Typically, high Radius settings are used before low Radius settings, taking care not to create sharpening artifacts in the first pass that will be accentuated adversely in the second pass.

In the November issue of Digital Photo Pro, we'll get into using Unsharp Mask with Layers to modify sharpening effects.

John Paul Caponigro, author of Adobe Photoshop Master Class and the DVD series R/Evolution, is an internationally renowned fine artist, lecturer and workshop leader. Get over 100 lessons with his free enews Insights at www.johnpaulcaponigro.com.


 

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