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Tuesday, August 17, 2010

A Sharper Image

How to get images full of crisp details without overdoing it

This Article Features Photo Zoom


For the ultimate in sharpening control, Nik Sharpener Pro makes selective sharpening easy, and adjusts intensity based on output size and expected viewing distance.
The middle slider, Radius, controls the width of the edge sharpening and ranges from 0.1 to 250 pixels. Typically, the Radius is small, ranging from 0.3 to 2.0 pixels. If you see a halo effect around the edges of objects, the Radius is too big. Larger image files can handle higher Radius settings better than smaller files.

Finally, the Threshold slider determines the pixels to be sharpened based on the difference in brightness between neighboring pixels. For example, a Threshold of 3 affects all pixels that have tonal values that differ by a value of 3 or more, on a scale from 0 to 255. So, if adjacent pixels have tonal values of 100 and 102, they’re not affected by sharpening.

For fine details, a higher Amount and lower Threshold work best, while portraits and areas with smooth tones work better with a lower Amount and a higher Threshold.

Each image requires a different degree of sharpening, but here are some guiding points: With portraits, start off with an Amount of 100, a Radius of 1.0 and a Threshold of 6. For buildings or landscapes, try an Amount of 150, a Radius of 1.5 and a Threshold of 3. If there’s a lot of noise in an image, try going up to a Threshold of 10 or 12. Remember, experimentation is key.

Another tool within Photoshop is the Smart Sharpen filter, which allows you to set the sharpening algorithm or control the amount of sharpening that occurs in shadow and highlight areas. One of three sharpening algorithms can be used: Remove Gaussian Blur, Lens Blur or Motion Blur. One drawback to this tool is that it doesn’t have a Threshold setting so it can overemphasize noise.

For Aperture users, the Sharpen and Edge Sharpen tools are good to know. Sharpen has two sliders for setting intensity and pixel radius, and Edge Sharpen has three sliders for setting intensity, edges and falloff. Intensity controls the amount of sharpening. The Edges slider lets you set the number of pixels that qualify as edges to be sharpened, and the Falloff slider produces a more or less pronounced effect.


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