Unsharp Mask Sharpening Tips

Today’s Post by Joe Farace

When looking at photographs, the first thing that your eyes see is sharpness, followed by brightness and then warmth. But there are degrees of sharpness and depending on how the images are captured some may be sharper than others.

One of the advantages digital imaging has over shooting film is the ways that you can sharpen images. Most image editing programs contain a Sharpen command that works by raising the contrast of adjacent or edge pixels but sometimes this technique increases sharpness at the expense of contrast. Some photographs can handle additional contrast before loosing highlight detail, while others can’t.

Instead of using the Sharpen command a better way to increase an image file’s sharpness might be using the Unsharp Mask (Filter > Sharpen > Unsharp Mask) command that’s found in  Photoshop and other image enhancement programs. The Unsharp Mask dialog box offers three sliders to control the amount of sharpness applied:

  • The Amount slider controls the percentage of sharpening. Don’t be afraid to apply more than 100 percent to high resolution files but low res images may fall apart if larger amounts are used.
  • The Radius value varies depending on subject matter, final reproduction size and output. For high-res images, a Radius value between one and two is typical. Lower values only sharpen the edge pixels, whereas a higher value sharpens a wide band of pixels.
  • The Threshold slider lets you determine how different the sharpened pixels are from the surrounding area before being considered edge pixels. Using a threshold of four affects all pixels with tonal values that differ by four or more. If adjacent pixels have tonal values of 128 and 129, for example, they’re not affected.

Tip: Here’s a technique to deal with color fringing that can occur when applying Unsharp Mask. After sharpening the image, go to the Fade command (Edit > Fade Unsharp Mask) that appears only after a filter is applied. Don’t change the Opacity setting—leave it at 100%—but select Luminosity from the pop-up menu. Any glaring color artifacts should then be gone.

How I made the shot: I photographed Jennifer using the lighting above setup. A 320 Ws Photogenic monolight with a strip light is at camera left and placed near the ceiling. The main light, another 320 Watt-second Photogenic monolight with softbox attached is at camera right and set between one-quarter and one half power, while the hair/background light was set at three-quarters power. Camera was a Canon EOS 5D Mark I with EF28-135mm f/3.5-5.6 IS USM lens at 109mm. Exposure was 1/125 sec at f/16 and ISO 100.

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