Sharpening puts Icing on the Cake

Dennis Faas's picture

A good picture needs to be in focus, but with the digital image we have to be careful not to OVER sharpen.

With the old film camera, I want to count the hairs on the head in a portrait and this meant using a good sharp lens, and fine grain film.

Things have changed with digital photography, the camera wants to blur the image, make it "out of focus" to hide "noise." Every manufacture has their own ideas on fuzzy photos, Canon likes a "softer" image to eliminate those spots in the picture, but Nikon doesn't mind the noice and keeps it sharper.

However, most assume the first think to do when opening a file up in the computer is sharpen it. Software like Picasa doesn't even give you a choice, it automatically resamples and sharpens. But sharpening is the last thing to do.

Sharpening "puts the icing on the cake," says Jim Rich and Sandy Bozak in their book Photoshop in Black and White. They urge prepress technicians to tone the photo first, adjust the highlights, shadows and midtowns, and then apply sharpness at the end.

The computer resharpens by combining the unsharp image with an even more blurred copy (mask) to produce the sharpening effect and this gives it the name Unsharp Mask (USM).

USM adjusts the unsharp original by using the "Threshold" (noise reduction), "Radius" (kernel size), and the "Amount of Contrast."

All these settings vary with any photo, subtle colors, harsh light, how it will be ouput and personal taste determines the best settings.

I like how Microsoft's Digital Image 2006 gives me all the sharpening options when I open the Unsharpen Mask window. Hit the "automatic" adjustments, sharpen, sharpen more and sharpen portraits and I see the changes made to the radius, threshold and contrast setting and it lets me make adjustments, so it will look the way I want it to look when it gets printed. (FYI, different printers means different sharpening.)

Adobe's Photoshop CS2 and Elements 4.0, however, only lets me click on "sharper, sharpen edges and sharpen more," with no chance to make any modification. Also, in Photoshop I need to open several windows, Filters --> Sharpen --> Unsharp Mask.

With Digital Image it's simpler and faster, it works, and when it looks good, hit "Done."

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Tips: Most times changing the Amount of Contrast is all that needs modifying. Threshold should be left at zero, so all shades get sharpened and Radius should not exceed 1.5 pixels to avoid creating haloes around objects.

jgd 11/13/2004

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