|This Article Features Photo Zoom|
But this post isn't about how to sharpen. It's about the downside of sharpening—the artifacts and problems that you can create in your digital image files by sharpening too much. So keep reading to find out how to minimize sharpening problems and keep from oversharpening in the first place.
The best way to eliminate sharpening artifacts is to keep from oversharpening in the first place. How do you do this? You sharpen deliberately. The Threshold slider in Photoshop's Unsharp Mask filter (a favorite sharpening tool for many photographers, myself included) is a powerful tool. With it you can dictate what types of edges are sharpened in a photograph. To understand this fully, I'll back up for a second and explain how sharpening works.
The Amount and Radius controls in sharpening tools like Unsharp Mask dictate, as you can tell, the amount of sharpening and the radius (measured in pixels from the contrast edge) of the affect. But it's the Threshold that determines which edges will be affected. A higher threshold limits sharpening to the biggest, boldest edges in a scene (like shoulders in a portrait), whereas a lower threshold allows every edge to be affected—including all those hairs and pores. The problem this illustrates is the added sharpness in things like pores and hairs (not to mention blemishes and flaws) is almost never desirable. The faux sharpness exaggerates problems and creates one type of sharpening artifact: the added appearance of noise-like texture that comes from giving more pixels more defined edges. To eliminate this, start with a higher threshold and lessen the amount of the sharpening. Concentrate on sharpening more significant contrast edges to minimize this grainy, noisy, hypertextured variety of oversharpening.