Chapter 1. What Is Sharpening?

And How Does It Work?

An old saw in photography goes, "If you want great prints, use a tripod!" While it's usually delivered half-jokingly, the important grain of truth is that one of the ways our brains try to make sense of the world as seen by our eyes is by breaking the scene down into edges and non-edges. If the edges in an image appear too sharp or not sharp enough, our brains tell us that there's something wrong, and the image appears unconvincing.

Sharpening is arguably one of the most important yet least understood aspects of digital image reproduction. Examples of badly sharpened images are easy to findyou probably need look no further than your daily newspaper. Good sharpening, on the other hand, is invisible.

Sharpening can't fix sloppy focus or insufficient depth of field. What it can and should do is to make sure that the sharpness of the original capture is carried through faithfully to the final output. Of course, sometimes we also use sharpening to improve realitywe may add some extra snap to the eyes and hair in a head shot, for example. But the primary purpose of sharpening is not to rescue overly soft images, but simply to counteract the inevitable softening that happens when we turn photons into pixels and pixels into marks on paper.

In Chapter 2, we'll look at the various factors that give rise to the need for sharpening, but before we examine those, let's look at how sharpening works, whether it's done in a wet darkroom using analog tools, or accomplished digitally either in the camera or in Photoshop.