… for Visual Effects

Tip #450: What Does Sharpening Do?

Larry Jordan – LarryJordan.com

Sharpening adjusts the apparent focus of a clip.

Sharpening adjusts the apparent focus of a clip, without actually changing its focus.

Sharpening adjusts the contrast at the edges of objects in an image to improve their apparent focus. What our eye sees as “focus” is actually the sharpness of the edges between a foreground object and the background. If the edges are sharp, our eye considers the image in focus. If not, we consider the image – or that part of the image at least – blurry.

Unsharp Masking (which is the preferred method of sharpening) enhances the contrast between two adjacent edges. Our eye perceives that improved contrast as improved focus, though nothing about the focus of an image has changed.

When using Unsharp Mask, a little goes a long way. A Radius setting between 1.5 and 4 will yield perceptible results without making the image look like bad VHS tape.