The Low Light Photography Field Guide

Identifying Blur for Repair

There are two basic kinds of blur, which is to say two basic causes of unsharpness. One is focus blur, in which point sources in the subject reproduce not as points but as discs, and the other is motion blur, in which features in the subject that should be sharp in the image reproduce as streaks or smears. And there is every possibility that both kinds of blur appear combined.

Let’s first consider focus blur, which through familiarity tends to be the standard against which other varieties can be compared. As we saw on the previous pages, focus blurring increases steadily according to the depth of the scene away from the point of focus. Most scenes shot at a wide aperture, therefore, contain many different degrees of ...