The circle of confusion

The circle of confusion is a technical term used quite often in photography. It’s related to how your lens focuses as well as the aperture value that you use to shoot your images. It also influences depth of field, as well as how some lenses tend to produce softer images than others.

UNDERSTANDING LIGHT

To understand the circle of confusion we need to understand how light travels from a point source, through the lens’s many elements and then goes on to hit the sensor inside the camera. Light originating from a point source hits the lens’s front element. Now, there are many elements inside the lens but the one that really matters for this discussion is the focus element.

WHAT IS THE CIRCLE OF CONFUSION?

When the focus point and the focal plane do not meet, a point source of light (a round light source) appears slightly bigger and no longer appears to be in sharp focus. However, there is a certain range of tolerance in front of and behind a subject before it starts to appear out of focus to the human eye; that range is what is known as circle of confusion.