A Basic Guide to Circle of Confusion in Photography

When you enlarge a photograph beyond a certain size, you may notice that parts of the photo that once appeared sharp now seem blurry. In fact, the larger the print size, the more blur the human eye can perceive. This phenomenon varies depending on viewing distance, image size, and the sensor size of the camera that took the photo. Because camera lenses cannot achieve absolutely perfect focus, even the smallest dots in an image are actually blurs of light that your eyes perceive as dots. Photographers refer to the measurement of such optical blurs as the circle of confusion.