Focus and Depth of Field

Overview

So far we have explored several different depth cues, such as size , occlusion , perspective, and light and shadow. In this chapter we'll turn our attention to the concepts of focus and depth of field. The notion of establishing depth in a scene has its origins in art, but the specific term depth of field has found broad usage in photography. Depth of field as defined in photography is the distance from the camera within which objects remain in focus.

One way of visualizing how depth of field works is to imagine a plane at some point in front of the camera where objects are perfectly in focus. As an object moves farther from this plane, it becomes less sharp. The rate at which this sharp to blurry transition occurs is determined by the aperture and speed of the camera's shutter. Photographers often use this effect to emphasize a certain part of a scene in a photograph. In cinematography, depth of field is often used to move the viewer's attention from one part of a scene to another.

Depth of field and focus are essentially depth-based camera artifacts that we can exploit to build more convincing 3D scenesso let's get started!