Z-buffer channel

Outputs an image representing scene depth within the two values specified in the Z-buffer range. The range is in meters.The darker the object in the Z-buffer, the farther away from the camera it is. This channel is useful to create a depth of field effect as a post process in an image editor that can use a Z-buffer image to extract depth info.

For common usage, you should specify the range from the camera to the farthest object in your scene. If you specify a too wide range, or too narrow, the Z-buffer will not represent accurately the scene depth.