Depth of Field can be added to a scene by isolating and blurring only a portion of the image. The amount of blurring is directly proportionate to the luminance of the matte settings, a gradient or an input image.

Diffusion.

To select a preset, choose one from the Presets tab.

Selects the source for the selective blur effect.

Use a matte for the depth source.

Use a gradient for the depth source.

Use an image as the depth source. This is useful for 3D programs which render out depth mattes.

Sets how much the image is blurred.

Depth of Field can optionally use a gradient that limits where the node is applied. Grad is the transition area that goes from the blurred portion to the original image. Its direction, corners and size can be adjusted. Go to the Grad section of Common Node Controls to see how the Grad controls work.

A matte can be used to create the depth of field effect. Go to the Matte section of Common Node Controls to see how the Matte controls work.