This tutorial shows how to decrease the depth of focus in an image as if the photo was made with a large aperture. The effect will isolate the subject from the background and will draw the attention of the viewer to the actual subject of the photo. [details (http://www.retouchpro.com/tutorials/index.php?m=show&id=10)]

A quibble, an extension, and a caveat.

Quibble: Depth of Field is what is being changed. Depth of focus is an internal effect in the camera relating to film/sensor location. They sound like, but are not the same.

Extension: Before blurring the part to make "out of focus", delete the main subject from that layer. If this is not done, the blurred layer can create "blur halos" around where the subject was, extending the pixels of the subject onto the background. This gives a very odd appearance.

Caveat: This technique is best used with fairly small blurring amounts and with images with consistent depth to the background. Otherwise, the effect is easily spotted and will reduce the believability of the scene. (Sometimes just blurring the foreground is safer, as that usually is planar to the gradient's direction.)