DOF = Depth of field. It means a field of distance that is in focus. Typically in a vue render everything from the nearest object to infinity is perfectly focused. This wouldn't normally happen in a real camera lens, so vue lets you simulate the effect of a real lens by having areas thrown out of focus. The instructions on how to use this effect are on pg63 of the manual, and as the manual goes arn't too bad. If you need any help just holla