Well, to reduce the depth of field in post you'd have to use a sophisticated compositing software, and even with that, it wouldn't be genuine. Now, to reduce the depth of field while shooting, like with a DV cam, you need to utilize your zoom and manual focus controls. Example: If you're trying to get a close up, and want a reduduction in the depth of field, step back about five steps from your subject, then zoom and manually focus your subject into frame. That should give you the depth of field you desire.