Another trick with the gaussian filters and alphas is that you can blur something gradually - let's say you have a picture of a car, and the depth of field is really shallow, so just the front 1/8th or 1/4 is in focus. Let's assume the car is at a 45 degree angle from the camera, front of the car toward the left of the frame. The car is the selection, and you want to paste it into a CG background. The rear end of the car has a lot more blur to it than the front. Easy way to deal with this (or at least to create a quick n dirty fake) is to have your car alpha (once you've selected it), then create an all-new alpha channel. Do a black to white gradient from left to right (so black is left, white is at right). Make this alpha the selection, then make your active channel the car selection. Now you can apply a gaussian blur to the car alpha, and it will blur more pixels where your gradient alpha was white. If this makes no sense, I can do up a screen shot tut so you can see what I mean... .m