how to create DOF in photoshop

hi ^^
i'm going to show you how to create DOF (depth of field) in photoshop, it's very easy, we're going to use a mask.
1.-open your pic in photoshop

2.-select this tool (edit in quick mask mode)
3.- we're going to use the gradient now, your pic should look like this:
4.-repeat step 2 and now a selection will appear, go to "filter->blur->gaussian blur" and change the radius until you get the effect you like and that's it!
easy right?