PhotoShop in Action for your 3D Renders – 3ds max
Jelmer has made a very fine example how Photoshop can help you improve your 3d post render / editing work. Applying DOF and other effects can be acheived with Photoshop with simply export of Render Elements from 3ds max and can be used within Photoshop.
"First of all you can save yourself a lot of time, of course you can change the material settings again, or shift that background image but your last render might have taken hours already, you don’t want to wait that long again do you? Obviously this also makes editing in photoshop much more flexible, you can preview results within the blink of an eye and undo any changes you make. "