i play with DOF from time to time even though i've only got 1 lens and no training. with an 18-55 i position myself, crank the barrel to 5.6 and frame up. there is probably an easier way and i'm sure if i had a 200 or 300 i could stand a distance away for the same and better effect but i'm learning. it is a fun tool to play with. i wouldn't make every pic in your shoot like that, just as i wouldn't dutch angle an entire video
