On depth of field - don't forget that DOF works as a percentage (sort of) of distance from the subject. With a 50mm lens at f/4 and 1 foot you may have a DOF of under 1/16 inch. But at f/4 and 10 feet that becomes 2 feet.
An online DOF calculator is at:
http://www.dofmaster.com/dofjs.html