Quote Originally Posted by Legion5


As btaylor said f/4.0 is an very narrow DOF and is often capable of cutting someone's body or face in half when taking up most of the frame, f/2.8 is even narrower.



Yes, the DoF is thin. But, if you compare the DoF at 200mm f/2.8 with a similarly-framed shot at 85mm f/1.2 (closer to the subject, obviously), the DoF at 85mm f/1.2 is less than half of that at 200mm f/2.8. The EF 85mm f/1.2L II is Canon's quintessential portrait lens. Granted, not all portraits are shot at f/1.2. But sometimes, that's the effect you want...and while you can stop down the 70-200mm f/2.8 for more DoF, you cannot open up the 70-200mm f/4 any wider than f/4 if you want the DoF to be shallower.