I am looking for some lens info. My wife is looking for a "Portrait" lens. She does wedding photography and likes to blur the background. I assume a portrait lens would be in the 100mm size for our Nikon camera, however I'm not sure this lens will do what she wants. I am of the opinion that any lens (regardless of maximum aperture) will have the same amount of DOF as long as they are of the same focal length. I was always taught that DOF is caused by the light bending around the leaves of the aperture as you stop down, so would a 100mm 2.0 have the same DOF as a 18-105 4.5, as long as both are open to the maximum? Hope you can shed some light on this for us!