Alan - Eric offers excellent advice. Diffraction is usually the last factor reducing image sharpness and is frequently over ridden by other concerns, most often, poor technique(s). Removing all diffraction is meannigless if you don't have adequate DOF. Ny advice is to enjoy capturing meaningful images, enjoy a wonderful hobby and don't get wrapped around the axle on technical fine points. I hope you are as wowed by your D700 as i was with my first D700. Even though I have scrutinized opinios and other factors concerning the D800, I am not convibnced that for my work it brings anything that i NEED. And in fact, at this juncture I am most likely to grab a "low mileage" cherry D700 for a back-up to the two I already employ. And oh yes -- enjoy this wonderful forum for sharing ideas and methods, as I am sure you have for a decade now!