I shoot both and depending on the situation the D800 is usually set to 2x the focal length due to those 36mp. The D4 is a little more forgiving coupled with the high iso performance. But we are comparing apples and oranges. The D4 is primary for wedding duties while the D800 is backup and for capturing detail & macro work. Don't know if I answered your questions but again, these are two different monsters that requires great technique.