I have a 5D MK II, and had a 40D as backup. i decided to buy a 7D as a birding camera, but decided that it was too specialized and returned it and bought another used 40D. Then, I had a opportunity to buy a almost unused 1D MK III, so I bought it and sold the 40D.


It gets much more use than the 7D did, at a couple of hundred more than the 7d, I much prefer it.


As I see it, the advantage to me of the 1D MK IV is the high iso. When photographing rapidly moving objects, a fast shutter speed is better, 1/2000 sec is often ideal. That combined with a slightly stopped down aperture requires high ISO, so that would be a improvement. My 1D MK III can shoot at ISO 3200 with good results, but not 6400.


I would be able to use 6400 or maybe 12800 on a mark IV. That translates to smaller apertures and or higher shutter speeds and sharper images.