Kyle, the difference between the 1D and the 1DmII is fairly significant in terms of IQ and powerhandling. The mII is the superior camera, though it lacks some useful modern features (tiny LCD, no live view, no self-cleaning sensor, big heavy batteries, limited ISO range). It is a great sports camera and built like a tank. That said, low milage copies are getting harder and harder to find. In comparison, the 40D has more MPs on a smaller sensor, but the greater pixel density is well controlled and noise isn't an issue up to ISO 1600. It has live view and the self-cleaning sensor, a larger LCD but not high-res, and great IQ. The viewfinder is exceptionally bright given the smaller sensor and mirror. The focus is not 1D series by any stretch, but it's better than people make it sound in the Canon forum. The 40D can take more alt lenses without modification thanks to the small mirror. The 50D was a minimal upgrade by most accounts, but I don't have enough experience with it to form an opinion.
carstenw wrote:
Ring USM is about noise, not speed. Some cameras, like the Sony A900, don't have USM in many of their lenses, yet focus blazingly fast.
While I have not tried the A900, ring USM is definitely about speed. I used may lenses with ring USM, micro USM and AFD. All other things being equal, ring USM is faster, sometimes much faster. Moreover, it also compensate for slower aperture.
