"The Best Camera for Action Photography"4.5 starson by chasrob9945
Pros: Great Image Quality (even at high ISO), 10 FPS shooting, Extensive Custom Function Menus
Cons: Pretty complex for the less experienced
Summary: Afer reading some of the negative reviews on this site, I'm wondering how many people have really used this camera extensively and really understand the auto-focus complexities. I have owned this camera since July 2007, and have made over 6000 images with it since then, including over 3000 in warm weather in Kenya in August, and well over 1000 recently in cold weather in Bosque del Apache in New Mexico. The performance has been superb, all in all, considering the high demands I placed on it for photographing high speed chases (Cheetahs) and high speed flight (birds flyng directly toward the camera for landing at close range). Canon released a service advisory for an auto focus problem due to a sub-mirror assembly problem in some (but not all) Mark III's, and my serial number was among those listed as probably having the problem. I was too busy to send it in for repair until after I returned from Bosque, but I was very pleased with all the great images I brought back from Africa as well as Bosque. I recently purchased a Canon 40D as well, and flight shots at Bosque with both cameras showed a higher percentage of perfect focus with the Mark III than with the 40D. By the way, I finally sent the Mark III off for repair two weeks ago on a Friday, and had it back in my hands the following Friday, with an extended warranty of a year from the repair date (on the whole camera, not just the repair).
There are custom functions that affect auto-focus performance on this camera that simply do not exist on other cameras, including the 40D, so that adds to complexity and the possiblity that the camera may not be set up optimally for the kind of shooting you are doing. However, once you have it set up properly, I believe you will be struck by some of the awesome images you can make. I know a number of professional photographers who are shooting with this camera almost exclusively, and I'll always choose it over the 40D for the most difficult shooting situations.
By the way, I have a leopard image from Kenya made after sunset at ISO 3200, 1/60 second, that is virtually noiseless. My 40D at the same shooting conditions in Bosque couldn't come close, with a fair amount of shadow noise present.