Canon’s revamped the Mark IV’s 45-point autofocus system to make it more precise than its predecessor. In our testing, the upgraded AF was quick and reliable.

Canon has a lot riding on its new fast-shooting EOS-1D Mark IV digital SLR. With Nikon barking at its heels in both the professional and consumer digital camera markets, and several sidelines of sports photographers eagerly waiting to see how Canon's follow-up to its less-than-well-received (to put it mildly) 1D Mark III will perform, the 16-megapixel Mark IV has been met with an almost unfair mix of anticipation and skepticism.

Most of the controversy over the Mark IV's predecessor swirled around its 45-point autofocus system which, at the time it was released in 2007, was being hailed by Canon as "a complete reconsideration of professional AF." It may have been, but it didn't necessarily please pros.

For the record, at the time I reviewed the 1D Mark III in these pages in August '07, I could find nothing wrong with the camera's AF system and, in fact, saw it as an improvement over the previous model. But such is the life of the camera reviewer. When you can only look at a piece of gear for, at the maximum, a month at a time it's hard to see how certain features evolve—or, in this case, devolve—over time.

And, without doubt, many pros found the 1D Mark III's AF system to be seriously flawed even after several attempts by Canon to fix the firmware and hardware in the cameras. One sports photographer even recently called the 1D Mark III "the biggest lemon" in modern professional photographic history. A pretty bold statement but if you polled sports photographers you'd probably find a lot of agreement with that assessment.

But that's the past. Now we have the Canon EOS-1D Mark IV with the unsurprising bump up in resolution (from 10 megapixels to 16 megapixels); a new 1080p, High Definition movie feature; the same lightning fast 10 frames per second shooting speed; and, yes, a revamped autofocus system which Canon hopes will make photographers forget all about the much-maligned Mark III.

But will they put it behind them after plunking down $5,000 on the new model? Let's take a look.