Pat, I'd love a 1DX... but my wallet can't take it, unless you're feeling really, really generous. But, I'm curious how the 1DX would handle an agility event.

Depending on your framing your meter can do very odd things. If the dog doesn't fill the majority of the frame, the exposure is based on a lot of background. A black dog loses detail, which on a crop body isn't very recoverable. A white dog clips to unrecoverable super-white levels. A black and white dog in a mix of full sun on it's back and shadows below clips on both ends of the histogram at once!

You can throw on some EC (I have EC tied to the AF-mode switch lever thingy so I have fast access to it), but if the black dog starts filling the frame, you start getting a very bright black dog and clipped surroundings. If a white dogs start filling the frame, you start to get a very dim grey dog and blackened surroundings.

In the end I tend to just set everything manually, and do a slight + or - adjustment between dogs, based on the brightness of the last image, and the color difference between the two dogs. I do get it wrong sometimes, and add in mid-run light changes due to clouds, and I definitely miss shots that should be awesome, but I lose less this way than using the meter.

The 1Ds2 had an interesting difference from the 7D bodies. It seemed to understand highlights. It would expose such that highlights wouldn't clip, or not much. In an image with a bright reflection or highlight, it would underexpose, which, on a more modern full-frame sensor you could bring the shadows up and recover that detail. A 1DX, if it behaves the same way, would be nice... It's like an over-exposure safety-net. If the 5DIV behaves the same, AND you get its improved dynamic range and shadow-boost capabilities along with highlight smarts in the meter, that would be a killer combo. But, I'm guessing the highlight thing is 1D specific. I heard (so could be wrong), that the 1D series does the gain processing in analog, while every other body does it digitally. It could be that the 1D analog circuitry can detect the highlight and compensate in ways that the other camera can't.

Brant, I would say that wasn't a fair test of the AF. People will blur at 1/100. A fast dog stands no chance. Typically for a fast running dog, we aim for 1/1600s as a minimum. If the dog is running sideways across the frame, you'd best be panning to match them, too. This shot is at 1/1600s (85mm, but AF isn't taxed because it is sideways action, not front/back). I was panning to match Zuni. Note the level of blur on the grass and hind leg. If I weren't panning, Zuni would be as blurry as that grass... Potentially more, as the dog's leg moving forward is moving faster than the dog as a whole, and would would blur more.


Zuni running for a ball by Dave E, on Flickr