The Good The Canon EOS 5D Mark III offers a more streamlined shooting design, significantly updated feature set with more configurability, plus better performance over its predecessor. It maintains its excellent photo and video quality as well.
The Bad JPEG photos at low ISO sensitivities don't match the generally excellent level of quality that you can otherwise get out of this camera.
The Bottom Line While it's not a no-brainer upgrade over the Mark II, the Canon EOS 5D Mark III is worth the price premium if better performance and configurability matter to you.
Canon EOS 5D Mark III
On the 25th anniversary of its EOS system, Canon finally announced the long-awaited update to its full-frame 5D Mark II dSLR. The 5D Mark III is packed with capabilities for both still and video shooters, but at a much steeper price. As you'd expect, the 5DM3 consists of a combination of technologies, features, and design updates rolled out in the EOS 7D and the more recent 1D X. The result is a camera that looks similar to its predecessor with a lot more capabilities and better performance, but isn't as different when it comes to the basics -- photo and video quality -- as you'd expect. Of course, the 5D Mark II is pretty great in those respects, so no drastic change isn't necessarily a bad thing.
Though a different sensor than that of the 1D X, it uses a lot of the same technology that Canon rolled out for that model, including gapless microlenses and improved quantum efficiency (to improve the amount of light capturable on the photodiodes); better on-chip noise reduction; and faster data readout (dual four-channel readouts). Though it has 6.25-micron sites compared with 6.4 microns on the older sensor, Canon claims that all the other advances, including the better processing in the Digic 5+ engine, delivers overall better noise performance -- two stops better for JPEG and video. Canon does say the 1D X remains about one stop cleaner, however.
There's no doubt that the 5DM3 delivers excellent photo quality. The unprocessed images do seem to have less pronounced color noise than the 5DM2, and at midrange-to-high ISO sensitivities the JPEGs do look a little cleaner. But at low-to-middle ISO sensitivities I actually think the JPEG photos from the 5DM2 look a little better, with more naturally defined detail and fewer processing artifacts. That said, the 5DM3's JPEGs do look fine up through ISO 1600, and depending upon the scene and your needs they can be quite good through ISO 6400. Raw images look great and unambiguously better through ISO 1600, though.