Key Technologies

The biggest single upgrade on the 5D Mark III is its autofocus system, and it's the area that most needed it. The original 5D's 9-point AF system seemed a little under-specced when it was launched, so its reappearance in the Mark II was a considerable disappointment, especially when the 7D arrived a year later with a much more sophisticated 19-point setup. The 5D Mark III's AF eclipses both, gaining the 61-point AF sensor from the company's flagship 1D X.

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It's not the entire 1D X AF system - because the 5D Mark III doesn't have the 1D X's 100,000 pixel metering sensor to gain tracking information from, nor a dedicated DIGIC 4 processor to make sense of it all. However, even without them, it's still one of the most comprehensive AF systems on the market and, most importantly, brings the camera much closer to the level of contemporary Nikons.

The 5D Mark III uses the same AF sensor as the more expensive EOS-1D X.
The 76 bright regions on the sensor are the light-sensitive areas.
Once focused through the lenses that are placed in front of them, their pattern relates more closely to the AF point pattern you see through the viewfinder.
And, if you overlay the AF point pattern, you can see how the 76 strips on the sensor give rise to the 61 selectable AF points.

It's worth bearing in mind though that, while Nikon has long used high pixel count metering sensors to improve tracking accuracy, the Canon EOS-1D Mark IV was competitive with the D3S even without this capability. Crucially, in addition to this added sophistication, the 5D Mark III also inherits the 1D X's subject-based configuration presets, to make it easier to get the best out of the system.

22MP image sensor and Digic 5+ processor

The pixel count may be similar to that of the 5D Mark II, but the Mark III's sensor is entirely new. The pixel architecture is changed, with a promised increase in photoelectric conversion rate (light is more efficiently converted to readable charge).Canon has also applied its gapless microlens array, meaning more of the light hitting the sensor gets directed down into the photodiodes. Finally there's a newly-developed on-chip noise reduction system to improve the quality of the information coming off the chip.

Image data captured on the 5D Mark III's 22Mp sensor is processed in the new Digic 5+ processor.

Canon isn't making specific claims for how much of an improvement these changes make to the raw output but, once subjected to the DIGIC 5+'s processing, it will claim a 2-stop improvement in the JPEG images.

The camera uses the latest DIGIC 5+ processor, as used in the 1D X. It's 30% faster than the DIGIC 5 chip starting to appear in recent Canon cameras but, more to the point, it's 17x faster than the DIGIC 4 processor in the 5D Mark II. This not only helps support the camera's 6 frame-per-second shooting but also has time on its hands to conduct moiré-reduction when shooting movies.

In addition, the extra processing power allows the 5D Mark III to apply chromatic aberration correction to its JPEGs. This correction is based on Canon-created lens profiles, up to 29 of which can be downloaded and saved onto the camera. These profiles allow correction not only of lateral CA but also of the harder-to-fix axial CA.

New shutter/mirror mechanism

The 5D Mark III features a totally redesigned shutter and mirror mechanism. The shutter is still rated to 150,000 cycles despite the faster continuous shooting speed. The camera also gains a revised mirror return mechanism designed to ensure the sub-mirror (that redirect light down to the AF sensor), is in place and stable as quickly as possible after each shot, to increase focus accuracy during continuous shooting mode.

The 5D Mark III also acquires the 1D X's silent shutter mode, allowing it to shoot in both single images and continuously (at around 3 frames per second) with greatly reduced shutter and mirror noise. This may not sound like much, but it should be very welcome to photographers shooting at noise-sensitive events.

Upgraded LCD Monitor

The rear screen is the same 3.2" 1,040,000 dot LCD as on the EOS-1D X. It's a 3:2 aspect ratio screen that uses the latest design in which the panel is bonded directly to the toughened glass screen, so that there's no air gap between the two (which could cause internal reflection - worsening glare). The result is one of the best screens currently available - clear, sharp and high-resolution.