Body & Design
The 5D Mark III is very similar in size to its predecessor, but marks a distinct departure in layout from the previous models in the 5D line. It most closely resembles the EOS 7D, with its combined live view/movie control beside the viewfinder and power switch beneath the mode dial, but also borrows features from other recent Canon designs. So the 60D's mode dial lock reappears, along with the 1D X's little Q button between the joystick and rear dial. However there's further evolution of the EOS design that's entirely new to the 5D Mark III, including the repositioned depth of field preview button and revised playback controls.
The 5D Mark III's construction is excellent - it may not have quite the same level of disaster-proofing as the 1D X, but it certainly feels better-built and more substantial in your hand than the Mark II ever did. Perhaps the best way of describing this is that it's very much like the difference between the 50D and 7D - you wouldn't have said there was much wrong with the 50D in isolation, but the 7D is clearly better-built. The magnesium alloy shell certainly feels like it would come survive a pretty serious beating.
The top of the 5D Mark III resembles that of the EOS 7D, which means that the control set familiar to 5D Mark II owners is joined by an easily-reached customizable M-Fn button just behind the shutter release. The On/Off switch has migrated to a point where it's less easy to knock accidentally - but also less easy to reach when supporting a large lens with your left hand.
Top of camera controls (right)
The 5D Mark III's top controls will look immediately familiar to existing Canon owners. Behind the shutter release is the main control dial - this changes the primary exposure parameter, e.g. aperture in Av mode. Between the two is the customizable M-Fn button that can be set to operate functions such as Flash Exposure Lock.
Behind this is a row of three buttons which each activate two functions, changed using the front and rear dials. From left to right there's metering / white balance, AF / drive modes, and ISO / flash exposure compensation. The latter button is especially well-placed for changing ISO with the camera to your eye. Beside these is a smaller button that illuminates the top-plate LCD.
Top of camera controls (left)
On the other side of the pentaprism you'll find the power switch and mode dial. This has the familiar four exposure modes - Program, Aperture priority, Shutter Priority and Manual - plus Bulb shutter mode and three custom positions into which you can save camera settings for specific commonly-encountered scenarios. There's also the Auto+ mode previously seen on the EOS 600D that offers a range of results-orientated creative control - we can't imagine many 5D Mark III owners will use this much, but it does make the camera a bit more 'shareable' with non-experts.
At the bottom of the picture is the new image effects button that offers access to Picture Styles, multiple exposure mode and in-camera HDR. The latter is unusually well-designed - it saves all of the original files (not just the in-camera processed version), including RAWs. Unlike Canon's PowerShots, the 5D Mark III auto-aligns shots when processing, so you can shoot hand-held. There's also a range of processing 'looks' on offer, from 'Natural' through to, well, distinctly unnatural.
The rest of the 5D Mark III's major shooting controls are on the back, arranged for operation by your thumb. The combined Live View / Movie mode button comes from the 7D - if you flick the lever to the Movie position the camera enters live view with a 16:9 preview, so you can compose in the correct aspect ratio. Pressing the button at its centre then initiates recording. With the lever in the Stills position (as shown), pressing the button enters Live View.
The Q button brings up an interactive controls screen while shooting, that allows you to change camera parameters that can't necessarily be accessed directly through external buttons. It also brings overlaid option menus in Live View and Playback modes, offering rapid access to features such as in-camera RAW conversion.
The rest of the buttons and dials will be familiar to Mark II owners. The large rear dial sets exposure compensation in P, Av and Tv modes, and changes the aperture in Manual. The joystick is used to move the AF point around the frame, either in concert with the button on the top right corner, or if you prefer directly (via a menu setting). We think this makes much more sense for fluid shooting, but sadly you then end up with an entirely vestigial button which can't be customized to do something useful.
There are also three new buttons on the back of the 5D Mark III, including the mysteriously-marked 'Rate'. Here's an overview of what they do, from top to bottom:
|During stills shooting, gives direct access to Picture Style, Multiple Exposures, and in-camera HDR.
In playback, enters side-by-side image comparison mode. Here you can compare composition and focus of two versions of the same shot, compare histograms for exposure, or check sharpness of different areas of the same image.
|In playback, allows direct 'star' rating of images (1-5) in a format recognized by many image management programs, i.e., Adobe Photoshop Lightroom.
Can be reassigned to Protect/Deprotect images if you prefer.
|Magnify button - replaces zoom in / zoom out controls on camera's shoulder. In play mode, hold down and spin a dial to enlarge/reduce image.
In live view, cycles through full screen, 5x, and 10x views.