Sony makes a point of not calling this a 'professional' camera, instead referring to it as the 'flagship' model of its dSLR line. At around £2,000, it's priced like a professional model though, and its full-frame competitors -- the and the -- are widely, although not exclusively, used by professionals. Also, with such a high-resolution sensor, you need a really sharp, preferably fast lens, such as the that we tested it with; such lenses are expensive and generally out of reach for all but professionals.
Furthermore, Sony provides some of the most innovative and pro-friendly accessories we've seen, such as its sideways-rotating flash and , which almost exactly mimics the control layout of horizontal operation when shooting vertically. As with other Sony models, the A900 is compatible with Konica Minolta lenses.
A small status display on the top of the camera provides limited information -- shutter, aperture, battery and shots remaining -- while the rest of the information appears on the back LCD. Like the A700, the A900 lets you access and edit all of your settings directly via that display, which we liked.
The controls take a bit of getting used to, since many of them look and feel the same, making it hard to remember their locations. The A900 does provide three custom-setting slots on the mode dial, which is very useful, and the large, bright viewfinder is a pleasure to use.
The A900 has two design flaws, however, that may drive you insane.
Firstly, there's no way to lock the navigation joystick, which you use to shuffle around autofocus-point selection. If you always use the spot or wide AF, which don't move, it shouldn't bother you. But, if you use the local AF, as we did, the selected AF point frequently gets changed by accident.
Secondly, the preview button is also far too easy to trigger accidentally, and, when set for the 'Intelligent Preview', it switches the camera into a different mode, which you have to escape. Everyone we handed the camera to accidentally triggered it.
Also, while it's not really a design flaw, the A900's mirror is unusually loud.
Unlike its competitors, which use lens-based image-stabilisation systems, Sony has opted for in-body sensor-shift image stabilisation, now dubbed 'Super SteadyShot Inside'.
One of the A900's distinctive features is the aforementioned Intelligent Preview. Hitting the depth-of-field preview button shows a temporary capture of the scene on the LCD, where you can tweak parameters such as exposure, white balance, shutter speed, aperture and so on, and get a near-live preview of the changes. It's a good idea but, in practice, we found the LCD didn't represent the image accurately enough for us to make all but the most basic judgements.
The A900 also has the typical array of features you'd expect, including 'Creative Styles', for customising contrast, saturation, sharpness and brightness; 'Zone', which preserves highlight or shadow detail, depending on the setting; D-Range Optimizer (DRO) for expanding the dynamic range; and exposure (+/- 3 stops at 1/3 or 2/3 stop increments), white balance and DRO bracketing.
Some pro-orientated features include a compressed 'Raw' format that records 8-bit data instead of the standard 12-bit (you can read an in Dyxum.com's forum about the A700 if you're curious); the ability to fine-tune the AF to compensate for back- or front-focus problems (unlike Nikon and Canon's mid-range models, the A900 only supports a single setting); and the ability to customise the operation of the buttons and dials. You can for more details of its features and operation.
To support the huge bandwidth required by its large images, Sony supplies the A900 with not one but two of its Bionz image processors. That helps the A900 maintain its respectable burst rate of close to 5 frames per second (although, even with a fast UDMA memory card, such as the 4GB SanDisk Extreme Ducati, the buffer fills quickly) and keeps high-ISO shots from taking too long to process and save.