The D810 has a 51 point AF system compared to the 61 point system in the Canon 5D Mark III, but it copes admirably with tricky focussing situations. Indeed, both the AF and metering systems are identical to those in the Nikon D4s, but at a much lower price. Considering its massive resolution and advanced features, the D810 is reasonably light and the pop-up flash is a useful bonus.
Canon EOS 1DX
Sensor size: Full frame Pixel count: 18.1Mp Screen type: 3-2 inch fixed LCD, 1,040,000 dots Maximum continuous shooting rate: 12fps Maximum video resolution: 1080p
Read our full Canon EOS-1Dx review
The 1DX is an amalgamation of the Canon 1D and 1Ds models, and a big selling point of this pro-spec model is speed – the camera boasts a 12 frames per second burst mode, which can be expanded to to 14fps in the Super High Speed Shooting Mode.
When the 1DX was launched, there were concerns that the 18.1Mp full frame sensor was a step backwards from the 21.1Mp chip inside the 1Ds Mark III, but Canon's rationale was that the lower pixel count would mean better image quality at higher ISO settings. Certainly, the sensor and dual Digic 5+ processor combination deliver detailed, clean images right through the sensitivity range, and the 1DX's maximum extended ISO setting of 204,800 set a new benchmark for pro cameras.
The 1DX also offers a comprehensive 61-point AF system. Add a fast lens and you'll be delighted by the 1DX's ability to focus even in tricky, low-light conditions.
The 1DX feels very comfortable and well balanced in the hand, too. This said, the 1DX lacks some of the practical touches of the 5D Mark III, principally the in-camera HDR system and image rating system. If you can live without these extras, the 1DX is a great choice for photojournalists and sports photographers.
Sensor size: Full frame Pixel count: 16.2 Mp Screen type: 3.2-inch fixed LCD, 921,000 dots Maximum continuous shooting rate: 11fps Maximum video resolution: 1080p
Read our full Nikon D4S review
This is a relatively minor upgrade from the fast, pro-spec D4, with improvements centring on better performance at higher ISO. Indeed, the D4S has an ISO range that stretches to 409,600 in expanded range, making this a real 'see in the dark' camera (although image degradation is very noticeable at this level).
As with Canon's 1DX, the D4S' pixel count is relatively low at 16.2Mp, less than half that of the cheaper Nikon D800. Nikon claims that the lower pixel count reduces noise at very high ISO settings and enables a faster continuous shooting rate – in this case, a nippy 11 frames per second, with the ability to focus and meter between shots.
The AF system is fast and comprehensive, with a new Group-area AF mode for keeping moving subjects sharp.
The D4S is built for speed, so if you need very high resolution images, the 36Mp D800 is a more logical choice. The D4S is big and bulky too, and the lack of built-in WiFi or GPS is disappointing in such a premium-priced camera.
Sony Alpha a99
Sensor size: Full frame Pixel count: 24.3 Mp Screen type: 3-inch adjustable TFT, 1,228,800 dots Maximum continuous shooting rate: 6fps Maximum video resolution: 1080p
Read our full Sony Alpha 99 review
The first full-frame interchangeable lens camera with an electronic viewfinder (EVF), the a99 also features a versatile articulating rear screen. The camera is based on a 24.3Mp sensor that delivers plenty of resolution.
You can also use Sony DT lenses designed for its APS-C format SLT (Single Lens Translucent) and SLR cameras, as the a99 will automatically crop to the smaller frame. There is more cutting-edge technology in the a99, including two AF sensors, one above the mirror-box with 19 AF points (11-cross type) and the other with 102 points over the actual sensor. The camera has a built-in GPS receiver too.
In practice, the a99 performs well, though the AF system struggles to keep up with the competition – the non-cross type AF points struggle in poorer light, and even with a high-quality lens, you'll have to tolerate some 'hunting'. What's more, the selectable AF points are clustered around the centre of the frame, forcing you to rely on the focus lock and recompose technique.
These AF limitations, combined with the lack of an optical viewfinder, will be a deal breaker for many enthusiasts and semi pros, which is a shame, as the a99 has many virtues and useful extras.