One of the A900's main selling points is its high-speed performance, provided by dual Bionz image processors and on-chip parallel A/D conversion. In all shooting modes including uncompressed Raw + JPEG it can shoot at a blistering five frames a second, which is crucially one frame per second faster than the EOS-5D MkII. The image buffer is large enough for only 10 frames in both of the Raw + JPEG modes and 11 frames in Extra Fine JPEG mode, but in Fine JPEG it shoots up to 105 frames before pausing, which is pretty impressive.
The A900 has a new autofocus system featuring nine AF points including a dual-cross centre spot and an additional 10 "autofocus assist" sensors, which apparently help to detect lack of focus and reduce focusing time. As a result the AF system is exceptionally fast and very accurate. Unusually for a DSLR the A900 is equipped with a very bright and highly focused AF assist lamp that projects a pattern of lines onto subjects in low light conditions, enabling it to focus in total darkness at a range of several metres, but even without this feature its low-light focusing is very good.
One of the biggest advantages of a full-frame DSLR is that the huge sensor allows much bigger photocells, with correspondingly greater light-gathering capability, which in turn means greater colour depth, wider dynamic range and less image noise. Of course cramming on more photocells does counteract this to some extent, but the 35.9 x 24mm sensor is so big that even with a 24.6 million photocells the size of the individual sensor cells is still larger than those of the A700.
I've already praised the A900's excellent dynamic range, and in terms of sheer detail there's no question that it can out-perform anything else on the market, short of a medium-format studio camera. Combined with the outstanding Carl Zeiss T* 24-70 f/2.8 lens the A900 produces noticeably finer detail and richer colours than the Canon EOS 5D MkII, although how it fares against the Nikon D700 I'll have to wait and see.
The only criticism that can really be laid against it is that at higher ISO settings in JPEG mode with the default noise reduction settings, the images are a little noisy over 800 ISO. Hoever at lower settings, and especially when shooting in Raw mode and processing the images in Adobe Camera Raw, the preferred workflow of most professional and enthusiast photographers, the A900 produces some of the best images I've yet seen from a digital camera. Turn to the sample shots on the following pages to see some of the results I've managed to get from it.
The Sony Alpha A900 is an immensely impressive camera, equalling or surpassing its few rivals in almost every criterion with a combination of superb build quality, blistering performance and class-leading image quality. It would suit any advanced enthusiast or a professional who wants a lighter alternative to a D3x or EOS-1D.