The Sony Alpha A900 is a late entrant to the DSLR market but it's wasted no time in making its mark.

It has three APS-C sized DSLRs straddling the low-end to enthusiasts market, and now its fullframe A900 goes head-to-head against pro models from Nikon and Canon.

Powerful pixel count

Sony's clearly proud of the A900's technology, citing the fact that it's the world's first 24.6-megapixel full-frame DSLR. It's a narrow margin, though. The EOS 1Ds Mk III has 21MP as does the new EOS 5D Mk II. Nikon can't compete on numbers at the moment – both the D700 and the D3 have just 12MP.

But let's get this in perspective. Twelve million pixels? How many, exactly, do you need? In theory, the Sony offers twice the resolution of the Nikons and fractionally more than the Canons, but at this level, even with a full-frame sensor, makers are facing diminishing returns. More pixels don't necessarily mean more definition.

The quality of the lenses available inevitably plays a part, and both Canon and Nikon have a long and established heritage in pro-quality lenses. Sony's lens range is building steadily, but it's still some way behind.

Pro standards

Both inside and outside the camera there are many indications that Sony's intent on producing a fully professional DSLR and not just a scaled-up version of one of its APS-C cameras.

The body's made using magnesium panels fixed to an aluminium alloy chassis, and it's dust and moisture sealed against hostile environments. Image quality on this camera is excellent and we couldn't find a single fault with the exposure system.

The viewfinder is big, bright and superbly clear, a by-product of the larger mirror/pentaprism assembly, and the shutter has a heavy but well-damped action.

If you don't like the focussing screen you can swap it, choosing between an L-type (grid) and M-type 'super-spherical acute matte' screen, and the InfoLithium battery gives an indication of the charge remaining as a percentage and should last for an impressive 880 shots between charges.

Steadier shots

However, Sony hasn't quite reached the same levels of finish and design as Nikon and Canon, even with the A900. The main mode dial has a rather plain, crude look, the top LCD panel is small and displays only basic exposure and shooting information, and the control labels use an untidy mixture of typeface and icon sizes.

It's also yet to match the smooth, near-silent AF systems employed by Canon and Nikon, and the A900 starts up with the same curious 'shunting' sound as the cheaper SLRs in the range. This, presumably, is due to Sony's combined dust removal and anti-shake system.

The anti-shake has been rebranded here as SteadyShot INSIDE. This is the only full-frame DSLR with integrated anti-shake, remember. It should work with newer Sony lenses and older Konica Minolta lenses too.

There are things the A900 doesn't have, though. There's no Live View and, as a result, there's no movie mode either, which the new 5D Mk II does boast, and in glorious 1920x1080 pixel high-definition, too.

Mega performance difference?

The big question, though, is whether the A900 can translate its megapixel rating into increased real-world definition. Certainly it's possible to see a difference between the Sony's detail and that of the D700, but your picture-taking technique has to be perfect.

Between the A900 and the EOS 1Ds MkIII (the only Canon available for comparison), it's closer still. The Sony is maybe a little better at rendering textural detail, but this is a long-standing weakness of Canon JPEGs. Shoot RAW and really there's nothing in it.