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.

And to put the megapixel difference in perspective, the Sony's 17 per cent resolution advantage over the Canon equates to a tiny eight per cent increase in image width and height (in pixels).

Fantastic lens

Lens-wise, it's hard to say how the Sony range is going to shape up, though the Carl Zeiss 135mm f/1.8 we also got to try out with this camera is terrific.

But with full-frame SLRs, unless the lens you use is first-rate, you'll be no better off than if you use an APS-C sized camera. The other point is there's a lot less depth of field when you go full-frame, so getting better results also depends on perfect shooting technique.

Resolution is only a small part of overall image quality, of course. Lens performance is critical at this level, as is the camera's colour and tonal reproduction and its noise/ISO performance. The A900 does a great job here.

As with the smaller Sonys, the A900 delivers nice, punchy contrast, excellent colours and saturation and very good exposures. It does get noisier at higher ISOs and it can't match the Nikon D700 in this respect, but it's fine up to ISO 1600.

The quality does drop off at ISO 3200, and ISO 6400 is probably a step too far for most, but it's still not a bad performance for a camera with such a high pixel density.

Squaring up to the competition

The A900 delivers great-looking pictures with the potential for very high resolution. But good as it is, there are still a couple of quibbles. The first is the price.

It'll cost roughly the same as the Nikon D700 and the Canon EOS 5D Mk II, but it's not quite in the same league for finish and finesse.

The second is the lens range, and it's going to take a little while to find out whether Sony really can square up to Nikon and Canon in the professional market.

Via PhotoRadar