As one might justifiably expect from a camera costing well over £300, the T900's overall performance is excellent. It starts up in comfortably less than two seconds and shuts down again even more quickly. In single-shot mode the shot-to-shot time is approximately 1.7 seconds, which is nice and quick, while in continuous shooting mode it can rattle off 1.4 shots per second, which is exceptionally fast for a 21MP compact.
The T900 has an excellent nine-point autofocus system, and it is certainly one of the areas where your money goes. It is very fast and accurate, and will focus in any virtually lighting condition. The T900 has one of the brightest AF assist lamps I've ever seen, with a useful range of over five metres. The built-in flash is superb, easily filling a five-metre room, and operating outdoors at a range exceeding its claimed 4.5m maximum range. However it also works well at close range, illuminating subjects just a few centimetres in front of the lens without burning out highlights.
The one thing that could justify the T900's enormous price tag would be superior image quality. However while it is indeed very good it is not without its problems, and anyone who's read any of my previous reviews of 12MP ultra-compacts can probably guess what they are. The T900 has a tiny 1/2.3-inch sensor, and even though it uses Sony's Super HAD technology, with its larger photocells and micro-lenses, it's still trying to cram over 12 million of them into a space about as big as the word ‘big' appears on your screen. As a result the T900 suffers badly from image noise at higher ISO settings, and has limited dynamic range, although the DRO feature does go some way towards offsetting this. Images at 1600 and 3200 ISO are particularly bad, pixel-binned and interpolated to the point where there is almost no detail.
This is a pity, because apart from these flaws the camera produces excellent results. At ISO settings up to 200 the image quality is very good, with rich colours, smooth tonal variations and plenty of fine detail. As expected the Carl Zeiss lens is superb, with outstanding corner-to-corner sharpness with minimal wide-angle distortion or chromatic aberration. Image files average around 4.6MB, which is a little on the small side for a 12MP camera, but nonetheless images show no noticeable signs of compression. Flash and low-light images are particularly good, with accurate exposure and no red-eye.
There's no question that the Sony Cyber-shot T900 is a superb camera. It's very well made, looks good, and is easy to operate thanks to one of the few good touch-screen interfaces. It has a number of useful and entertaining features, outstandingly fast performance, and produces very good results, especially in low-light social situations. However it's not without some image quality issues, and it is ridiculously overpriced. It's good, it's just not that good.