The A590's overall performance is well up to Canon's usual high standard. It starts up in less than two seconds and shuts down again almost as quickly. In single-shot mode it can take a picture every 1.5 seconds, while in continuous shooting mode it can zip along at 0.7 seconds per shot, a speed it can maintain until it either fills up the memory card or the batteries run out. Battery duration may be an issue however; Canon claims 200 shots on a set of standard alkaline batteries, but with a brand new set of Duracells I found the battery level indicator flashing red after only 120 shots. Perforamce using high-capacity NiMH rechargeables may be somewhat better though. The autofocus system is also just as fast as we've come to expect from Canon compacts, and for once the AiAF system appears to be less unpredictable, so it may have been tweaked slightly for this model.
In terms of image quality, I have to admit I am a bit disappointed, but largely because I have higher expectations of Canon compacts. The lens produces relatively little distortion, but it is only really sharp near the centre of the frame, with the edges exhibiting significant blurring and some chromatic aberration. The overall level of detail is about average for an 8-megapixel sensor, and dynamic range is also pretty good. However it does have a tendency to burn out highlights, and very bright colours also present a problem, with yellow and red flowers appearing as featureless blobs of colour with little visible detail. Image noise was also an unexpected problem, with noise plainly visible as low as 200 ISO and becoming a major problem at 800 ISO. Shots at the maximum 1600 ISO are virtually unusable. Considering the exceptionally good noise control of the A720, which has the same 8MP sensor and DIGIC III processor this is very puzzling, and a major disadvantage for an otherwise capable little camera.
Considering its low price, the PowerShot A590 IS offers an amazingly complete list of features, with high-performance optical image stabilisation, a useful range of manual controls and exceptionally good performance, especially in low light conditions. Build quality and handling are also well above the average for this price bracket. The only real disappointment is the slightly inferior image quality, especially when compared to the next model up in the range, the A720 IS. However for under £120 it is still a major bargain.