The 7-megapixel camera's tiny body is shiny, curvy and very attractive. But it may be too stylish for its own good. For instance, the power button is a tiny, illuminated half-oval built flush into the top panel -- without actually pressing it, you might easily mistake it for an indicator light or a design flaw.
The IXUS 850 IS's most prominent feature is its image-stabilised, f/2.8-to-f/5.8, 28mm-to-105mm-equivalent lens. The 3.8x zoom range offers the flexibility of wide-angle focal lengths, while still providing more zoom power than the average 3x point-and-shoot lens. Though the 800 IS had a 4x zoom lens, the 850 IS's 28mm-equivalent wide shot more than makes up for the slightly smaller telephoto factor.
In addition to the flexible lens, the 850 IS has some handy snapshot features. The camera's sensor can be boosted to as high as ISO 1,600 for low-light or high-movement shots, though you'll want to keep it at ISO 800 or lower because of image noise. You can shoot 30fps VGA video, or bump it up to 60fps QVGA (320x240-pixel) resolution to capture action footage for half-speed playback. If you're looking for manual controls, however, look elsewhere -- like the 800, the 850's aperture and shutter settings can't be changed at all, its focus modes are all automatic, and the camera's manual mode allows only exposure compensation, colour correction, metering and white-balance adjustments.
The IXUS 850 IS also uses the recent Digic III image processor, which Canon claims improves image quality, performance and battery life. We didn't notice any significant improvements over the 800's already good performance, but the 850 seemed slightly more responsive than its predecessor. It performed excellently in our tests.