Coming in near the top end of Canon’s huge range of digital compacts, the 850 IS (update to the 800 IS) has many interesting features. First, is its optical image stabilisation. Canon’s claims that it allows a two-stop decrease in shutter speed are pretty accurate — if you could previously hold the camera steady down to 1/60th of a second, you can now get a sharp shot at 1/15th. There’s also an extension to the AiAF auto-focus system — a face-detect mode. Switch it on and the auto-focus indicator box uncannily locks onto and tracks faces in the shot. As a result, it’s almost impossible to get portraits out of focus.

The body is much the same as the Ixus 65, with just a couple of millimetres added to the thickness. Unlike the 65, you get a small optical viewfinder, which means the LCD screen is a little smaller at 2.5in. It’s as bright and clear as we’ve come to expect from Canon, though, and the image playback — complete with slideshow option offering selectable transition effects — is superb.

In keeping with a general trend towards offering high-sensitivity modes, 
the 850 goes up to ISO 1600. But this produces an enormous amount of image noise and we judged it to be unusable. ISO 400 is the limit we’d be happy with.

The final headline feature is the lens. As far as the zoom range goes, it’s a standard 3x, but at the wide-angle end you get a 28mm equivalent focal length. This allows for some wide-angle effects with exaggerated perspective.

The problem is that the quality of the lens isn’t as high as we’d like, with exaggerated chromatic aberrations more reminiscent of the results from a two-year old camera than one near the top of Canon’s current range. There are also some pronounced blooming effects around image highlights. On top of this, the in-camera JPEG processing appears less than top-notch, possibly as a result of over-sharpening to compensate for lens softness, giving salt-and-pepper noise and loss of detail. The overall effect is image quality a little below that of the Ixus 65, which is disappointing.

While we’re impressed by such innovative features on a digital compact, the image quality largely negates them. The net result is a camera that’s superb as a feature-laden gadget for the casual snapper, but will likely disappoint the serious amateur who wants a backup for their digital SLR.