Compared to the sleek elegance of Canon's IXUS ultra-compacts or the chunky ruggedness of the G11, the body design of the S90 looks surprisingly plain. The shape is a simple rectangular box with rounded ends and no handgrip or other protrusions on the flat front panel, and with only a small token thumb rest on the back. As we've come to expect from Canon the build quality is very good, but surprisingly the top and bottom panels are plastic, not something I'd expect from a £400 camera.
Fitting a full set of manual exposure controls onto a small compact camera is bound to present a challenge, but Canon's designers are a pretty inventive bunch. The S90 has an unusual rotating bezel control around the lens which is used to adjust various parameters. In manual and aperture priority modes it adjusts aperture, while in shutter priority mode it adjusts shutter speed. In auto and program modes its default setting is ISO adjustment, but it can be customised to adjust one of list of other parameters. It's a novel idea and might appeal to owners of older SLRs and rangefinder cameras, but to be honest I found it slightly awkward to handle, and the changing function depending on the shooting mode was somewhat confusing.
The S90 also has a rotating bezel control around the D-pad, something of a signature for the S series. I've never been a big fan of this type of control; some are better than others, but I'm afraid this one is just awful. It rotates far too freely with even the lightest touch and is very easy to jog accidentally while shooting. Since it controls exposure compensation in most shooting modes this results in many badly exposed shots. Just stiffening it up a bit or adding a 'click' to the action would have helped a lot.
Thankfully the rest of the controls are very good, with nice tactile feedback, and include a function button which can be customised to control one of a long list of options. The zoom control is the usual rotating switch around the shutter buttons, and although the zoom action is stepped it has eight increments between minimum and maximum so it's not too hard to get the setting you want.
The S90 is almost unique among recent compact cameras in that it doesn't have HD video recording. The video mode is limited to 640 x 480 resolution at 30fps, with mono audio recorded via an internal microphone. The optical zoom cannot be used while recording, but there is a smooth digital zoom available. The video and sound quality aren't that brilliant by recent standards, but at least it can record clips up to an hour long.
The S90 does offer a wider range of control than most other compact cameras, with features such as tunable automatic white balance, exposure and focus bracketing and stepped zoom settings to particular focal lengths. The usual My Colours feature allows five-step customisation of contrast, sharpness, saturation, colour balance and skin tone. While by no means a replacement for a digital SLR it comes close to the versatility of the PowerShot G11 but in a much more compact shape, although I have little doubt that the first comment following this review will be someone complaining about the lack of an optical viewfinder.