Fortunately, Digital IXUS and PowerShot models allow you to do so easily. Many of these cameras even offer two ways to achieve better results in the snow. The first of these is to switch to spot metering (see your manual under "switching
between the light metering modes"). This means that the light meter will only consider a very small area at the centre of the image (marked in the view finder), which you can aim at your subject (e.g. face). Press the shutter release half way, and then
compose your shot. The exposure setting will not change (and nor will the focus, for that matter) as long as you keep the button half pressed.
The second, and perhaps easier method, for obtaining correct exposure in the snow is to utilise the ‘snow’ special scene mode. In this instance, simply select the ‘snow’ preset and take your photograph. The snow setting is optimised so that subjects
are not underexposed, and the blueish tone that can often appear in snow photographs is eliminated.