White Balance

The SD400 has five white balance presets (daylight, cloudy, incandescent, fluorescent, fluorescent H) in addition to the default auto white balance. There is also a 'custom' white balance setting, which allows you to point the camera at a white or gray object and set the white balance manually. The custom white balance setting is remembered even if you turn the camera off. In normal outdoor shooting the auto white balance works perfectly (as confirmed by our studio tests). Indoors it's a bit more hit and miss, as we've seen with most Canon PowerShots, fluorescent lighting doesn't cause much of a problem, whereas incandescent (tungsten) lighting causes a fairly strong orange color cast. Best to stick to the preset (or one-push custom WB) if you want more neutral colors. We've spoken to Canon about their approach to white balance and have been told that the warm colors we see when shooting under incandescent light are intentional and are intended to 'try to keep some of the warm atmosphere of this kind of shot'.

Outdoor - Auto WB
Red -1.7%, Blue 0.0%

Fluorescent - Auto WB
Red -0.2%, Blue 0.0%
Incandescent - Auto WB
Red 10.7%, Blue -20.7%

Flash Performance

The SD400's built-in flash has a quoted working range of 0.5m - 3.5m (1.6 - 11.5 ft) at the wide end of the zoom and 0.5m - 2.0m (1.6 - 6.6 ft) at the tele end. It also works down to about 30cm (12 inches) in macro mode (in all cases assuming the ISO is set to auto). In our real-world tests the flash did a fantastic job, exposing perfectly in a wide range of situations and with virtually no color cast. It's also pretty fast - even with the red-eye reduction turned on, meaning you won't miss any spur of the moment shots waiting for the flash. In fact - as long as you remember the range limitations of the flash you'll find this the perfect 'social' snapshot camera. We found the AF illuminator would allow focus in complete darkness (or as near as we can get) at distances of up to around 1.0m. In low light the AF illuminator can help focus at distances of up to around 1.8m.

Skin tone
Excellent color and exposure
Color chart
Excellent color and exposure

Macro Focus

As is common to most compact digital cameras the SD400's macro mode is most effective at the wide end of the zoom, where you can get as close as 3cm - unusually close for an ultra-compact. At the long end of the zoom the performance is less impressive - 30cm subject distance - but still pretty useful. There is inevitably some distortion when shooting very close up at the wide end, but it is not too strong, and certainly less so than many of its competitors.

Wide macro - 55 x 41mm coverage
41 px/mm (1041 px/in)
Distortion: Average
Corner softness: Low to average
Equiv. focal length: 35 mm
Tele macro - 90 x 67 mm coverage
25 px/mm (638 px/in)
Distortion: Average
Corner softness: Low to average
Equiv. focal length: 105 mm

Barrel and Pincushion Distortion

Barrel distortion is - at 0.7% - very low for a camera in this class, and certainly doesn't mar real world scenic shots. There is only the tiniest measurable distortion at the telephoto end of the zoom. We did notice a tiny amount of vignetting (darkening of the corners of the frame) at the widest zoom setting, but didn't see this in real world shots.

Barrel distortion - 0.7% at Wide angle
Equiv. focal length: 35 mm
Pincushion distortion - 0.7% at Telephoto
Equiv. focal length: 105 mm

Noise Comparison

Here for visual comparison are four identical shots taken at 50, 100, 200 and 400 ISO settings in our studio. The exposures are not long enough for Canon's noise reduction to kick in (according to the documentation this happens with shutter speeds of 1.3 seconds and over). ISO 50 is very clean, and ISO 100 and 200 are perfectly usable. ISO 400 has plenty of visible noise, though it is no worse than the majority of the competition.

ISO 50 100% crop ISO 100 100% crop
ISO 200 100% crop ISO 400 100% crop

Specific Image Quality Issues

Of course all ultra-compact cameras such as this are going to present some kind of compromise when it comes to image quality. The question is how much of a compromise are we prepared to accept in image quality terms to get a camera that is truly pocket-sized?

First the good news; this is a Canon and has all the usual Canon trademarks; excellent, vivid but natural color, very accurate exposure and focus and a surprising amount of detail (see resolution tests). Although the difference isn't huge, you do get slightly better detail (and slightly less noise) than you'd get with the 4MP SD300 (IXUS 40).

Of course it's not all a bed of roses; the SD400 (like the SD300 before it) shows some corner softness at the wide end of the zoom, though it's not strong enough to show in the majority of everyday shots, especially when printed at 'normal' sizes (under 5x7 inches). We found corner softness to be less of a problem than with the SD300 we tested, though this is more likely to be batch variation than a significant difference between the two cameras (which we presume to share the same lens). There is also the usual problem of purple fringing.

Finally, as with pretty much every Canon compact we've tested we found using the clever 9-point AiAF system (which attempts to guess where the subject is in the frame) not only slowed down focusing, but resulted in far more focus errors than the simpler center-focus setting. We would advise turning AiAF off, as we did for this review.

Color fringing

Some purple/blue fringing is present to some degree in all shots containing very bright (especially overexposed) areas, and in some shots it's very pronounced, though it actually seems to be much less of a problem than we saw with the SD300/IXUS 40.

100% crop 35 mm equiv., F2.8

Burnt out highlights/dynamic range

As with all small sensor compacts the SD400 has some problems with high contrast scenes with a very wide dynamic range. It's no worse than its competitors (this is a sensor issue more than anything else), but to Canon's credit the exposure system seems to do an excellent job of retaining highlight detail most of the time, and the default contrast is not as high as on some competitor models, meaning more fine tonal detail is preserved. Be aware, though, that there are times when the difference between the darkest and lightest parts of a scene will mean that something - usually highlight detail - is going to be lost. We also found that there was a slight tendency to underexpose scenes with a lot of sky in the frame, but this is not a serious issue.

100% crop 35 mm equiv., F2.8