Canon SD900 Digital ELPH (IXUS 900 Ti) Concise Review
The SD900 has five white balance presets (daylight, cloudy, tungsten, fluorescent and 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 incandescent (tungsten) lighting causes a fairly strong orange color cast (though switching to manual gives a pretty neutral result). If you don't like the warm tone, you need to switch to custom WB.
|Auto White Balance||Fluo Preset||Auto White Balance||Incandescent preset|
|Fluorescent light - Auto white balance average,
Preset white balance good
|Incandescent light - Auto white balance average, Preset white balance average|
As is common to most compact digital cameras the SD900's macro mode is most effective at the wide end of the zoom, where you can get as close as 5cm - not bad for an 'ultra-compact', capturing an area 52mm across. There are cameras with better macro performance (even in the SD/ELPH range), but the SD900's capabilities are fine for the typical user of a compact 'point and shoot' model. At the long end of the zoom the performance is less impressive - 30cm subject distance capturing an area just over 10cm wide - 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.
Resolution is excellent - and a big leap over the 7MP ELPH/IXUS models - a reflection of the additional megapixels and the better lens. There's a hint of moiré at the very highest frequencies, but nothing worth worrying about. The resolution chart is also pretty clean, without excessive sharpening or visible artefacts, and corner sharpness isn't bad at all.
|Click here for the full resolution test chart||
resolution 1700 LPH
resolution 1625 LPH
Distortion and other image quality issues
At the wide end of the zoom distortion is reasonably low - 0.9% barrel (click here for test chart) is nothing to worry about on a camera of this type. There is only the slightest (0.1%) measurable distortion at all at telephoto end (click here for test chart).
Overall impressions are - taking into account the obvious compromises demanded of any slim 'style' compact user - very positive indeed. Exposure and focus are very reliable indeed - something you should be able to take for granted in a 'point and shoot' model like this but you so rarely can. Even up close, at a pixel level, the SD900 doesn't disappoint - the images are clean and detailed (as mentioned elsewhere they aren't significantly different to the PowerShot G7).
Of course there are some minor problems - the default contrast is a little high for my liking (though it can be reduced) and there is the usual problem of highlight clipping in very bright conditions (although as mentioned elsewhere this sensor seems quite good at hanging onto highlights and the exposure system does a good job in most circumstances). There is a small amount of corner softness (visible in the fringing example below) at the wide end of the zoom wide open, but it's nowhere near what we've seen in previous ELPHs - and simply isn't an issue in 99% of 'real world' shots.
Although you have to look for it, you can find some purple fringing around overexposed areas such as this. It's not a major problem (unless you shoot a lot of contre-jour foliage like this), and is certainly less so than it was with many earlier SD cameras.
|100% crop||37mm equiv., F2.8|
With tiny, high pixel count chips noise is always going to be an issue, and to a large degree this is more a test of the effectiveness (both measurable and visible) of a camera's noise reduction system. Designers have to balance the desire to produce smooth, clean results with the need to retain as much detail as possible (if you blur away the noise, you blur away image detail too). The SD900 features the same (as far as we know) 1/1.8-inch 10MP sensor as the PowerShots A640 and G7, and it also sports Canon's new DIGIC III processor.
When we tested the SD800 IS recently we had mixed feelings about the DIGIC III's noise reduction, which we found to produce slightly more obvious artefacts than previous generations. The SD900 isn't a whole lot better, but it is a little better at ISO 100-400 (at ISO 800 and especially ISO 1600 the output is firmly in the 'emergency use only' camp). This would appear to be down to the difference between the 1/1.8" 10MP used here and the 1/2.5" 7MP used in the SD800 IS.
Noise at ISO 80-200 is low, though (as with all today's compacts) you'll only preserve the finest low-contrast detail if you shoot at the lowest setting. As mentioned earlier (and as is obvious from the crops and graphs below) noise - and visibility of noise reduction effects - rises rapidly over ISO 400.
|ISO 80||ISO 100||ISO 200||ISO 400||ISO 800||ISO 1600|
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity is on the vertical axis.
Low contrast detail
What the crops and graph don't show is the effect of noise reduction on low contrast fine detail such as hair, fur or foliage. An inevitable side effect of noise removal is that this kind of detail is also blurred or smeared, resulting in a loss of 'texture'. In this test the crops below show the effect of the noise reduction on such texture (fur) as you move up the ISO range.
|ISO 80||ISO 100||ISO 200|
|ISO 400||ISO 800||ISO 1600|
As the crops above show, at ISO 80-200 the loss of fine detail is restricted to the very finest low contrast areas, and even ISO 400 maintains enough detail for most purposes. ISO 800 and 1600 maintain a little - but not a lot - of the luminance detail, but the results look noisy and by the time you get to ISO 1600 are to all intents and purposes useless for anything other than emergencies. Still, compared to the smearing of low contrast detail we see with some competitor cameras it's obvious Canon is working hard to retain detail at low to middle ISO settings. We did find that - like all modern cameras - if you shoot landscapes at anything over ISO 80 there is some loss of the detail in distant foliage.