Previous page Next page

Noise

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). Although it's nowhere near as damaging as some other manufacturers' noise reduction, the SD800 is the first Canon we've seen with obvious noise reduction artefacts at higher ISO settings, giving the results (if viewed at 100%) a slight 'watercolor' feel, with the loss of fine, low contrast detail.

ISO 80 ISO 100 ISO 200 ISO 400 ISO 800 ISO 1600
100% Crops

Noise graph

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity is on the vertical axis.

Overall noise levels are lower than the SD700 IS - this would certainly appear to be the result of noise reduction, not the sensor itself. At ISO 80-200 noise - and noise reduction are fairly low. They're also a lot lower than the A710 IS (which we presume uses the same sensor) - and you can easily see that the noise reduction is a lot higher (by comparison the A710IS looks very noisy). This is the first time we've tested a Canon compact with the new 1/2.5 7MP sensor and DIGIC III processor, and it seems the new hardware represents a slight change in policy for Canon, with the emphasis on low noise, producing smooth results at the expense of fine detail. It won't bother the typical user producing 6x4-inch prints, but it does bother us.

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.

100% Crops
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 (bottom right of these crops), 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.

Let's take a quick look at a more difficult challenge (I would recommend downloading the full size images to take a better look if you're interested) - very fine, very low contrast detail, in this case distant foliage:

100% Crops
ISO 80 ISO 100
ISO 200 ISO 400

If you look at the area on the left of these crops you can see the hanging vines in the ISO 80 shot, they're beginning to disappear in the ISO 100 example, and have been blurred away completely by ISO 200. Although by no means unique to the SD800 - as manufacturers continue to push sensors and strive for 'smooth' output it is increasingly the norm - it does mean that 'serious' users will need to stick to ISO 80 if they want to preserve the fine detail in their landscape shots. If you never look that closely (or produce standard sized prints) you can get away with ISO 200 or 400, but be warned that the results will have a little bit of 'watercolor' about them. Thank goodness for image stabilization...

Optical image stabilization

Like the SD700 IS, the SD800 IS sports Canon's optical image stabilization system, though with a 105mm (equiv.) maximum focal length camera shake is only likely to be an issue in when the light starts to fail - at the 28mm wide end of the zoom I was getting acceptably sharp hand-held results at 1/15th sec without IS more often than not. It is, however, undeniably useful for tele or macro shots in anything other than perfect light, and I saw virtually no camera shake in the 600 or so shots taken for the gallery.

There are three modes: Continuous (IS on all the time), 'Shoot only' (IS is activated at the moment the exposure is made) and Panning (for horizontally panned shots).

The first option makes framing easier - the IS system steadies the preview image - but the second is easier on the batteries and, in theory more effective (though as usual our test showed this to be by no means guaranteed - at very long exposure settings the continuous mode seems to work better).

Although we've no definitive test for IS systems in real-world use, the SD800's stabilization works pretty well 99% of the time, though as ever the effectiveness will vary from user to user depending on their particular type of shake. It's not the best IS system we've ever tested (or even the best Canon IS system), but our tests would indicate that if you're getting a good 2 stops advantage in most cases (1/25th sec exposures at the long end of the zoom were nearly all blur-free), though once you get to three or four stops the hit rate falls dramatically. It also makes for much less jerky movies.

As with all IS systems it's not infallible, nor is it easy to predict which setting will be more effective (I tended to leave it on 'continuous' when shooting tele, as the stabilized preview image makes framing so much easier), but if you don't expect miracles and take a few 'safety shots' in borderline cases it's rare you don't get at least one 'keeper'.

1/10 second, hand-held, 105mm (equiv.)
IS off IS on ('continuous' mode) IS on ('shoot only' mode)
1/6 second, hand-held, 28mm (equiv.), Macro mode
IS off IS on ('continuous' mode) IS on ('shoot only' mode)
Previous page Next page

Comments