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Photographic tests

White balance

The SD850 IS 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 outdoor sample shots). Indoors the situation is slightly different. As we've seen with most Canon PowerShots incandescent (tungsten) lighting causes a fairly strong orange color cast (though manually choosing the right preset gives a perfectly neutral result). We've spoken to Canon about its 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'. Uncharacteristically for a Powershot the Auto WB performance under fluorescent light is poor as well with a strong yellowish-greenish cast on images. Again, using the WB preset will sort this out and for perfectionists there is always the Custom White Balance option.

Auto White Balance Flu Preset Auto White Balance Incandescent preset
Fluorescent light - Auto white balance poor,
Preset white balance good
Incandescent light - Auto white balance poor,
Preset white balance excellent

Flash

The SD850's built-in flash has a quoted working range of 0.5m - 3.5m (1.6 - 11 ft) at the wide end of the zoom and 0.5m - 2.0m (1.6 - 6.6 ft) at the tele end. This is not exactly impressive and you'll run out of flash power pretty easily, even when using Auto ISO, if you try to shoot anything too far away.

In our real-world tests the flash did a decent job with a very slight warm tone (which is nice). The flash is also very fast - even with the red-eye reduction turned on, meaning you won't miss any spur of the moment shots waiting for the flash. 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 2.0m.

Red-eye reduction does a decent job although it has to be said it is not 100% reliable, you still get the occasional zombie stare in your flash portraits.

Skin tone -
Excellent color, good exposure.
Flash chart - Good exposure, good color.

Macro

As is common to most compact digital cameras the SD850's macro mode is most effective at the wide end of the zoom, where you can get as close as 2cm - not bad at all for an 'ultra-compact', capturing an area just over 3cm across. At the long end of the zoom the performance is less impressive - 40cm subject distance capturing an area just over 10cm wide - but still pretty useful. As you would expect there is some visible distortion when when shooting very close up at the wide end, but it is not too strong, and certainly less so than many of its competitors.

Movie mode

As is now the norm on cameras of this type the SD850 offers a maximum movie size of 640x480 pixels - enough to fill most television screens at 30 frames per second. It also offers options to shoot at smaller sizes and lower frame rates. There are also a 'high frame rate' option that shoots 320x240-pixel movies at 60fps and a time lapse option. The latter records an image per second or per every two seconds and then plays the movie at the normal speed of 30fps.

Overall quality is excellent, with movies very smooth and showing few compression artifacts. The AVI files are large - at the best quality setting (640x480 / 30fps) you're burning around 2MB every second, so if you intend to shoot a lot of movies you're going to need to invest in some big, fast SD cards.

In standard movie mode you can use digital zoom during filming. In the other modes you cannot zoom at all.

Sample movie: 640 x 480 pixels @ 30 fps
File size: 11.9 MB, 6 secs

Click on the thumbnail to view the movie (caution: large file!)

Resolution

The SD850 has two million pixels more than its predecessor, so it shouldn't come as a surprise that our measured resolution has increased as well. Resolution is good for this class of camera but the results are not the cleanest we have ever seen. There is visible moiré and also quite some jaggedness on the diagonal lines. To be honest though, these minor flaws are much more likely to show on our test charts and not on a normal sized real-life image (because that is what test charts are designed for).

Crops

Click here for the full resolution test chart

Horizontal LPH

Absolute resolution 1600 LPH
Extinction resolution 2100 LPH *

*moiré visible

Vertical LPH

Absolute resolution 1600 LPH
Extinction resolution 2200 LPH *

*moiré visible

Distortion and other image quality issues

The SD850 shows moderate distortion at the wide end of the zoom - 1.2% barrel distortion (click here for test chart), for a camera of this type this is well within acceptable limits and nothing to worry about. There is no measurable distortion at all at telephoto end (click here for test chart).

General comments

The SD850 generally produces appealing 'ready for print' images. Depending on your preferences in terms of sharpness you could consider adding unsharp mask a tad. Out-of-cam results are comparatively soft viewed at a pixel level, but we this i better than an over sharpened image. The colors and contrast are on the vivid side but not unnatural. There is no reason for major concern when analyzing the SD850's output, the only issues which are really worth mentioning are the highlight/channel clipping and purple fringing described in the following paragraphs. On very fine detail you'll sometimes also find textures to appear slightly blurry or smeary, even at low ISO. This is fairly common to most small-sensor compact cameras and mainly caused by noise reduction being applied even at base ISO.

Highlight clipping / dynamic range issues

The SD850 has a fairly pronounced tendency to clip highlights. Again, this is, to a certain degree, common to almost all small-sensor digital compact cameras, mainly caused by a limited dynamic range of the sensor and a steep tone curve applied to the image. This phenomenon often manifests itself in completely washed out skies on overcast days. In our sample image (definitely the worst example out of our 400+ shots) the sky merges with the facade of the building into one large unidentifiable white mass; not very nice at all. The situation is not exactly helped by the completely inappropriate exposure chosen by the camera for this particular scene. You can mitigate this issue by carefully applying some negative exposure compensation in critical shooting situations and/or reducing contrast in the MyColors menu.

In the same image you can also easily spot some quite severe purple fringing on the branches of the tree. The SD850 produces some purple fringing in typical (high contrast) situations but luckily it is rarely as bad as seen here. Exposure compensation will, to a certain degree, also reduce the impact of this problem. Whatever is left needs to be removed in post processing although in most cases this won't be necessary as the fringing is not serious enough to show in normal sized prints.

Red channel clipping

Reds generally appear slightly more vivid on the the SD850 than other colors. In extreme situations this can lead to a clipping of the red channel, resulting in a purple/pinkish color on subjects which in reality are bright red. Unfortunately there is little more that you can do about this than to watch out for the problem to occur. If it happens you might want to try and reduce saturation in the MyColors menus. You can later pull up the green and blue channels again in your imaging software. Just to be clear, this is not a frequent occurrence. We found about 2 examples amongst our 400+ gallery shots.

35mm equiv., F2.8 35mm equiv., F2.8
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