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White Balance

The S70 features no less than seven preset white balance settings including the new Flash and Underwater presets (the latter designed to be used in conjunction with the WP-DC40 waterproof case when shooting underwater). The S70 also has manual white balance, accessed via the FUNC menu. Automatic white balance appeared to work well outdoors and in fluorescent lighting but as per previous Canon digital cameras less well in incandescent light where it produced a strong orange color cast.

Outdoor - Auto WB
Red: -0.4%, Blue 0.3%
Excellent

Fluorescent - Auto WB
Red: -2.4%, Blue -1.5%
Good
Incandescent - Auto WB
Red: 8.5%, Blue -12.3%
Poor

Flash Performance

The S70's tiny flash unit has a specified range of 4.2 m at wide angle and 2.0 m at telephoto. In use we found it to meter fairly well (perhaps slightly under exposed, which is better than overexposed!) with good color response and no color cast (good white balance). The flash throttles down well at close distances, so blown-out shots are rare. One complaint is that the auto flash seemed a little too eager to fire - even outdoors in bright light - no doubt due to the automatic backlight detection. It's an idea to turn off the flash in such situations. The other problem is focus - in low light, especially at longer zoom settings - and despite the AF illuminator doing it's business - the S70 often missed focus when shooting indoor portraits with flash.

Skin tone
Excellent color, slight underexposure
Color chart
Excellent color, slight underexposure

Macro Focus

The S70 produced its best macro frame coverage at full wide angle. Inevitably this leads to fairly obvious barrel distortion as well as corner softness. At telephoto coverage is less good (97 mm across the frame) however distortion is nonexistent and corner softness is low. Not bad at all.

Wide macro - 64 x 48 mm coverage
32 px/mm (809 px/in)
Distortion: Low
Corner softness: Average
Equiv. focal length: 28 mm
Tele macro - 97 x 72 mm coverage
21 px/mm (535 px/in)
Distortion: Very low
Corner softness:Average
Equiv. focal length: 100 mm

Barrel and Pincushion Distortion

Considering its size and that it starts at 28 mm equiv. wide-angle the S70's lens performs very well, it does exhibit some distortion at wide angle but in actual fact it's no more than most compacts deliver at 35 mm equiv. The lens exhibits no measurable pincushion distortion at telephoto.

Barrel distortion - 1.4% at Wide angle
Equiv. focal length: 28 mm
Pincushion distortion - 0.0% at Telephoto
Equiv. focal length: 100 mm

Specific image quality issues

First things first; it's hard not to be impressed by the results the PowerShot S70 produces. Not only is the resolution considerably higher than the otherwise equivalent S60, but the new 7MP chip is - as we saw when testing the Sony P150 - noticeably better than its 5MP and 6MP predecessors in its ability to preserve subtle highlight and shadow detail even in scenes with a very wide dynamic range. Noise is very well controlled - though there is evidently some fairly heavy noise reduction going on, meaning the images look a little soft viewed at 100% on-screen. But you can easily sharpen (either by turning up the camera's sharpness setting or, preferably, using Photoshop). And don't forget; viewing 7MP images at 100% on-screen is no indication of print quality (unless you print poster-sized and get nose-close). Color, dynamic range and detail are all excellent, and having a real wide angle increases shooting versatility immeasurably.

Of course there are some problems; purple fringing is an ever-present threat, though again, unless you print above 8x10 inches you won't see it in many shots. There is a slight tendency towards underexposure in the fully automatic modes (which actually benefits highlight detail, and seems to suit this sensor well), so you may need to do a little lightening in Photoshop - but it's still better than overexposure, which would cause burnt out highlights. Finally, we noticed some fall-off in sharpness towards the corners of the image at the 28mm equiv. end of the zoom - see below.

Color fringing

We commented on the problems with purple fringing around highlights in our PowerShot S60 review, and the S70 is no different - it has exactly the same lens system. The fringing is most prominent at the 28mm equiv. end of the zoom, and at F2.8 (the Auto mode tends to use F2.8 too much, presumably to reduce the possibility of camera shake). It is something you need to be aware of when deciding if the S70 is for you, but it doesn't really mar 'normal' prints (10x8 inches and below).

100% crop 28 mm equiv., F2.8

Corner softness

We noticed a rather unusual problem in a handful of shots - all taken at the widest end of the zoom and maximum aperture; blurring (as opposed to lack of sharpness) in one corner. This could be due to various factors, the most likely being a slight misalignment of the CCD or one of the optical elements in the lens. We suspect the latter, especially as the problem was not present in all shots - and because of its asymmetrical nature. Of course this issue may be peculiar to our test camera (though a few users of both the S60 and S70 have reported similar problems). The blurred area is small, and only appears occasionally.

100% crop 28 mm equiv., F2.8
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