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White Balance

The G7 features a grand total of seven white balance settings including the default automatic mode. There's also a manual (custom) white balance option, which is created by aiming the camera at a white (or gray) subject and pressing the SET button. Automatic white balance appeared to work well outdoors and not terribly in fluorescent lighting, but as per previous Canon digital cameras less well in incandescent light, where it produced a pronounced orange color cast. It is advisable to switch to the tungsten preset (or set a custom WB) when shooting indoors if you don't like a warm cast to your indoor shots.

Incandescent - Auto WB
Red 11.6%, Blue -17.0%
Poor
Incandescent - Incandescent preset WB
Red -1.7%, Blue -1.9%
Good
Fluorescent - Auto WB
Red 3.8%, Blue -17.9%
Poor
Fluorescent - Fluorescent preset WB
Red 1.4%, Blue -5.1%
Average

Flash Performance

The built-in flash unit has a specified range of 4.0 m at wide angle and 2.5 m at telephoto (when the ISO is set to auto) - which is fine for social snaps and the occasional bit of fill-in, but is hampered by the relatively small maximum aperture as you move up the zoom range. In use we found the flash to work very well indeed, with most indoor flash shots perfectly exposed. The FUNC menu offers a Flash Exposure Compensation setting (-2.0 to +2.0), and the AF illuminator helps focus in low light. We found the red-eye reduction to work well at shorter distances but to be less effective if you move further away and zoom in. One thing worth noting is that the shutter lag when using flash (because of the pre-flash metering) increases to around half a second. On a more positive note you can use the flash in continuous (burst) mode.

Of course the inclusion of a dedicated hot shoe means you can expand the G7's flash capabilities as and when you need to.

Skin tone - Slight warm tone, excellent exposure Color chart -Slight warm tone, excellent exposure

Macro Focus

Macro performance has been boosted over the G6, with the minimum focus distance at the wide (35mm equiv.) end of the zoom reduced to a very impressive 1cm, allowing you to capture an area around an inch across. Of course it's not always practical or desirable to get that close, which is why macro performance at the long end of the zoom is also important. At the 210mm equiv. end of the zoom the G7 can focus down to 50cm, capturing an area just over 10cm across. There is some corner softness at the long end, but distortion is very low.

Wide macro - 24 x 18 mm coverage
147 px/mm (3731 px/in)
Distortion: Average
Corner softness: Average
Equiv. focal length: 35 mm
Telephoto macro - 102 x 76 mm coverage
36 px/mm (903 px/in)
Distortion: Low
Corner softness: Above average
Equiv. focal length: 210 mm

Barrel and Pincushion Distortion

The G7 exhibits pretty low distortion given the large focal length range - 1.2% barrel distortion at the wide end, and only the barest measurable distortion (0.2%) at the full 210mm telephoto end. There is also virtually no vignetting at either end of the zoom. There is a hint of corner softness and chromatic aberration when shooting at either end of the zoom with the aperture wide open.

Barrel distortion - 1.2% at Wide angle
Equiv. focal length: 35 mm
Pincushion distortion - 0.2% at Telephoto
Equiv. focal length: 210 mm

Specific image quality issues

Overall I was very impressed with the G7's output - and given its position at the top of the PowerShot range I would have been surprised if it hadn't been up there with the best. Of course you'll get the best results at ISO 80 and 100 - once you hit ISO 200 the effects of noise and noise reduction start to take their toll on fine detail, and at ISO 800 and above quality is seriously compromised. Nothing unusual there.

Although the output is a little soft (you get the feeling this sensor needs a lot of 'work' doing on it to produce clean results), edge-to-edge performance is good across the zoom range once you close down the aperture a stop or two, focus very reliable and color superb; just punchy enough to produce attractive results 'out of the box' without looking unnatural or over-processed. Of course the extensive in-camera parameters for color, contrast, saturation and sharpening allow you to fine-tune the output to your own tastes and needs - especially important given the lack of raw file support.

On the downside the metering is easily fooled by very bright and/or contrasty scenes, and I found myself with a -0.3 or -0.6 EV compensation almost permanently dialed in to avoid the consistent overexposure and highlight clipping that shooting at the wide end of the zoom outdoors tended to produce. This isn't helped by the fairly steep default tone cure and limited dynamic range - this is one of those cameras that - at its default settings - is very sensitive to exposure errors, and one that benefits greatly from a little manual intervention. Turning down the contrast helps a little, as does using the histogram to expose slightly 'to the left'.

Ironically I found the G7 to be one of the worst cameras I've ever used for camera shake; down I suspect to the long zoom and image stabilization encouraging me to take shots at way too low shutter speeds, compounded by the physical design of the camera, which isn't that easy to hold steady.

Purple fringing & Chromatic Aberrations

Although nowhere near as bad as we've seen on some Canon compacts, the G7 does suffer from some purple fringing, particularly at the wide end of the zoom and in contre-jour situations such as this. There is also some chromatic aberration visible at the wide end of the zoom and wide apertures (this shows as red/blue fringing on either side of high contrast edges).

100% crop 35mm equiv., F2.8

Exposure / Dynamic range / clipping

By far my biggest problem with the G7 - and the cause of the majority of failed shots - is the clipping of highlights when shooting in less than perfect conditions (particularly on bright, hazy days). The clipping is caused by a combination of limited dynamic range, the camera's default tone curve and a tendency to overexposure in such circumstances. With practice it's possible to reduce the likelihood of highlight clipping by careful exposure and use of a lower contrast setting when shooting at the wide end of the zoom on bright days, but this does hinder the G7's ability to be used as a 'walkaround' camera for quick snaps.

100% crop 35mm equiv., F4.0
100% crop 46mm equiv., F4.0
100% crop 35mm equiv., F2.8, -1.7EV exposure comp.
100% crop 35mm equiv., F4.0

 

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