Canon PowerShot G2 Review
Overall Image Quality
Overall the G2 puts in a very commendable performance. Metering is improved thanks to the new evaluative metering mode, in a session of shooting I didn't once have to reach for the exposure compensation control. Canon have updated the camera's colour processing algorithms to include the stronger colour and more accurate white balance we've seen since the IXUS 300 and A20. And resolution is also there, the lens seems to be more than capable of squeezing a full four megapixels of resolution out of the sensor.
This camera really loves colour, and especially blue skies which it seems to draw out almost as though it has a permanent polarizing filter, rich and deep blue skies seemed to be signature of images taken with the G2.
Something else the G2's algorithms manage to do is maintain dynamic range, they seem to deliberately push dark areas up the grayscale very slightly (to maintain shadow detail) and will do what they can to maintain the top end without creating a very sharp cut-off at the point of overexposure. The deliberate ramping of the black point is something we first saw on the IXUS 300 and it really does help to maintain shadow detail.
Gone are some of the complaints of last year, but there are now hints of sharpening / Bayer interpolation artifacts in the way of jagged diagonals, something some people have noted on EOS-D30 JPEG files.
Purple Fringing (Chromatic Aberrations)
The G2 suffers a lot less in the way of chromatic aberrations. In every day shots there's some visible blooming (the overflow of charge from over exposed pixels to areas of contrast) but there's really nothing in the way of the strong purple (or magenta) fringes we saw when we tested the G1. There is some CA but it became apparent that it was far reduced in 'every day shots'.
|Very little visible chromatic aberrations in an "every day shot"|
|Our now standard chromatic aberration test shot|
Our standard test shot did show up a very slight fringe and blooming.
Barrel and Pincushion Distortion
As we'd expect (this is the same design and focal length lens as last year) the G2's lens distortion measured exactly the same as the G1. There was mild barrel distortion at full wide angle and very slight (hardly noticeable) pincushion distortion at full tele photo.
|Barrel Distortion, 1.1% @ Wide Angle||Pincushion Distortion, 0.5% @ Full Tele|
Jagged (stepped) diagonals
This is an odd artifact which I've only ever seen reported on EOS-D30 JPEG's. It occurs on diagonal lines which are not quite at 45 degrees, these lines are then 'made up' of groups of pixels in a 45 degree line, stepped one pixel and then repeated. This can be attributed to either a problem with the Bayer interpolation algorithm or sharpening algorithm. They exists also in RAW images converted using the supplied acquire module or RAW file converter. You can clearly see this pattern in the examples below (magnified 200%).
It's unlikely these artifacts would be visible on a printed page or computer monitor (and normal viewing sizes) but they are there, and noted.
Having gone back through over a thousand sample images shot with the G2 I'm happy to say that although these artifacts exist in some shots they're certainly not common to all and can be reduced by shooting with sharpening set to -1. HOWEVER, then images will need an unsharpen mask if they're to be used at their native resolution.
The effect can be seen in the 'uneven' width of the vertical lines on our resolution test chart, in the samples below you can see a comparison of Normal Sharpening, Low Sharpening and a RAW file acquired as linear (16-bit, no processing) which has been level adjusted and had a 150% unsharp mask applied (resaved as JPEG from Photoshop).
|JPEG Normal Sharpening||JPEG Low Sharpening||RAW Linear|
CONCLUSION: It does to me at least seem to be an effect of (error in?) Canon's bayer pattern interpolation algorithm which is then being enhanced by sharpening. Using lower sharpening will help some. The RAW linear did look the best overall but is impractical for large numbers of images and it is difficult to return a linear acquired image to its true tone / colour balance.
COMMENT: Despite some comments made on our discussion forums this newly added review item is NOT a retraction, if anything it is designed to highlight this problem and indicate that it does need solving.
As mentioned earlier on this page the G2's white balance presets (Sunny, Cloudy, Incandescent etc.) have all been tweaked and tuned and performed much better than the G1 (no hue shift, good 'white is white'). Auto white balance didn't fair so well, being only really usable in natural light. Manual white balance seemed to work well under any type of light. Note also that Canon has added a new 'Fluorescent H' mode for different colour tubes.
|Outdoors, Auto||Outdoors, Sunny||Outdoors, Cloudy||Outdoors, Manual|
|Incandescent, Auto||Incandescent, Incan.||Incandescent, Manual|
|Fluorescent, Auto||Fluorescent, Fluor.||Fluorescent, Fluor. H||Fluorescent, Manual|
Dynamic range simply defines the range of light the camera is able to capture before it either loses detail in darkness (shadows for example) or blows out a highlight (edges of chromed metals are good examples of this). Most consumer digital cameras only have a 8-bit analog to digital converters, plus their CCD's are not built to have a particularly large dynamic range.
Using our new dynamic
range measurement method we measured the G2's dynamic range as (higher
numbers are better except for noise):
* In-camera sharpening set to "-1"
Noise is low and dynamic range is high at the lower ISO's, the G2's clean ISO 50 produces impressive dynamic range results, ISO 100 is also fairly good (though not as good as some), range drops off fairly significantly at higher sensitivities.