Canon PowerShot S40 Review
The S40's all new super-slim flash unit has a rated range (at Auto ISO; 50-100) of 0.35 - 4.8 m (at wide angle) and 0.35 - 3.0 m (at telephoto). These are pretty ambitious figures for such a small flash, and as you can see from our test results below the S40's flash turned out to be less powerful than we would have liked.
Overall clean exposures and the additional long exposure noise reduction (which automatically kicks in for exposures longer than 1.3 seconds) means that the S40 is more than capable of taking very nice night exposures right the way up to its longest exposure of 15 seconds.
|ISO 50, 10 sec, F2.8|
|ISO 50, 15 sec, F3.5|
Barrel and Pincushion Distortion
As with most digital camera lenses the S40's lens exhibits just under 1.0% barrel distortion at wide angle (35 mm) but Kudos for no measurable pincushion distortion at full telephoto (105 mm).
|Barrel Distortion, 0.9% @ wide angle||Pincushion Distortion, 0% @ telephoto|
Purple Fringing (Chromatic Aberrations)
Despite a long hunt through the several hundred samples we shot with the S40 I couldn't find a definitive or strong example of chromatic aberrations in 'every day' shots. Our standard test shot did managed to drag some evidence of the purple fringe, but far less than we've seen on other digital cameras. There is some evidence of blooming between highly overexposed and dark areas of the image.
|Hard pressed to find evidence of chromatic aberrations in "every day" shots|
|Our now standard chromatic aberration test shot|
Overall Image Quality / Specific Issues
Overall the S40 has excellent image quality. Colour balance is good, colours are strong but not oversaturated and the inclusion of colour saturation control means you can always tweak colour output to your preference. Tonal balance and metering are also good, in comparison (and as we'd expect) in this respect the S40 performs virtually identically to the G2.
Clearly where the S40 isn't as strong as the G2 is the speed (maximum aperture) and sharpness of its lens, there is a hint of soft corners at wide open apertures (F2.8 at wide angle, F4.9 at telephoto) and although resolution is very good (well above any three megapixel) it is slightly less than the G2. All that said the S40 does exactly what it promises, it provides good balance, good colour and a respectable four megapixel resolution in a compact form factor.
Just like a few other 4+ megapixel digital cameras I've reviewed the S40 I had did have a "dead pixel", this is a pixel which will always register an incorrect (typically the same) value (even at relatively 'normal' exposures). This particular camera had a dead pixel at location 764, 487, because of the bayer interpolation algorithm it also creates a dark halo around itself (and thus affects at least seven other pixels).
Is this a reason to return your camera? The jury is still out.. The dead pixel on this particular cameras was not visible in 95% of our test shots. And certainly it appears that 4+ megapixel CCD's are more prone to dead pixels, and indeed some manufacturers have built systems into their cameras which map these pixels out (so that they're simply not seen).
As we'd expect the S40 also exhibited the same diagonal jaggies (lines which are near to 45 degrees made up of joined 45 degree lines) which we saw on the G2 (and to some degree the EOS-D30). This appears to be a side effect of the cameras sharpening algorithm (as turning sharpening down virtually removes it). We only observed this effect in a low percentage of the 'every day' sample shots we took and then only at 200% magnification.
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