Canon Powershot A640 Review
Date: November 27th 2006
Author: Gavin Stoker
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Image Quality
All of the sample images in this Review were taken using
the 10 megapixel Superfine quality mode, which gives an average
image size of around 4Mb - 5Mb.
Noise
There are 5 ISO settings available on the Canon Powershot
A640 which you can select at any time if the camera is in
any of the creative shooting modes. Here are some 100% crops
which show the noise levels for each ISO setting. At the lower
ISO settings there isn't a problem with image noise – though
camera shake can be a problem if shooting handheld in dim
lighting – and even though noise starts to creep in from ISO
400, maximum ISO 800 setting is still very usable.
Sharpening
Here are two 100% crops which have been Saved as Web - Quality
50 in Photoshop. The right-hand image has had some sharpening
applied in Photoshop. The out-of-the camera images are a little
soft at the default setting ideally and benefit from some
further sharpening in a program like Adobe Photoshop. You
can also change the in-camera sharpening level to suit your
tastes via the My Colors menu option.
Chromatic Aberrations
The Canon Powershot A640 dealt exremely well with chromatic
aberrations well during the review, with only very limited
purple fringing present around the edges of objects in certain
high-contrast situations, and only in a handful of test images.
Macro
The Canon Powershot A640 offers a Macro setting that allows
you to focus on a subject that is just 1cm away from the camera
when the lens is set to wide-angle. The first image shows
how close you can get to the subject (in this case a compact
flash card). The second image is a 100% crop.
Flash
The flash settings on the Canon Powershot A640 are Auto,
Manual Flash On / Off, Slow Sync Speed and Red-eye Reduction.
These shots of a white coloured wall were taken at a distance
of 1.5m.
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Auto Flash - Telephoto (140mm) |
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And here are some self-portrait shots. If you opt to use
flash for portraits, it's difficult to avoid the effects of
red eye (despite the camera's anti red-eye flash setting).
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Flash On (100% Crop) |
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Flash - Red-Eye Reduction (100%
Crop) |
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Night Shot
The Canon Powershot A640 maximum shutter speed is 15 seconds,
which is great for night photography. The shot below was taken
using a shutter speed of 1/5 second, f/2.8 at ISO 400. I've
included a 100% crop of the image to show what the quality
is like. The camera takes the same amount of time again to
apply noise reduction, so for example at the 8 second setting
the actual exposure takes 16 seconds.
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Night Shot (100% crop) |
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Overall Image Quality
Perhaps inevitably there is occasional visible camera shake
and image softness when shooting at maximum telephoto setting
– even in daylight. Under strong winter sun there's also the
danger of lens flare and loss of detail in the highlights,
though this is no better nor worse than competing brands.
Pixel fringing, though noticeable on close inspection between
areas of high contrast, isn't problematic, and overall images
are sharp and clear with, for the most part, a pin sharp level
of detail, even if to the naked eye they don't seem significantly
better than those from a seven or eight megapixel compact.
Perhaps the resolution of the LCD screen could be boosted
(from 115k pixels), as it's tricky to determine whether a
subject is sharply in focus when reviewing on the LCD alone.
Still, colours are pleasingly naturalistic if slightly warm,
with skin tones particularly flattering. And though greens
and reds are already pretty vivid, there's of course also
the opportunity to boost saturation in camera if needed. At
the lower ISO settings there isn't a problem with image noise
– though camera shake can be a problem if shooting handheld
in dim lighting – and even though noise starts to creep in
from ISO 400, maximum ISO 800 setting is still very usable.
If, however, you do opt to use flash for portraits instead,
it's difficult to avoid the effects of red eye (despite the
camera's anti-red eye flash setting). To sum up, a performance
that, while it may not be 100% successful, delivers the goods
more often than not, making the Canon Powershot A640 a reliable
and slightly more flexible choice of snapshot camera.
 PhotographyBLOG
is a member of the DIWA
organisation. Our test results for the Canon Powershot A640
have been submitted to DIWA
for comparison with test results for different samples of
the same camera model supplied by other DIWA
member sites.
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