The Canon SD20 is an extremely compact and thin 5 megapixel
camera. But the trade-off for that diminutive size is that
it has a single focal length lens and no optical viewfinder.
Instead of an optical zoom the SD20 offers a 6.5X digital zoom, but it
would be unwise to see the digital zoom as an acceptable replacement
for an optical zoom. As the digital zoom's magnification is increased,
it simply crops a progressively smaller area at the centre of the frame
producing an image that shows a field of view comparable to a longer
focal length.
That small cropped
section of the full 5 megapixel image is then increased back
up to a 5 megapixel size — or to any other image size currently
selected — through an interpolation process that fills
in the missing pixels by creating new ones based on those that
are nearby. The result is a considerably coarser image. A digitally
zoomed image can never be as sharp as an image captured with
an optical zoom.
Still, if the use of the digital
zoom is limited to a maximum of 2X, the digitally zoomed photo
can be printed out to a postcard size without any serious loss
of sharpness thanks to the high resolution CCD used in the SD20.
Moreover, the 6.4mm lens of the SD20 — comparable to a
39mm lens on a 35mm film camera — yields excellent images
that show a high level of detail and only a slight amount of
barrel distortion.
On the exposure side, we noted
a tendency for the evaluative metering pattern to give preference
to the exposure of shadowed areas over directly lit ones. In
a number of photos, this tendency resulted in somewhat over-exposed
highlights, and the overexposure revealed some purple fringing.
This said, if the oldest rule of photography is applied — keeping
the sun at one's back — the SD20's evaluative metering
yields perfectly exposed photos.
While the lack of a zoom lens is
more of an inconvenience, since one can usually move closer to
a subject, the lack of an optical viewfinder can be more of a
problem. For one, although the SD20 offers a very reasonable
operating time on a fully charged battery, the constant use of
the LCD monitor is a drain on the battery. For another, the LCD
monitor easily becomes hard to see under bright light, and as
there is no viewfinder to fall back on, framing a subject properly
or ensuring that the horizon is level, can be difficult.
Likewise, an indication of shutter
speed and aperture would have been useful. Rather than indicate
the shutter speed, the SD20 displays a small camera-shake icon
on the screen when the camera is using a slow shutter speed.
Part of the beauty of digital photography is the user's ability
to see the impact of camera settings on the quality of the image.
And, when this most basic information — the shutter speed
and aperture — is absent and replaced by an arbitrarily
displayed icon, an opportunity to learn is lost.
With its 5 megapixel CCD, the SD20 easily yields photos that
can be printed out to an 8 x 10 size (20 x 25 cm); a remarkable
feat from such a small camera. Indeed, the appeal of the Powershot
SD20 lies in its high resolution image, compact size, solid
construction and stylish design. Yet, the lack of an optical
zoom, or for that matter of an optical viewfinder, may deter
potential purchasers.
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