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1280x960 resolution |
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Compact, rugged case |
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2.5x Optical Zoom Lens |
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Great low-light ability (up
to ISO400) |
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Panorama support, including
2x2 matrix! |
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Canon PowerShot A50 Review Index:
Exposure
The PowerShot A50 exposure system covers an unusually
broad range of illumination for a digicam in its price range,
although we're a little puzzled by Canon's specifications in
this area. Canon claims a "metering" range for the
camera of EV2 to EV16.5. This is both a narrower range and one
skewed toward lower values than our own calculations would indicate.
Although Canon doesn't specify an aperture range for the A50
(and indeed no aperture value is recorded in its JPEG file headers),
even the maximum aperture of F/4.0 at the telephoto end of the
lens' range, combined with the ISO 100 light sensitivity and
minimum exposure time of 1/750 second translates to an EV value
of roughly 18.5. At the low end of the range, an exposure time
of 2 seconds at ISO 400 (in low resolution mode) and the f/2.6
maximum wide-angle aperture translates to an exposure level of
about EV5. (In our own tests, the A50 appeared to work well down
to a minimum exposure level of about EV 7, with usable results
as far down as EV5. ("Usable" here means that we could
extract fairly good-looking, albeit somewhat noisy images from
the camera's pictures, using Photoshop or some other image editing
program to adjust the brightness and contrast.) While we don't
have a formal test for measuring maximum EV levels, some playing
around with a bare 60-watt light bulb seemed to indicate that
the A50 works fine up to at least EV21.5.
As noted earlier, the camera normally operates at an ISO value
of 100. In low-resolution mode, it can combine groups of 4 adjacent
CCD pixels into a single, virtual, "super pixel," with
four times the light sensitivity. This results in an ISO rating
of 400 for this operating mode. Interestingly though, it appears
that the camera's manual exposure-adjustment feature works by
boosting or cutting the amplification in the camera's electronics.
Thus, when you increase or decrease the exposure with the manual
exposure compensation adjustment, the shutter speed (and presumably
the lens aperture) remain the same, despite the evident increase
or decrease in the brightness of the captured image. Thus, it
seems the A50 can actually behave as though it has an ISO sensitivity
of 400, even in high-resolution mode, albeit at some cost in
increased image noise. Another oddity is that the ISO 400 of
the low-resolution mode doesn't seem to translate into a lower
absolute light capability, but rather to shorter exposure times
at the same minimum light level. We found that the maximum exposure
time for low-resolution (ISO 400) shots appeared to be one second,
and the low-resolution mode didn't appear to extend the ultimate
minimum light level any lower than that of the high-resolution
mode. On the other hand, at higher light levels, the exposure
times were definitely shorter, making hand-held shots more practical.
We've mentioned the A50's manual exposure-compensation adjustment
several times now, and this is one area where we initially had
a minor quibble with the unit's creators, in the realm of user-interface
design: We find ourselves using exposure compensation fairly
frequently with digicams, and so like to have the controls for
it quickly accessible. On the A50, this function appeared to
be consigned to the LCD menu system, requiring several button-presses
to access it. We were thus very pleased when we read the manual
and discovered that you can access the exposure compensation
immediately, just by pressing the "Set" and "-"
buttons simultaneously. This is a great shortcut, and very practical
in actual use. (The A50 has several shortcuts like this: We highly
recommend you take the time to read the manual!) However you
choose to activate the exposure-compensation function, the display
is very functional, showing both a "live" view of your
subject with the current compensation applied to it, and a scale
from -2 to +2 in 1/3-unit increments showing the currently-selected
compensation level. The process of making these adjustments is
a little slow though, as the camera pauses for a second or so
after each incremental adjustment, before allowing you to move
the control further.
Continuous (Burst) Mode
To capture fast-changing action, the A50 provides a "continuous"
shooting mode, in which the image size is automatically set to
small, and the camera continuously captures images at roughly
1.2 frames per second until it runs out of buffer memory - 10
frames or so for the higher-quality compression setting, 15 frames
for the lower-quality one.
White Balance
Like most digicams these days, the PowerShot A50 provides several
preset white balance options, in addition to the default automatic
mode. Available settings include Auto, Daylight, Cloudy, Fluorescent,
and Tungsten. White balance settings tend a bit more toward art
than science with digicams, in that you often want the camera
to NOT remove all the color cast of the original lighting, to
preserve more of the "feeling" of the scene. Thus,
there's a range of acceptable behavior for camera white-balance
controls, ranging from more to less aggressive in their removal
of color casts. Overall, the white balance of the A50 tends more
toward the less-aggressive end of the scale, leaving more of
the scene coloration in the final image than we'd prefer in most
cases. We liked its handling of scenes with relatively little
color cast, but would have preferred a more neutrally-colored
final result in our indoor portrait shot. To its credit though,
even under strongly-colored lighting, the camera produces image
files with plenty of data in all three color channels, making
it fairly easy to clean up the images in an image-editing program
after the fact.
Flash
The PowerShot A50's built-in flash is fairly typical in its capabilities,
providing auto, always-on, always-off, and red-eye reduction
modes. It has a range of 8 feet (2.5 meters) with the lens at
the wide-angle end of its range and 11.5 feet (3.5 meters) at
the telephoto end. It also throttles-down very well for shooting
in macro mode, with Canon rating it for use all the way in to
6.7 inches (17cm). This agreed with our own experience. We did
find in our own experimenting with it that it's worthwhile to
play with the white-balance settings when using flash in conjunction
with strong artificial ambient lighting -- Often, using a manual
white-balance setting along with the flash will produce more
pleasing results than the auto option.
Like most digicam internal flash units, the strobe on the PowerShot
A50 fires twice for each shot: A pre-flash to determine exposure
and white-balance settings, and then a second time for the actual
exposure itself. Thus, you'll need a special slave-sync (such
as the unit from SR Electronics) that triggers on the SECOND
flash, to synchronize external strobe units with it.
Shutter Lag Time/Cycle Times
When you press the shutter release on a camera, there's usually
a lag time before the shutter actually fires. This time is to
allow the autofocus and autoexposure mechanisms time to do their
work, and can amount to a fairly long delay in some situations.
Since this number is almost never reported on, and can significantly
affect the picture-taking experience, we now routinely measure
it. (Using a hand-tweaked animated GIF image providing an on-screen
count-down in tenths of a second.)
The A50 had a bit longer shutter lag than most digicams we've
tested, depending somewhat on the camera/subject distance. At
greater distances (where the lens mechanism had less distance
to travel to achieve proper focus), shutter lag was about a second,
very much on a par with other cameras we've tested. On the other
hand, when the subject was much closer (a couple of feet, for
instance), the shutter lag increased to about 1.6 seconds. When
the camera was pre-focused by half-pressing the shutter button
prior to the exposure itself though, the shutter delay dropped
to only 0.2 seconds for all cases, a pretty typical performance.
The other important time interval in digital photography is the
cycle time, the minimum time interval between successive exposures.
The A50 performed quite well in this respect: It appears to have
a fairly sizeable RAM buffer to help it process images quickly.
We measured the minimum cycle time at roughly 4 seconds for large/fine
pictures, decreasing to about 2 seconds for small/coarse pictures.
These are very respectable times for a 1.3 megapixel digicam!
Overall, the PowerShot A50 is about as responsive to the shutter
control as other digicams, except at rather short camera/subject
distances. Picture-to-picture cycle times are better than most
other competing cameras.
Other times: Startup - ~5.8 seconds. Switch to play mode,
high-res picture ~11 seconds. Shutdown ~ 4 seconds.
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