Canon PowerShot A550

Color (9.58)
Canon digital cameras have typically performed well in this test, so we had high expectations for the A550. We ran the Canon A550 through the same regimen as all other digital cameras that come through our lab and review process. Using optimal studio lighting, we photographed the GretagMacbeth color chart at ISO 80.

After some experimentation, the picture with the most realistic colors came from a shot using a -1 exposure compensation setting in spot metering mode. Imatest software analyzed the shots from the color test. The program compared the colors from the PowerShot to those of the original GretagMacbeth chart. The chart below, modified by Imatest, shows the ideal colors as vertical rectangles, the camera’s colors as the outer portion of the squares, and the luminance corrected ideal color in the central portion of the squares.

Below is another chart that shows the degree of error in colors. The squares represent the ideal colors of the chart and the circles represent the colors produced by the Canon PowerShot A550.  

The most inaccurate colors are the warmer reds, but most colors are closely tethered to where they ought to be. The mean color error was a low 6.26 resulting in an excellent 9.58 overall color score. The saturation is close to perfect at 105.3 percent. This is right on with other PowerShot digital cameras.  

White Balance (8.52)
Auto (8.27)
We pitted the automatic white balance setting against all the presets and most of the time, the automatic setting came out more accurate. This is a bit surprising since the all-purpose settings don’t always serve all purposes. The auto white balance setting was more accurate than all of the presets except in tungsten light, when the preset performed far better. Overall, the automatic white balance setting is far more reliable than many competing models and recommended for use except when indoors under tungsten lights.

Auto WB - Tungsten Illumination

Auto WB - Shade Illumination

Auto WB - Flourescent Illumination

Auto WB - Flash Illumination

Preset (8.76)
As stated previously, the automatic setting is quite reliable except in tungsten lighting where the preset mode performs more accurately. The only other area where the camera struggled was in the shade, where both the automatic and preset white balance settings cast an unnatural blue tint.

Fluorescent WB - Fluorescent Illumination

Shade WB - Shade Illumination

Tungsten WB - Tungsten Illumination

Still Life Sequences
Below are two still life sequences shot with the A550 across its ISO range.

Click on any of the thumbnails below to view the full resolution images.

Still Life Scene
ISO 80	ISO 80
ISO 100	ISO 100
ISO 200	ISO 200
ISO 400	ISO 400
ISO 800	ISO 800

Resolution (5.83)
The Canon PowerShot A550 outdoes its predecessors with more resolution packed onto its 1/2.5-inch image sensor. It advertises 7.1 megapixels. We tested its effectiveness by photographing an industry standard resolution chart at various focal lengths and apertures. Imatest imaging software analyzed all of the images and selected the sharpest shot, snapped at 18mm and f/5 and using the lowest ISO 80 setting.

Click to view high-resolution image

Imatest output resolution results in terms of line widths per picture height (lw/ph), a unit that describes how many alternating black and white lines of equal thickness could fit across the frame without blurring. The Canon A550 can resolve 1609 lw/ph horizontally with 7 percent oversharpening and 1697 lw/ph vertically with 6.95 percent undersharpening. These results are decent especially for a compact digital camera in this price range.

Noise – Auto ISO (1.40)
Most users of this digital camera will likely opt for the automatic ISO setting, but they should reconsider. We set the camera to automatically choose a sensitivity and it selected ISO 200, which was more than what was necessary under the bright lights of the studio. Way too much noise was present at the camera's ISO 200 setting, resulting in an awful 1.4 auto ISO noise score.

Noise – Manual ISO (3.81)
For this test, we photographed the color chart at the available manual ISO settings from 80 to 800 and analyzed the images for noise. Below is a chart showing just how much noise resides at each setting. The ISO settings are on the horizontal axis and the percentage of the image marred by noise is on the vertical axis.

The Canon PowerShot A550 has a bit less noise than its predecessors and an extra ISO stop too. The noise jumps leaps and bounds from one ISO setting to the next, so users should try to keep it as low as possible to snap clean pictures. After analyzing the data and putting the results into a regression analysis, the overall manual ISO noise score came out to 3.81. This certainly isn’t great, but it is better than the automatic setting and is typical of budget digital cameras.

Low Light (5.62)
Because candlelight weddings are in style and restaurants dim the lights to enhance ambience, photographers need to know how their cameras will react when the lighting is less than ideal. We dimmed the lights in our studio to simulate a softly lit room with two shaded lamps (60 lux) and a darker room with only a single 40-watt bulb (30 lux). We also tested the Canon PowerShot A550 at 15 and 5 lux to see how the image sensor would react.

Low Light Tests
60 Lux	30 Lux
15 Lux	5 Lux

Illumination remained fairly constant and color accuracy remained remarkably in tact. At the darkest 5 lux, the mean color error only slipped to 6.64 which is still better than most cameras in perfect lighting. The Canon A550 performed very well in our low light test at its higher ISO settings.

Dynamic Range (5.36)
We tested how well the Canon PowerShot A550 could handle bright and dark areas in the same image by photographing a backlit Stouffer test target film. There is a row of rectangles on the film that range from bright to dark and represent about 13 exposure values, which is more than most digital cameras can accurately represent at once.

We uploaded the A550’s images of this chart into Imatest, which determined how many exposure values the camera can record at once. The chart below shows the exposure values on the vertical axis and the manual ISO settings - which affect the dynamic range - on the horizontal axis. There are two levels of quality plotted. The high quality measures steps of range with a tenth a stop of noise, while the low quality measures steps with up to a full stop of noise.

At the lowest ISO settings, the Canon A550 captured about 8 exposure values, but there is a major drop in dynamic range from ISO 200 to 400. This performance is mediocre when compared to similar budget digital cameras. What should users learn from this? If shooting in a high contrast scene, it's best to try to keep the ISO above 200.

Speed/Timing
Startup to First Shot (8.2)
Canon has improved its digital cameras in this area. The Canon A520 took nearly 3 seconds to start up, but the new A550 takes only 1.8 seconds to start up and take its first picture. This is great for a budget digital camera, but it still isn’t close to the world’s fastest.

Shot-to-Shot (9.4)
The Canon PowerShot A550 has a decent burst mode when compared to other digital cameras in this price range. This camera took a picture every 0.6 seconds and did so up to the memory card’s capacity: 250 shots in this case. The shots are processed immediately too, so there is no waiting at the end of a burst to start another batch of pictures like on most other digital cameras.

Shutter-to-shot (8.2)
The old A520 took 0.71 seconds to take a picture, so there is some improvement on the new model. Still, the 0.4-second shutter lag is disappointing to users who try to snap candid pictures and end up with turned heads and closed eyes.

Processing (8.4)
Pictures are processed immediately during the burst. In the continuous shooting mode, the camera takes a shot every 0.6 seconds and stores it in that time too.

Video Performance (3.91)
Bright Indoor Light (3000 lux)
We recorded a few videos of test charts in our studio using the auto settings and uploaded them to Imatest, which analyzed it just as it does still pictures. The results were a bit disturbing. In the bright lights of the studio, the colors were horribly erroneous with a tragic mean color error of 23. Not only are the colors completely off but the saturation compounds at 132.9 percent. The amount of noise present isn’t impressive either at 0.5425 percent of the image.


Low Light (30 lux)
Using the same settings, the mean color error surprisingly returns within normal range in low light. The mean color error of 9.08 is only a bit worse than the still image’s performance in comparable light. Colors are undersaturated at 82.47 percent. As with most cameras in low light, the amount of noise in the video increased to 2.335 percent of the image.


Resolution
We recorded a 640 x 480-pixel video of a resolution chart and uploaded it to Imatest, which outputs results in the same line widths per picture height (lw/ph) unit used in our still image resolution test. Horizontally, the Canon A550 resolved 251 lw/ph with 19.1 percent undersharpening. Vertically, it resolved 340 lw/ph with 10.6 percent oversharpening. These numbers are typical of compact digital cameras’ movie modes.

100% Crops

Outdoor Motion
We went outside to get some fresh air and toted the Canon PowerShot A550 out for a few "real world" videos. We recorded a few clips of moving cars, dogs, strollers, and the hustle and bustle of the city streets and observed a few things. The video retained good contrast, but the edges of the frame were softer than the center. Moving subjects stuttered a bit too even though the camera records 30 fps. Still, the Canon A550 performed better than most digital cameras in this area.

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