Color (9.65)
We evaluate each camera’s color performance based on the accuracy of the reproduced tones when contrasted with the original values of an industry standard GretagMacbeth color chart. It is important to note that many people will often prefer a more saturated and less accurate image to a realistic representation; however, it is far easier to add saturation to the various color channels after the image has been captured than to try to edit the image back to the natural scene.
To test how accurately the A520 reproduces colors, we capture a sequence of exposures of the GretagMacbeth color chart, which has become accepted as a standard measure of ideal colors, under controlled lighting and import the files into Imatest Imaging Software. The software is used to read the images and determine how accurate each rendered tone is compared to the corresponding ideal. The chart below displays the results; for each color tile, the outer square is the camera’s reproduced color, while the vertical rectangle is the ideal. The inner square approximates how the camera’s produced tone might appear following color correction.
The same information is again displayed in a more linear graph below. The squares depict the colors produced by the PowerShot A520, while the circles represent the ideal. The line linking the two expresses the degree of error for that particular tone – the greater the distance between the related shapes, the less accurate the camera’s reproduction of that tone.
The A520 performed remarkably well on our color tests. Most rendered tones were “spot on” the standard, with the only variance in #4 (“foliage”), #9 (“moderate red”), #17 (“magenta”), #15 (“red”), #7 (“orange”), and #12 (“orange yellow”). This is impressive because all of the colors that stray from the ideal seem consciously designed that way. Most camera engineers understand that a majority of people are drawn to vibrant images that do not necessarily look realistic but seem to have an idealized quality. To cater to this appeal, most camera designers embellish red and pink hues to smooth out “skin tones” as well as some green values to glorify landscapes. Referring to the chart above, it appears that all of the A520’s produced colors that stray from the ideal are related to portraiture or scenery shots and the rest of the color values are nearly perfect. This color orientation is sure to satiate most snapshooters and is as strong as any sub-$300 camera I have seen.
Still Life Scene
Below is a shot of our cutting-edge still life scene photographed with the Canon PowerShot A520.
Click on the above image to view a full resolution version (CAUTION: the linked file is very large!)
Resolution (2.69)
The A520 is advertised by Canon with 4.3 total megapixels on the camera’s 1/2.5-inch CCD, 4.0 of which are effective for imaging. To test resolution of the A520’s imaging sensor, we record an abundance of images of an ISO resolution chart and import the results into Imatest Imaging Software. The shots are taken under controlled lighting, at various focal lengths and aperture settings, with the camera’s highest score reported. The scores are reported as both literal pixel count and a percentage of the advertised resolution. When this is conducted, cameras that score beyond 70 percent of their marketed resolution are deemed “good,” while those exceeding 80 percent are viewed as “very good.” Cameras that exceed 90 percent are “excellent” and quite rare.
Click on the above chart to view full res. image
While the A520 did not prove itself a rarity, it performed just shy of the “good” plateau, capturing images with 69 percent of its marketed capabilities or 2.69 active megapixels. This is a decent score when contrasted with other similarly priced models and should not deter users from purchasing the camera unless large prints are sought. Users should feel confident making 8 x 10 prints with the A520 so long as no cropping is going to be done. If larger prints are desired, consumers will have to shell out more than $300.
Noise – Auto ISO (6.76)
While the A520 does offer a hefty selection of manual controls, many users will still likely rely on the Automatic setting. We test the auto ISO setting for noise under studio lights exceeding 400 lux of illumination. In this test, the A520 produced images that were remarkably clean. Perhaps surprising to some, the A520 earned a relatively high 6.76 auto ISO score but still fell well short of the PowerShot A510’s 9.6 auto noise score. The two cameras are virtually identical other than their sensors; the A520 contains a 1/2.5-inch 4.2 megapixel CCD sensor, while the A510 has a 1/2.5-inch 3.2 megapixel CCD. While many consumers shop for resolution, the truth is, it can often work against image quality.
Resolution is measuring definition and sharpness; however, noise is not necessarily a variable in that equation but does significantly impact image quality. Think of the difference between a 7.2 megapixel compact camera and a 6.1 megapixel DSLR; while the compact camera contains more resolution, the DSLR will consistently produce higher quality images. The reason for this is that the DSLR contains pixels on the sensor, resulting in far less noise. This is why many 7 megapixel compact cameras have such difficulty with noise at higher ISO settings. Therefore, the A520 should present more of an appeal to users who want printing flexibility and the opportunity to crop their images. For those who are going to be printing small and are more concerned with clean images with increased quality, they should opt for the A510.
Noise – Manual ISO (3.77)
Continuing with noise evaluations, the A520 contains the same sensitivity options as the less expensive A510. Both cameras offer Auto, 50, 100, 200, and 400 ISO options and both have the same size imaging sensor. The A510 earned a 6.0 overall manual ISO score when each sensitivity option was tested for noise. In all likelihood, the A520 won’t reach that mark, but hopefully will perform similarly.
To test this, we took a series of images of our GretagMacbeth color chart at each available ISO setting and imported the results into a regression analysis to determine an overall noise score. The chart below expresses the results, with the noise levels graphed on the vertical Y-axis, while the available ISO settings are plotted on the horizontal X-axis.
The A520’s performance was a bit surprising, producing images that were significantly more noisy than its less expensive counterpart. Again, some slight reduction in quality was expected; however, the difference was substantial. The A520 earned a 3.77 overall manual noise score with images becoming unavoidably flawed at ISO 200, while the A520 scored a 6.0 overall score and did not become overwhelmingly compromised until the ISO 400 setting. The difference cannot be ignored. Users who are thinking about purchasing a new PowerShot model and are considering upgrading to the A520 because of image quality, think again.
Low Light Performance (5.5)
We test the low light capabilities of each camera we review at decreasing light values to observe the camera’s ability to perform at night or in compromised indoor situations. The cameras are tested at 60, 30, 15, and 5 lux to approximate its performance in typical low light conditions; 60 lux appears to the eye as a room might when lit by just 2 small table lamps, while 30 lux is similar illumination to a single 40 watt lightbulb, and 15 and 5 lux provides some insight to the camera’s ability to record in near darkness.
On point-and-shoot cameras, we typically test for low light using the camera’s Auto or Program Auto setting, as this will likely be the mode of preference for the majority of users. Since the A520 fits into an old category of user control within the compact camera market, it is not quite as clear which mode will appeal to the majority of users.
Given the size and price of the A520, we opted to test the camera’s low light capabilities using the PROGRAM Auto setting. While the camera offers a substantial degree of user control, those carrying the camera in their shirt pocket will often just point and shoot. Therefore, we decided to test the sensitivity of the CCD to light using the program auto setting, knowing that those users who want to get more out of the camera will have the option to do so. Thus, unlike our previous tests, these results are NOT the best users can get out of the camera, but rather is measuring what the camera will do without assistance from the user. Users who want better low light images from the A520 can attain them with the camera, but will have to bring along a tripod and set the shutter speed down to 15 seconds, which is also a bit limiting.
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Low Light Tests
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60 Lux
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30 Lux
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15 Lux
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5 Lux
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Click on any of the charts above for additional image analysis
As you can see from the low light images captured with the A520, when set to its Program Auto setting images are not very flattering. The camera’s imaging sensor is not extremely sensitive, so users intent on capturing an elegant night skyline should plan ahead, set the camera on a tripod and use the manual setting to leave the shutter open for as long as is necessary (up to 15 seconds). When set to auto or program mode, the camera will handle 60 lux, but still, image quality is compromised. The colors lose accuracy and become muddy. Noise will be rampant, but unfortunately, that is unavoidable with the A520 when set on its ISO 400 setting. The camera can be manipulated to perform beyond the images above, but not much. If low light images are sought, consumers should look into other alternatives with higher sensitivity options.
Speed / Timing
Start-up to First Shot (7.08)
The A520 is certainly not up to speed with the current compact camera market, as many manufacturers seem to be emphasizing performance rate among point-and-shoot models as well as higher-end cameras. The A520 retains the DIGIC imaging processor rather than including the DIGIC II which would have made the camera significantly faster. The A520 required nearly three full seconds to start up and capture its first image. Therefore, those eager shooters should have the camera powered up and waiting.
Shot to Shot Time (9.1)
The A520 is a bit faster once it is up and running and will record subsequent frames in just less than a second. Unfortunately, there is a limited buffer, so use the limited speed wisely.
Shutter to Shot Time (7.58)
Shutter lag is a serious objection for many users, creating a bit of an argument for consumers to stay with film cameras; however, digital manufacturers have taken notice and begun to minimize the delay. The A520 takes just over .71 seconds from the time the user depresses the shutter to the time the image is captured, but this is still pretty slow compared other some point-and-shoot models that require less than .1 second.
