Canon PowerShot A570IS Digital Camera Review
Read a digital camera review of the Canon PowerShot A570 IS, which features image stabilization, on DigitalCameraInfo.com.
Testing / Performance
The Powershot A570IS delivers excellent color – its results are better than many professional-level cameras. We measure the accuracy of cameras' saturation and color, and the A570IS is stellar on both counts.
We test color by photographing a GretagMacbeth color chart, and using Imatest software to measure the results. Imatest produces numerical results as well as two charts. The first chart shows the camera's image of the GretagMacbeth target. The big squares show the colors as the camera captured them. The smaller squares show the original colors, corrected for luminance, and the smallest shows the ideal color.
Imatest's other chart plots the GretagMacbeth colors on a color gamut chart. The ideal color is plotted with a square, and the camera's color with a circle. The length of the line between each circle and square indicates the amount of error. If the circle is further from the center of the chart than the square, the camera's color is oversaturated. If it's clockwise or counterclockwise from the square, then the hue is wrong.
The PowerShot A570IS's circles are very close to the squares – some land perfectly, right on top of the squares. Compare this chart with the same chart for other cameras – this one is much, much better than typical.
White balance controls adjust cameras to the color of light cast on a given scene. Outdoor shade is blue, lightbulbs cast relatively orange light, and so on. The Canon PowerShot A570IS's automatic white balance feature works best with the camera's built-in flash. In other kinds of light, it delivers less accurate results, but compared with other point-and-shoots, it delivers equally pleasing color.
The PowerShot A570IS's white balance presets gave excellent results. They are considerably better than the Auto setting for everything except flash and fluorescent. Fluorescent is always problematic, because it comes in so many varieties, and the tubes change color as they age. So, the A570IS's results weren't great with either the preset or the auto setting.
**Still Life Scenes
**Click to view the high-resolution image.
*Resolution measures how much detail a camera can record, and we test it with Imatest software, the industry standard for evaluating digital image quality. We photograph an industry-standard resolution chart with the camera mounted on a heavy studio tripod. We test each camera at several zoom settings and apertures, and report the best results. The A570IS did best at 13mm and f/6.3, but its results are disappointing. It resolved 1794 line-widths per picture height horizontally, with 11.4 percent oversharpening, and 1656 lw/ph vertically, with 12 percent undersharpening. Line-widths per picture height is a unit of measure for resolution that describes camera performance in a way that can be compared between cameras with various sensor sizes.
Oversharpening is a problem common to snapshot cameras, and the A570IS shows it in the horizontal axis. All digital cameras process and sharpen their images as they save the files. Oversharpening can show up as halos and blotches in pictures, while undersharpening simply limits the amount of detail in an image. Either way, even a point-and-shoot should have sharpening figures within 10 percent of ideal, which the A570IS came close to but did not quite meet.
Noise – Auto ISO*(1.74)
*Image noise is a lot like audio noise. When two people try to talk in a loud factory, the thing that prevents them from hearing each other is noise. For engineers, noise is anything that degrades a signal – the sounds of machinery in a factory, for instance, is noise, for people trying to talk. What they are saying is the signal.
The picture is the signal in a digital camera. The electronics that capture and process the image aren't perfect, so they add noise to the signal, and the noise looks like light and dark speckles or wrong colors. Imatest measures noise from images of the GretagMacbeth color chart.
With its ISO control set to Automatic, and in bright light, the PowerShot A570IS delivered noise scores as if the ISO were set to 200. The A570IS's noise performance is better at 80 and 100, so it should have used ISO 80 in bright light.
Noise – Manual ISO*(4.01)*
The PowerShot A570IS is not a low-light camera. The noise levels are acceptable from ISO 80 to 200, but they take a big jump at ISO 400, and keep rising steeply at 800 and 1600. Users should avoid going over 200 unless they can't get the shot without higher ISO. The noise level at 1600 produces images that are obviously low-quality, even at small sizes. The image noise at higher ISOs shows up with light and dark speckles, and oddly-colored spots (see color charts below).
Our low light tests use the GretagMacbeth chart, We photograph it in 60, 30, 15 and 5 lux of light. 60 lux is enough to read by. In a room lit at only 5 lux, it's hard to see the furniture.
The PowerShot A570IS has an automatic noise reduction algorithm for long exposures, which helps. Still, most users will want to use high ISOs in low light, and image noise will be a problem for them. On a positive note, the A570IS maintains good color accuracy at low light levels and in long exposures, with mean color errors of 8.07 at 5 lux, and 6.7 in a 15 second exposure.
*Dynamic range describes the range of brightness that a camera can record while maintaining detail and limiting image noise. We test it by shooting a Stouffer step chart, which shows a series of rectangles that run from light to dark. They range more than 13 EV in brightness. We use Imatest to show how much of that range a camera reveals.
Again, the dynamic range test shows that the PowerShot A570IS performs significantly better at its minimum ISO of 80 than at 100.
At ISO 80, the A570IS records just under 7 EV, which is respectable for a compact camera. At 100, though, it drops to about 5 EV, which is a poor score at that setting. At 400, it's in the range of 3 ½, which is lousy, and at 800 and 1600, it has scores under 3 and 2 EV, respectively. The results at 800 and 1600 would be obviously bad, for even the most casual user.
Sometimes, our reviews report shortcomings that are common to all cameras in a class, but in this case, the A570IS is particularly bad – nearly all cameras do better than this.
***Startup to First Shot (8.0)*
It took 2.0 seconds after the PowerShot A570IS was turned on for it to rouse itself and get off a shot after being turned on. That's a long time, for users who turn on their cameras during a brief photo opportunity, but it is typical of cameras that have to extend their lenses.
In burst mode, the PowerShot A570IS shot every 0.75 seconds until the memory card was full. That works out to 1½ frames per second, which is not fast enough to get more than one or two shots of quick events, like a child blowing out birthday candles. It's not nearly fast enough for sports action or wildlife, but that's not what the camera is designed for. More expensive compact cameras offer faster burst modes. A 3-frame-per-second burst mode, which is available on many cameras, is noticeably more useful than 1½.
Most digital cameras can pre-focus – press the shutter halfway, and the autofocus mechanism operates, and stays focused until the shutter is pressed all the way. With pre-focusing, we could not detect any delay at all from the PowerShot A570IS. In contrast, without pre-focusing, it took the A570IS 0.4 seconds after the shutter was pressed to take a picture. That length of delay makes it very hard to get shots of moving subjects; in focus or not, it can be hard to even keep them in the picture for that length of time.
The A570IS takes 0.6 seconds to process a shot and record it to its SD card. This speed is faster than the burst rate, so the processor never falls behind the shooting rate. Other cameras can shoot faster than they process, and after anywhere from 3 to 100 shots, they have to stop shooting, so that the processor can catch up.
*Bright Indoor Light - 3000 lux
*The PowerShot A570IS's video image quality is inferior to its still image quality by a ghastly margin. First, let's look at bright light performance. At 23.3 percent, video color error is 5 times worse than still color error. The saturation score of 137.3 percent for video is about 15 times worse than the still score. Because the video image has such low resolution, the noise score looks pretty good; it's 0.52 percent. All told, the color is oversaturated on the scale of a comic book, and all of the colors are smeared toward the orange range.
Low Light - 30 lux
In low light of 30 lux – similar to the light in a living room at night – mean color error drops to 10.1 percent, probably because saturation has dropped to 80.13 percent, and average noise is up to 2.42 percent. The image looks dull and gloomy. On the Imatest color chart, pairs of circles, which show the camera's color, clump together because the A570IS's video mode can't distinguish between the GretagMacbeth swatches.
Standard video is 640x480 pixels so the PowerShot A570IS's horizontal resolution of 244 line widths per picture height and vertical resolution of 374 LW/PH seem within the ballpark for casual video. The A570IS undersharpens by 22.8 percent on the horizontal scale and oversharpens by 12.4 percent on the vertical scale. It's not unusual to see a disparity between the two sharpening scores, but one is too high and the other is way too low. This difference explains some of the poor numbers for resolution.
As digital video is recorded, one of the compression options is to carry over unchanged pixels from frame to frame. This can result in jerkiness if the camera saves pixels too long. The PowerShot A570IS avoids this pitfall, with smooth motion in our outdoor shots. The only problem with jerkiness we saw was as objects moved out of the frame, which is the most challenging kind of movement for these systems. Compared with other still cameras' video modes, the A570IS handles motion well.