Canon PowerShot A650 IS

Color (12.3)
Ideally, a camera will reproduce colors as accurately as possible, making them look vivid, but natural. We test color accuracy by photographing a GretagMacbeth ColorChecker test chart and comparing the colors the camera reproduces with the known colors of the test chart. The ColorChecker is made of 24 different color tiles from around the color spectrum. The image below shows how the Canon A650 IS’s colors compare to the test chart. The outer squares show the colors the camera reproduces, the inner squares show the actual colors of the ColorChecker corrected for exposure, and the small rectangles show the ColorChecker colors under a perfectly even exposure.

Most of the outer squares blend into the inner squares, showing how accurate the A650 IS’s colors are. The small rectangles appear lighter than the squares because the A650 IS’s colors are more accurate when slightly underexposed. The only colors that seem a little inaccurate are the yellows and blues. The graph below shows color accuracy in a different way. The locations of the ColorChecker color tiles are shown as squares on the color spectrum, and the corresponding colors the camera reproduces are shown as circles. The lines connecting the squares and circles show the extent of the color error.

The graph confirms that the A650 IS’s colors are extremely accurate, as demonstrated by how close the circles are to the squares. The only colors with some "drift" are yellows and blues. These colors are often shifted on purpose to enhance blue skies and green foliage. Overall, the A650 IS has fantastic color accuracy, making colors look natural and vivid at the same time.

Resolution (9.49)
We test resolution by photographing an industry standard resolution test chart at a variety of settings to find which settings produce the sharpest image. We use Imatest to analyze sharpness and amount of sharpening applied to an image by the camera. Imatest measures sharpness in terms of line widths per picture height (lw/ph), which refer to the number of equally spaced, alternating black and white lines that could fit across the picture frame without blurring.

The 12-megapixel Canon A650 IS is sharpest at ISO 80, f/5.6, and a focal length of 19 mm. The camera resolves 2194 lw/ph horizontally with 7.7 percent oversharpening, and 1958 lw/ph vertically with 17 percent undersharpening. These are very impressive numbers, and show the camera’s optical system produces sharp images without too much sharpening being applied by the processor. However, images are slightly blurry and a fair amount of chromatic aberration is apparent in the corners. Yet overall, the A650 IS is one of the strongest performers in this test this year. It is a great choice if you plan to make large prints of images shot at low ISO speeds.

Noise – Manual ISO (4.44)
Image noise refers to the sandpaper effect you sometimes see in photos taken in low light or at high ISO speeds. We evaluate noise levels by photographing our test chart at all ISO speeds a camera offers. We run the photos through Imatest, which measures noise in terms of the percentage of image detail it drowns out.

The A650 IS keeps noise levels low at ISO 80 and 100, but loses control at higher ISO speeds, where photos look like they were taken in a sandstorm. This is one of the main problems with cramming 12 megapixels on a sensor; more pixels means smaller pixels, which produce more noise. The noise itself looks very sandy and granulated, with small splotches of blue and yellow spread throughout. It isn’t the ugliest noise we’ve ever seen, but there is enough of it at high ISO speeds to ruin photos. Keep this camera at low ISO sensitivities as much as possible.

Noise – Auto ISO (1.35)
We also test noise levels with the camera set to Auto ISO, under the same bright studio lights as above. The A650 IS chose ISO 200, yielding more noise under such bright light than we would like to see. This noise will be visible when viewing photos at full size.

White Balance (13.63)
The A650 IS’s excellent color accuracy would be irrelevant if the camera couldn’t white balance properly. White balance is important because all types of light sources have different color casts, and a camera must be able to adjust accordingly. We test white balance by photographing the ColorChecker test chart under four different types of light: flash, fluorescent, outdoor shade, and tungsten. We test both the auto white balance setting and the appropriate white balance presets.

Auto (12.30)
Using the auto setting, the A650 IS very accurate in fluorescent light, outdoor shade, and the flash, but poorly accurate under tungsten light. These are great results, and show that you can leave this camera on auto white balance in most situations except for indoor tungsten light, where almost all cameras have difficulty.

Preset (15.00)
With the white balance presets, the camera is also extremely accurate. Every type of light source scored very well in color accuracy using the presets. If you take a photo that seems to have a color cast to it, simply switch to the white balance preset and it should correct the problem.

Low Light (7.96)
Not all shooting will be done in bright lighting, so we also test color accuracy and noise levels in low light. To do this, we photograph the ColorChecker test chart at light levels of 60, 30, 15, and 5 lux. 60 lux is about as bright as a room lit softly by two table lamps, 15 lux is as bright as a room lit solely by a 40 watt bulb, and 15 and 5 lux are quite dim and test the limits of the sensor. All shots are taken at ISO 1600.

The A650 IS has no problem exposing at any of these light levels, and also keeps colors very accurate. Noise levels, however, are off the charts, and make photos look like sandpaper. If must take photos in low light with this camera, you should put the camera on a tripod and use the lowest possible ISO speed.

We also examine low light performance using slow shutter speeds, this time at ISO 400. This test shows that the A650 IS can also keep colors accurate in long exposures, but photos will still be affected by noise. Still, the image quality is good enough to stand up to long exposures.

Dynamic Range (4.74)
Dynamic range is another factor that affects image quality. . Dynamic range affects how much detail a camera can discern in high contrast scene. A camera with good dynamic range will maintain details in bright highlights and dark shadows in an image. We test dynamic range by photographing a backlit Stouffer step chart, which consists of a long row of gray rectangles ranging in brightness from bright white to dark black. The more rectangles a camera can distinguish, the better its dynamic range.

The A650 IS has great dynamic range at ISO 80, but fairly disappointing dynamic range at higher ISO speeds. The camera’s high noise levels are a big factor in this, because the noise drowns out image detail in dark areas of photos. This is another reason to leave the camera at low ISO speeds as much as possible. The A650 IS scores poorly in dynamic range.

Speed/Timing – All speed tests were conducted using a Kingston Ultimate 120X 2GB SD Card, with the camera set to highest resolution and best quality, unless otherwise noted.

Startup to First Shot (7.9)
The A650 IS takes 2.1 seconds to take a photo after it has been turned on.

Shot-to-Shot (9.0)
The A650 IS has one continuous Record mode, in which it will take 3 photos 0.8 seconds apart and then shoots indefinitely every 1.1 seconds.

Shutter-Shot (9.0)
The camera has no measurable lag when it has been prefocused, but a lag of 0.5 seconds when it hasn’t been prefocused.

Processing (5.2)
The A650 IS takes 2.2 seconds to process one 2.2 MB full size image, with the camera set to superfine compression and ISO 160.

Video Performance (4.49)
Bright Light – 3000 lux
We capture footage of our video charts under bright studio lights to see how the camera renders colors and noise. The A650 IS as tremendous color error using auto white balance, but low noise levels.

Low Light – 30 lux
In low light, the video has far more accurate colors, but significantly more noise. The camera’s Movie mode certainly doesn’t replace a camcorder, but it should allow users to take decent videos in dimly lit situations.

Resolution
When aimed at the resolution chart, the A650 IS resolved 317 lw/ph horizontally with 6.8 percent undersharpening, and 455 lw/ph vertically with 21 percent oversharpening. These are decent numbers for digital camera video, but not anything special.

Outdoor Motion
We shoot video outside to see how cameras handle the motion of cars and pedestrians. The A650 IS’s Movie mode has nice looking colors and good detail, but suffered from moiré, overexposure, and some jerkiness when objects move off the frame. Overall, the camera has a decent Movie mode, but not quite as good as some of its competitors.