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Every camera shifts colors a bit, whether purposely or accidentally. Sometimes colors are oversaturated on purpose to make them "pop," but at the expense of looking unnatural. Sometimes colors are undersaturated, yielding, for example, very pale-looking portraits. We test color accuracy by photographing an industry standard GretagMacbeth ColorChecker test chart and comparing the colors the camera reproduces with the known colors of the chart. The ColorChecker chart is made up of 24 color tiles from around the color spectrum. The chart below shows how accurately the A720 IS reproduces the colors of the ColorChecker chart. The outer squares show the colors the A720 IS reproduces, the inner squares show the actual colors of the chart corrected for luminance, and the inner rectangles show the chart colors at a perfectly even exposure.
Many of the inner squares blend into the outer squares, showing how accurate the A720 IS’s colors are. The few tiles that are off are the yellows and one of the blues. The graph below shows color accuracy in a different way. The background of the graph shows the entire color spectrum, and the colors of the ColorChecker chart are represented by squares, while the colors the A720 IS reproduces are shown as circles. The lines connecting the squares and circles show the amount of color error for each tile.
The graph confirms the camera’s impressive color accuracy. Most of the colors are dead-on. The few that drift are the yellows that are shifted toward green, and the saturated blue that is shifted purple. These colors may be shifted on purpose to enhance landscapes, making sky blues more vivid and foliage stand out. Though the few inaccurate colors may have unwanted effects, overall the A720’s color accuracy is excellent.
**Resolution ***(6.88) *
We test resolution by photographing an industry standard resolution test chart at varied focal lengths, apertures, and shutter speeds. We run the images through Imatest to find the settings that produce the sharpest images. Imatest measures image resolution in units of line widths per picture height (lw/ph), which refer to the number of alternating black and white lines that can fit across the image frame both horizontally and vertically.
The 8-megapixel A720 IS has the best resolution at ISO 80, f/4.0, and a 17.2mm focal length. The camera resolves 1770 lw/ph horizontally with 6.6 percent oversharpening, and 1644 lw/ph vertically with 5.9 percent undersharpening. These numbers are very solid, and perhaps most importantly, the sharpening levels are very reasonable. Too much sharpening can often cause unwanted side effects, which are mostly absent from the A720 IS’s wide aperture photos. The only issue with this camera’s resolution is that the corners are slightly blurred. Other than that, the resolution is very good, and should allow users to make fairly large prints.
Noise – Manual ISO*(5.17) *
Image noise, comparable to TV static or stereo hiss, is an unavoidable consequence of digital imaging. In digital cameras, noise takes the form of sandy grains or small splotchy patches randomly scattered throughout a photo. Noise is always higher at higher ISO speeds, because when sensitivity is boosted, noise is amplified. We test noise levels by photographing our test chart under bright, even studio light at all ISO speeds the camera offers. We run the photos through Imatest, which calculates noise levels by the percentage of image detail the noise drowns out.
The A720 IS keeps noise levels low at ISO 80 and 100, but at higher ISO speeds noise becomes much more apparent. At ISO 800 and 1600 noise is blatantly obvious and overwhelms the photos. The noise itself is very ugly, full of small white specks, and larger blue and yellow splotches. At ISO 800 and 1600 the images even look a little smoothed, which is a method used to make noise levels lower. The smoothing just hurts image detail however, and noise levels are still very high. Overall, noise levels are worse than the 2007 point-and-shoot average, and much worse than competing models such as the Fuji FinePix F40fd and Panasonic Lumix TZ3.
**Noise – Auto ISO ***(1.5) *
Using the same bright studio lights, we test noise levels with cameras set to Auto ISO. The camera chose ISO 200, but had disappointingly high noise levels. With this camera it pays to keep the ISO as low as possible, especially if you are thinking of cropping images or making large prints.
**White Balance ***(13.38)
*Without proper white balancing, a camera cannot have good color accuracy. Every type of light has a different color cast to it, and a camera must be able to adjust accordingly. We test color accuracy by photographing the ColorChecker test chart under four different types of lighting: flash, fluorescent, outdoor cloudy, and tungsten. We test the camera’s accuracy using Auto white balance as well as the appropriate white balance presets found in the Function menu.
When set to Auto white balance, the A720 IS is extremely accurate under flash, fluorescent, and outdoor cloudy light. Under tungsten light, however, accuracy is very poor. Cameras are often very inaccurate in tungsten light, however, and the accuracy of this camera in other types of light is fantastic. This is a camera you can leave on Auto white balance and know your colors will stay extremely accurate — except in tungsten light, of course.
*Even though the Auto white balance is extremely accurate, using the presets is just as good. The Cloudy, Fluorescent, and Tungsten presets are all very accurate, and this is especially useful because the Auto setting is poor under tungsten light. In short, the camera can be left on Auto white balance with fantastic results, unless you find yourself shooting indoors under tungsten lights, in which case use the Tungsten preset.
**Still Life Sequences
***Click to view the high-resolution image.*
|Still Life Scene|
|ISO 80||*ISO 80*|
|*ISO 100*||ISO 100|
|ISO 200||ISO 200|
|*ISO 400*||*ISO 400*|
|*ISO 800*||*ISO 800*|
|*ISO 1600*||*ISO 1600*|
*Low Light – 30 lux
*We also record footage in low light, at 30 lux. In this light, the A720 IS still has some color error, but much less than in bright light. Noise is visible in low light, but a lot lower than some competing cameras.
We take footage of the resolution test chart to determine the sharpness of video clips. Note that video is recorded in Standard Definition (640 x 480 pixels), and will always have far less resolution than a still picture taken with the same camera. In Movie mode, the A720 IS resolves 321 lw/ph horizontally with 7.2 percent undersharpening, and 389 lw/ph vertically with 8.4 percent oversharpening. These are decent numbers for a camera in Movie mode.
We record footage of moving cars and pedestrians on the street to see how cameras handle motion in videos. The video shows very good detail, but tends to be slightly overexposed and has abundant moiré. Motion is pretty smooth, but moving objects get a little jerky when moving off the frame. Overall, the A720’s Movie mode is solid for a digital camera, though certainly not the best we’ve seen this year.
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