Canon PowerShot A720 IS Digital Camera Review

by Karen M. Cheung
Published on October 17, 2007

Navigation
Intro	Testing/Performance
Components	Design / Layout
Modes	Control Options
Image Parameters	Connectivity / Extras
Overall Impressions	Conclusion
Sample Photos	Photo Gallery
Specs / Ratings

Color (11.26)
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.

Click to view the high-resolution image

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.

Auto (12.76)
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.

Auto WB - Shade Illumination

Auto WB - Flash Illumination

Auto WB - Fluorescent Illumination

Auto WB - Tungsten Illumination

Preset (13.99)
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.

Shade WB - Shade Illumination

Fluorescent WB - Fluorescent Illumination

Tungsten WB - Tungsten Illumination

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 (7.76)
Not all photos are taken in bright light, which is why we also test cameras in less-than-ideal shooting situations. To see how cameras perform in low light, we photograph the ColorChecker chart at light levels of 60, 30, 15, and 5 lux. Sixty lux corresponds roughly to a softly lit living room, 30 lux is a room illuminated by a 40-watt bulb, 15 lux is about as bright at a room lit solely by a television, and 5 lux is very low light that tests the limits of camera sensors. All photos are taken at ISO 1600.

Low Light Tests
60 Lux	30 Lux
15 Lux	5 Lux

The A720 IS is able to expose properly at all of our low light levels, which we expect for a camera with as many manual controls. Color accuracy stays very good in low light down to 15 lux, though noise levels are through the roof. The noise is so bad at ISO 1600 that it is apparent even in downsized versions of the photos. The camera has good low light capability, but the only time to use ISO 800 or 1600 is if all your photos are coming out blurry.

We also test long exposure performance in low light, this time at ISO 400. In exposures longer than one second, color accuracy suffers significantly, but noise levels are much lower than at ISO 1600. Colors are oversaturated by as much as 10 percent, which isn’t necessarily a bad thing if you’re shooting a sunset, for example. Noise levels stay even from 1 to 15 second exposures, showing no obvious signs of extensive noise reduction. One thing to note is that the A720 IS (like most Canon point-and-shoots) cannot manually white balance properly for long exposures. To manually white balance in these situations, you must first increase the shutter speed to at least a half second or faster, set your white balance, and finally set the shutter speed back to a long exposure and take your photo.

Dynamic Range (4.88)
Dynamic range is an image quality factor that describes the range of tones a camera can discern. A camera with good dynamic range will be able to maintain detail in both bright and dark areas in a single photograph. This is especially relevant when shooting outside in bright sunlight (bright highlights and dark shadows), or snapping photos at a wedding (white dress and black tux). We test dynamic range by photographing a backlit Stouffer test chart at every ISO sensitivity. The Stouffer chart consists of a long row of rectangles, each a slightly darker shade of gray than the next, arranged from brightest white to darkest black. The more rectangles the camera can distinguish, the better its dynamic range.

The A720 IS has good dynamic range at ISO 80, but falls off quickly at higher ISO speeds. This is mostly due to the high noise levels at higher ISO speeds, which drown out image detail, especially in dark areas of photos. Like we mentioned in the noise section above, keep this camera at as low an ISO speed as possible in order to keep your photos looking their absolute best.

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.

Startup to First Shot (8.1)
The A720 IS takes 1.9 seconds to turn on and snap its first shot.

Shot-to-Shot (9.1)
In Continuous shooting mode the camera takes photos roughly every 0.9 seconds until the card is filled.

Shutter-Shot (9.0)
The A720 IS has no measurable lag time when the shutter is held halfway down and prefocused, but takes 0.45 seconds to snap a picture when it hasn’t been prefocused.

Processing (7.0)
The camera takes 1.5 seconds to process a full resolution superfine 4.5 MB photo taken at ISO 125.

Video Performance (4.54)
Bright Light – 3000 lux
We test video performance by recording footage of our color charts under bright, even studio light set to 3000 lux with the camera set to Auto white balance. Under these tungsten lights, the A720 IS has extreme color error and oversaturation, which is actually normal for a camera shooting under tungsten lights and set to Auto white balance. Noise levels are very low in such bright light.


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.


Resolution
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.


Motion
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.