I was recently looking for a small, pocketable digicam to serve as a backup for my DSLR system. I wanted something with full manual control of shutter speed and aperture (and manual focus if possible), something capable of shooting in low light (which means an image stabilized lens and high ISO capability), a decent zoom range, good image quality and a reasonable price.
As I described in another article, I decided to go with a Canon Powershot A720is based on the specs as listed below:
The A720IS also has a set of movie modes. It can record VGA (480x640 resolution) video at 30 frames/sec for either 1hr or when the file reached 4GB, whichever comes first. In the highest image quality mode, 4GB gives you just over 30 minutes of recording. With higher compression you can get about 1hr of VGA video. The A720IS is also capable of recording at 240x320 resolution at 30 frames/sec or at 160x120 resolution and 15 frames/sec (for emailing). The time limit for 160x120 recording is 3 minutes. Sound (mono) is also recorded while shooting movies.
Image stabilization operates in movie mode, making handheld shots much smoother, however you can't optically zoom the lens while recording.
ISO can be set to 80, 100, 200, 400, 800 and 1600. Above ISO 400 noise becomes pretty noticeable and at ISO 1600 the automatically used noise reduction algorithm reduces image detail significantly as you can see in the set of 100% crops above. I've seen other reviews which imply that ISO 1600 is so bad as to be useless, but I think that's too harsh a judgment. I'll admit that if you look at an ISO 1600 shot on a monitor at 100% it looks pretty bad - but that's just about the equivalent to looking at a 24" x 36" print from a distance of 1ft. I took a number of shots at ISO 1600 and made 4x6" prints from them. To me they looked pretty good, in fact probably better than prints I remember having made from ISO 1600 film some years ago. So although ISO 1600 images are noisy and details are soft when compared to shots at ISO 80, they are far from useless as long as you stick to small prints. The images below are 25% crops from the original image. On a typical monitor (17" 1280x1024 resolution) they will represent section from a prints that is maybe 5"x7"
I wouldn't shoot at ISO 1600 unless I absolutely had to, but at least it's there if you really need it.
There's very little sign of vignetting and sharpness is consistent from center to corner. On the right are 100% crops from the image center and the extreme bottom left corner. There's little or no evidence of "purple fringing" or chromatic aberration at this focal length.
The shot was taken with all parameters (sharpness, contrast, saturation) set to "normal". In common with most digicams the A720is is set to give pretty sharp images with the default settings, which means that the default sharpness setting results in some very slight edge effects when looked at under 100% magnification. Sharpness can be reduced if you prefer to do your sharpening in Photoshop, where you have somewhat greater control over the parameters used. However the default values make excellent looking prints (which is what really counts).
At the widest setting (35mm equiv.), there is some chromatic aberration visible as shown in the image on the left below. This is a 100% crop from an image shot at f2.8 at 35mm (ISO 80)
Chromatic aberration can quite well corrected in post-exposure processing using image editors such as Photoshop. The image on the right above shows the effects of such correction.
An additional advantage of the optical viewfinder is that you can use it even in the brightest sunlight, where it's sometimes tricky to see the LCD image clearly, plus I think you can hold the camera steadier held up against your eye than held out at arms length to view the LCD.
While the Powershot A720is has a shutter speed range of 15s to 1/2000s, not all speeds are available in all modes. While you can set 15s in both M (Manual) and Tv (Shutter Priority) modes, in Av (Aperture Priority) and P (Program) modes the shutter speed won't go longer than 1s. I've seen similar behavior on other Powershot cameras and I don't really know why there is this limit, but just be aware of it). It's not a problem since if you really want a long shutter speed, just switch to Tv or M.
In manual mode the camera displays the set shutter speed and aperture plus an indicator of exposure from -2 (two stops underexposed) to +2 (two stops overexposed) in 1/3 stop steps. When it displays "0", exposure is correct.
The lens aperture is adjustable in 1/3 stop steps. At 35mm the range is f2.8 to f8 and at 210mm the range is f4.6 to f8. You can't stop down past f8 in any mode. This is because the senor is so small that if you could stop down to a smaller aperture, the image would be significantly softened due to diffraction effects. All small sensor digicams are like this, it's the nature of the beast.
Flash exposure can be set to manual or auto when using Tv, Av and M modes. In auto you can dial in from -2 to +2 stops of flash exposure compensation (in 1/3 stop steps). In manual mode there are three power levels, minimum, middle and maximum. With a fixed flash power output you control flash exposure via the aperture and ISO settings you chose. Using a flash meter I measured the maximum flash output GN as 16 (ft, ISO 100). In M, Av, Tv and P modes you can manually set the flash to 2nd curtain sync. In manual mode you just get one flash, so you could use it with a traditional optical slave flash. In auto mode the flash emits a metering pre-flash, so you need a digital aware slave which fires only on the main flash, not on the pre-flash.
In manual focus mode you can add a 10x magnifier to the center of the screen to make it easier to judge focus. A scale is displayed (in ft or m), though it's not very exact. It does show you where you are within the focus range though. There are two scales. One runs from 50cm to infinity with marks at 1, 2, 5m and infinity. If you close focus the scale switches to 0 to 50cm with marks at 10, 20 and 50cm.
Prior to shooting the screen displays the shooting mode, ISO setting, shutter speed, aperture, exposure compensation, focusing mode and image stabilization indictor. The above image shows the camera was in Program mode, set to ISO 1600, image stabilization was active and the camera was in macro focusing mode.
Images are stored as JPEG files at one of three different compression levels. The lower the compression the larger the files, but the higher the image quality. The A720is cannot store images in RAW format (in common with most other current Canon digicams)
The A720is doesn't display a battery level indicator until the voltage drops to the point where it warns you to change the batteries. You do get a little time after the warning, but not all that much, so it would be advisable to carry a spare set of batteries with you.
The only advantage of having the tripod socket close to the left edge of the camera is that it means you can change the batteries and memory card without having to remove the camera from the tripod, since the battery and memory card door is over on the right side.
What's missing? Well, a 28mm lens setting would be nice and the ability to record images in RAW mode would also be useful, but I can live without either one given the price and features of the A720is.
Note that the A570is is essentially the same camera, but with a 35-140mm zoom lens and a 7.1 MP sensor. If you don't need the extra zoom range of the 720is, you can save about $40 by buying the A570is.
|You can get the Canon Powershot A720is from Amazon.com like I did. If you only want a 4x zoom and 7.1MP, you can save $40 or so by buying the A570is, but I think the A720is is a better deal.|
UPDATE AUGUST 2008 - As happens with all cameras, Canon have updated the A720is and A570is to the new A2000is and A1000is respectively. These new cameras seem to have most of the features virtues of their predecessors, plus a higher pixel count and a slightly slimmer shape. You can read a brief preview of the new models HERE. If I was looking for an A720is (which I'm not since I already have one!), I'd now consider the A2000is. It looks very similar to the A720is, though it has lost its optical viewfinder in favor of a larger (3") LCD screen. I'd also take a close look at the new SX110is, which has a longer (10x) lens.