Canon PowerShot A570 IS

Manual Control Options
The PowerShot A570IS offers a surprising range of manual control for such a simple camera. The user can manually set aperture and shutter speed, ISO, white balance, and focus.

Focus
Auto Focus (8.0)
The PowerShot A570IS analyzes data from the imaging chip to set the autofocus. That's typical of compact cameras, and it is one of the differences between them and DSLR cameras, which have independent focus sensors. The DSLR system works faster, but it is more expensive, and usually covers a smaller portion of the frame. The A570IS can focus on 9 rectangular areas toward the middle of the frame. When set to display the preview on its LCD, the A570IS shows green around the rectangles where it focuses. In AiAF mode, the A570IS chooses which of the 9 areas are most important. With AiAF off, only the center rectangle is active. In Face Detection mode, the A570IS identifies faces in the frame, and focuses on them.

The A570IS focused well in low light, getting sharp shots even when it had to underexpose them. It is also accurate in more typical lighting. The focus mechanism isn't fast enough for squirming puppies or other moving subjects. Compact cameras have a hard time with that, and the A570IS rates about average, but compact camera users shouldn't expect fast focusing from inexpensive, small cameras.

The face detection option in the PowerShot A570IS's AiAF autofocus mode works as it should; it finds the human face – or multiple faces – in a scene, and focuses on them. It works with real people, photographs of people, and even somewhat expressionistic paintings of faces. It does not, however, work on animals. When the system recognizes a face, it shows a rectangle around it on the LCD and tracks it as the face moves around the screen. It works for both horizontal and vertical photos. Oddly, when we rotated the camera to about 45 degrees after it had latched onto a face, the camera wasn’t able to track it.

Manual Focus (3.5)
The PowerShot A570IS offers a workable manual focus system. In manual focus mode, the center of the frame is enlarged, and the 4-way controller racks focus near to far. A distance scale appears on screen. The distance scale isn't much use, but the magnified area is pretty easy to read. Manual focus is slow, but the mechanism stops immediately when the user stops pressing the controller. That's a big advance over other manual systems, where the camera over- or under-shoots the focus point.

Generally, the auto focus system works better than the manual system, but in the rare case where a crowed scene flummoxes the AF, manual might be the way to go. The PowerShot A570IS’s auto focus can be activated when in the manual focus mode with a tap of the shutter release.

Exposure (7.75)
The user can set exposure compensation 2 EV above or below the metered reading in 1/3-EV steps on the PowerShot A570IS. The option is available in most scene modes as well as aperture and shutter priority and the program modes. Flash compensation is available only in manual, aperture and shutter priority and program. The A570IS doesn't offer bracketing.

When engaged, the A570IS's face detection system will also set the exposure for dected faces, helping ensure the people in the frame are visible and properly exposed.  

Metering (7.0)
The PowerShot A570IS has the three standard metering patterns: evaluative, spot and center-weighted. The automatic modes use the evaluative system, which reads several locations across the frame. The spot mode reads a small area at the center of the frame, and is useful for manual exposure. Center-weighted takes a single reading of the whole frame, but concentrates its sensitivity in the middle, which is useful for landscapes.

The PowerShot A570IS's meter produced well-exposed images in good lighting, but the evaluative system is not smart enough to handle backlighting or other high-contract scenes well. It compromised too much, leaving the subject too dark and the background a little too detailed – it should have overexposed the background to allow a better exposure of the subject. To get better results, the user must use the spot meter in one of the manual modes.

White Balance (7.75)
The PowerShot A570IS has automatic white balance, presets for sun, cloudy, tungsten, two kinds of fluorescent tubes, and underwater scenes. It also allows the user to take manual readings. The auto system worked well for snapshots, and the presets delivered pleasing color in casual shooting. Several low-end cameras offer white-balance fine-tuning, allowing the user to tweak color manually. The A570IS lacks that feature, and advanced options such as direct Kelvin settings and white balance bracketing. A simple camera shouldn't be expected to have complicated features, but there would be situations where an A570IS user would benefit from the option to fine-tune white balance.

ISO (7.75)
ISO is the camera sensor's sensitivity to light. It's variable, because the camera can amplify the sensor's signal. The PowerShot A570IS's ISO settings are 80, 100, 200, 400, 800 and 1600. It used to be rare to see compact cameras with settings of 800 and 1600, but they have become common. The high settings produce lower-quality images, but they allow photography in dark situations.

The PowerShot A570IS has two auto ISO settings. One biases lower, for better quality, and the other goes higher, for faster shutter speeds. Both are available in auto modes, plus Program and the aperture and shutter priority modes. In the non-auto modes, the user can set ISO manually. More sophisticated cameras allow the user to set ISO in finer increments, such as 160, 250 or 500, rather than just the full jumps. That's a useful feature, but one that users typically give up with a simple camera like the A570IS.

Shutter Speed (7.0)
The shutter speed is set with the 4-way controller, which is clumsy, but typical for this camera class. The PowerShot A570IS allows exposure times from 1/2000 to 15 seconds. In many of the scene modes, the full range is not available, but in the manual modes the range is available in 1/3-EV steps. The A570IS has a noise reduction system that kicks in for exposures of 1.3 seconds or longer. The range is completely sufficient for typical A570IS users.

Aperture (5.0)
The maximum aperture on the PowerShot A570IS ranges from a fast f/2.8 to a slow, dark f/5.5. With focal lengths from 5.8 to 23.2 mm, the smallest useful aperture is f/8 or 9. The slow aperture at telephoto settings may be the biggest photographic limitation the A570IS user faces. F/5.5 is too small for low-light photography, and too small for really shallow depth of field for portraits – the backgrounds won't be as blurry as the Portrait scene mode description suggests. The 4-way controller isn't an ideal aperture control, but it works. In manual modes, the aperture can be set in 1/3 EV steps.