Canon PowerShot A20Canon's "value priced" 2 megapixel camera has 3x zoom, takes great pictures!<<Optics :(Previous) | (Next): Shutter Lag & Cycle Time Tests>> Page 6:Exposure & FlashReview First Posted: 5/10/2001 |
Exposure
The A20 offers a relatively uncomplicated user interface, and a control layout that is very similar to other Canon PowerShot cameras. The numerous external controls decrease reliance on the camera's menu system, though the LCD's information display is automatically activated whenever a control button is pressed. This still saves on battery power, however, because the information display automatically turns itself off after a few seconds, shutting down the LCD monitor in the process (as long as it was previously inactive).
The Mode dial on the camera's back panel controls the operating mode, placing the A20 into Playback mode, or Automatic, Manual, and Stitch Assist Shooting modes. Exposure is automatically controlled at all times, with only limited user controls depending on the Shooting mode. For example, Automatic mode provides control over Flash, Focus, Drive, Resolution, and Compression settings, while Manual mode gives the user control over White Balance and Exposure Compensation, in addition to the settings available in Auto mode. Stitch Assist mode provides all of the available controls except for Auto Flash, Red-Eye Reduction, Digital Zoom, and Continuous Shooting. Basic exposure decisions, such as shutter speed and aperture setting, remain under automatic control in all three Shooting modes.
An Instant Review function displays the captured image on the LCD screen for two or 10 seconds, which is adjustable through the Setup menu. The Instant Review screen gives you the option of deleting an image, without recording it to the CompactFlash card, simply by pressing the Exposure Compensation / White Balance button. This pulls up the Erase screen, with an option to cancel the action. You can also turn the Instant Review function off, which should save on battery usage.
Shutter speeds range from 1/1,500 to one second, and lens apertures from f/2.8 to f/4.8 (depending on the telephoto setting), although neither setting is reported on the LCD information display. To determine exposure, the camera uses an evaluative metering system linked to the focus area, or center of the image. One notable feature of the PowerShot A20 is its automatic noise reduction for exposures longer than 1/6 second. We found this to be quite an effective in our low-light test shots, which showed very low noise levels.
Light sensitivity is rated at an ISO 100 equivalency, and is automatically raised to ISO 150 in low-light situations. This boost wasn't enough to impact our low-light test shots, however, as we were only able to obtain bright, usable images at eight foot-candles or 88 lux (common street lighting at night equates to about one foot-candle, or 11 lux).
The A20's White Balance settings include Auto, Daylight, Cloudy, Tungsten, and Fluorescent options, accommodating most common light sources. Pressing the Exposure Compensation / White Balance button twice displays the White Balance menu, navigable with the right and left arrow buttons under the LCD monitor. A single press of the same button displays the Exposure Compensation adjustment, which allows you to lighten or darken the image from +2 to -2 exposure equivalents (EV) in one-third-step increments. A 10-second self-timer is accessible by pressing the Drive button twice. Once in Self-Timer mode, a half-press of the Shutter button locks focus and exposure, while a full press triggers the countdown. The Self-Timer lamp (an orange light emitted by the flash) blinks every second for the first 8 seconds of the countdown and blinks more rapidly for the last two seconds. A timer also beeps audibly in sequence with the orange light.
FlashThe A20's built-in flash has a working range of 2.5 to 13.8 feet (0.76 to 4.2 meters) at the wide-angle setting, and from 2.5 to 8.2 feet (26 to 76 cm) at telephoto. In Macro mode, Canon reports that the flash is effective for the telephoto shooting range, which is 10.2 inches to 2.5 feet (26 to 76 cm), but that the flash may be too bright for the closer shots allowed by the wide-angle lens setting, 10.2 inches to 2.5 feet (26 to 76 cm). In our testing, however, we found the flash very effective at the wide-angle Macro setting.
The flash has five operating modes, controlled by the Flash button on the camera's back panel: Auto, Red-Eye Reduction, On, Off, and Slow Synchro. The Automatic flash fires the flash in low-light situations or when a subject is backlit. Red-Eye Reduction mode works in the same manner, although it fires a small pre-flash before the full flash to reduce the occurrence of red-eye effect (a red reflection from the flash in the subject's pupils). The On and Off flash modes are self-explanatory. Slow Synchro mode works with a slower shutter speeds (usually one-second), which allows more ambient light into an image.
In our testing, we found the A20's flash brightest at 8 feet from the target, with decreased (though still fairly bright intensity) as far as 10 feet. Flash intensity continued to decrease in brightness from 11 to 15 feet, though the flash was weakly effective at the 15-foot distance.
The A20's flash also serves as an autofocus (AF) Assist light and Self-Timer lamp, emitting a soft, orange light from the flash window. When used as an AF Assist light, the orange light shines on the central portion of the subject, helping the camera determine focus in low-light situations. In Self-Timer mode, the orange light blinks during the 10-second countdown until the shutter is released.
Stitch-Assist Mode (Panorama)
The A20 features Canon's popular Stitch-Assist mode, which allows you to create panoramic images by shooting a series of images and then "stitching" them together on a computer. As many as 26 consecutive images can make up a panoramic series, all captured using framing guidelines provided on the LCD monitor (to help line up each shot correctly). A shot confirmation after each image allows you to reshoot an image if necessary. Auto and Red-Eye Reduction flash modes, as well as the Digital Zoom, are not available in Stitch-Assist mode. Canon also notes that a television cannot be used as a viewfinder when shooting in Stitch-Assist mode. PhotoStitch software is included on the software CD accompanying the camera.
Continuous Shooting Mode
Accessed via the Drive / Self-Timer button on the camera's back panel, the Continuous Shooting mode allows you to capture a series of images at approximately 2.5 frames per second. The camera snaps images continuously for as long as the Shutter button is held down, or until the CompactFlash card is full. Images are immediately recorded to the camera's buffer memory. Once the buffer memory is full, images are recorded to the CompactFlash card. The series will resume if you continue to hold down the Shutter button, but only after the buffer has been cleared. Shot-to-shot cycle times vary depending on the image size and quality settings, whether or not the LCD monitor is enabled, and the amount of image information to be recorded. The flash is available in this mode, but decreases the shot-to-shot cycle time to allow the flash time to recharge. Continuous Shooting is available in Manual mode only.
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