Canon PowerShot G3The third generation of Canon's popular G model retains last year's 4 megapixel CCD, but brings a 4X zoom lens and a host of other improvements.<<Optics :(Previous) | (Next): Shutter Lag & Cycle Time Tests>> Page 6:Exposure & FlashReview First Posted: 9/16/2002 |
Exposure
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The G3 offers excellent exposure control, with Automatic (AUTO), Program AE (P), Shutter Speed Priority (Tv), Aperture Priority (Av), and Manual (M) exposure modes, as well as a handful of special settings for specific shooting situations. Under the Automatic exposure mode, the camera controls both shutter speed and aperture settings, giving you control of digital telephoto, flash, compression, and image resolution. The Program AE mode also takes control of the shutter speed and aperture settings, but allows you to adjust all other exposure controls, including ISO, Exposure Compensation, Flash, Flash Exposure Compensation, Light Metering, AE lock, Auto Exposure Bracketing, White Balance, Contrast, Sharpness, and Color Saturation.
Shutter Priority mode puts you in control of the shutter speed setting (from 1/2,000 to 15 seconds), while the camera chooses a corresponding lens aperture. As with the Program AE mode, you maintain control over all other exposure options. Aperture Priority works along similar lines, except that you control the aperture (f/2 to f/8) and the camera chooses the best shutter speed. Both the shutter speed and aperture values are displayed on the LCD monitor. If the camera doesn't agree with the exposure settings you've selected, the LCD indicators will turn red (when you half press the Shutter button), letting you know that either the aperture or shutter speed needs to be corrected.
The shutter speed range on the G3 is expanded over that of the G2, at the high side of its range. While the G2 had a maximum shutter speed of 1/1,000 that was only available when an aperture of f/8 was selected. Maximum speed with apertures from f/3.5-5.0 (wide to tele) was 1/800, and only 1/640 with the lens wide open. By comparison, the G3 can shoot at 1/1,250 with the lens wide open, and can go all the way to 1/2,000 with aperture settings of f/4.0 or smaller. (In manual exposure mode, the shutter speed and aperture settings interlock such that you can only select valid shutter speed/aperture combinations. That is, if the aperture is wider than f/4, you won't be able to select the highest shutter speeds. Likewise, if you begin with a smaller aperture and have the shutter speed set higher than 1/1250, you won't be able to set the aperture to f/4 or wider without first reducing the shutter speed.)
Several preset exposure modes are also available for shooting under special conditions. Portrait mode uses a large aperture setting to reduce the depth of field, resulting in blurred backgrounds and strong focal emphasis on the primary subject. Landscape mode uses a small aperture to keep both the foreground and background in sharp focus. A slow shutter speed is also common in Landscape mode, so it's recommended that you use a tripod.
Night Scene mode uses a slow shutter speed to capture the color and detail of an evening setting, along with a flash exposure to illuminate the primary subject in the foreground. When slow shutter speed and flash are used together, the overall scene is more evenly exposed. This mode can also be combined with the Red-Eye Reduction flash for portraits. A tripod is also recommended when working in Night Scene mode, and portrait subjects should be warned to remain still after the flash, until the shutter is closed.
Stitch-Assist mode helps you align successive shots for later assembly into a panoramic image, using software Canon includes with the camera. (See the section on Stitch Assist below for more information on this mode.)
A quick-review mode allows you to confirm the recorded image immediately after exposure. To access the Review mode, you can simply continue to hold down the Shutter button after the exposure. - The just-captured image will remain displayed on the LCD until you release the shutter button. (I really like the convenience of this feature, as it's easy to access when you want it, without tying you down with long review times when you don't need them.) Or, you can turn on the Review function through the Record menu, which displays the image for anywhere from 2 to 10 seconds, in 1-second increments. You can immediately erase the image by pressing the "*" button, which pulls up a small erase menu on the bottom of the monitor. Press the Right arrow button to highlight "OK" and press the Set button to complete the erasure.
An interesting wrinkle added to the G3's feature set is the ability to decide after you've shot a photo whether you want to save it to JPEG or RAW file format. If the camera is set to record normally in JPEG format, you can elect to save the just-captured image to a RAW file by pressing the FUNC button at any time during the image-review period. (Whether you're reviewing the image by continuing to hold down the shutter button, or via a preset review period programmed through the setup menu.) This seems like a handy option, as you could elect to save any images with problematic exposure as RAW files to maximize the data you'll have to work with on the computer after the fact.
Exposure compensation can be adjusted from –2 to +2 exposure values (EV) in one-third-step increments. The camera's metering system offers three operating modes: Evaluative (a new addition on the G3), Center-Weighted Averaging, and Spot Metering. Evaluative metering looks at a number of points throughout the frame, and evaluates the brightness range and distribution between them to come up with the best exposure setting. Center-weighted averaging is based on an averaged reading of the overall scene, plus a reading from the center of the viewfinder or LCD monitor. Spot metering reads only the center of the image - that area that falls within the crosshairs of the viewfinder or within the small square that pops up on the LCD monitor when you press the Spot Meter button. Spot metering is useful when you're shooting under backlit conditions. In these situations, you can use the spot meter to obtain a reading of the area you want properly exposed, then lock the exposure with the AE Lock function, (activated by pressing the "*" button on the back panel in record mode), and recompose your shot for the final exposure. (Note: depressing any other button on the camera will disengage the Spot Metering function.)
Through
the Record menu (Spot AE Point submenu), you can also link the Spot Metering
area to the FlexiZone AF point described earlier, through an option on the record-mode
setup menu. When the Spot AE Point option of "AF Point" is selected,
and the spot metering option is activated, the AF box acquires a set
of inner brackets indicating that spot metering is active, and that the AF box
is where the metering is being done. If the Spot AE Point is set to "Center",
the white brackets will appear in the center of the LCD screen, indicating that
this is where the Spot AE metering is being done, regardless of the position
of the AF point.
The
G3 offers nine White Balance modes, including Auto, Daylight, Cloudy, Tungsten,
Fluorescent, Fluorescent H (for daylight-balanced fluorescents), Flash, and
two separate Custom modes. The Custom mode lets you manually set the white balance
by holding a white card in front of the camera and pressing the "*"
button to set the value. The G2 had a single Custom white balance setting, and
I like the addition of a second one to the G3. Having a second Custom setting
would make it easy to move back and forth between scenes with radically different
lighting. - An example might be a shooting assignment that had you moving between
indoor and outdoor spaces at night, with different types of artificial lighting
used in the two settings. You could set one Custom white balance for the indoor
shots, and the second for the outdoor ones.
ISO film speed equivalents are set in a submenu of the FUNC button, with choices of Auto, 50, 100, 200, or 400 ISO values. The higher the ISO setting, the more you can extend the camera's exposure range in low-light situations. Just keep in mind that higher ISO values have slightly lower quality levels and increased image noise. Other manual exposure adjustments in the Record menu include Sharpness, Contrast, and Saturation controls.
Flash
The
G3's built-in flash operates in any one of a total of nine modes: You can leave
it turned off, have it fire all the time, or only fire automatically, as the
camera sees fit. In any of its active modes, you can turn on red-eye reduction
(which illuminates the bright AF assist light on the front of the camera before
the flash fires, to make your subjects' pupils contract), or enable Slow Sync
mode, which combines the flash with a slower shutter speed to allow more light
from the scene lighting to enter the lens. The combination of off plus two active
modes (forced or auto) with four variations each (normal, red-eye w/o slow sync,
red-eye w/slow sync, and slow sync w/o red-eye) adds up to 9 modes total, although
Canon only counts five modes in their manual for the G3. The main flash modes
of off, forced on, and auto are selected via the Flash/Index button in the upper
left-hand corner of the G3's rear panel. Slow Sync and Red-Eye Reduction modes
are controlled via the record-mode setup menu.
The amount of flash power can be adjusted from -2 to +2 EV in one-third-step increments by the using the FUNC button on the camera's back panel together with the Omni Controller to access the Flash Exposure Compensation adjustment menu. You can also lock the Flash Exposure Setting (FE Lock) for a specific area of your subject, just as you would with a normal exposure. Simply center the portion of the subject you want to have metered and press the "*" button to lock the flash exposure. The flash will fire a pre-flash to lock the exposure reading, then you can recompose your image and make the exposure with the FE Lock in place. (Note that pressing any other button after the "*" button will cancel the flash exposure lock.) Canon rates the G3's flash effectiveness from 2.3 to 14.8 feet (70cm to 4.5m). (I'll verify this once I receive a production model to test.)
In
addition to its built-in flash, the G3 features a hot shoe for mounting more
powerful external flash units. Canon recommends using its own Speedlight 220EX,
380EX, 420EX, or 550EX models, but other manufacturers' models should work as
well. The G3's flash sync speed appears to be similar to that of the G2, although
the draft manual I received with my prototype test unit didn't include any specs
for sync speed. Experimenting on my own though, I found that whenever the internal
flash fired, shutter speed was limited to a maximum of 1/250. (I suspect that
the maximum sync speed with an external, third-party flash is 1/125, as was
the case with the G2.)
Canon's handling of the sync-speed limitation on the G3 bothers me a little though. If you're in auto or programmed exposure mode, all is well, the camera simply won't select a shutter speed greater than 1/250 when the flash is enabled. In Tv (shutter speed priority) or Manual mode though, you can select shutter speeds as fast as you want (all the way up to 1/2000), but if you have the flash turned on (forced flash is the only mode available, the Auto option is only offered in Programmed exposure mode), the actual shutter speed will be restricted to 1/250! I disagree with this design choice: When a camera is in a mode that gives the user control over some parameter or other (such as shutter speed), the camera shouldn't arbitrarily override the user's settings. While the G3 does show you that the shutter speed has changed to 1/250 when you half-press the shutter button, it's easy to miss seeing the changed shutter speed unless you're on the lookout for it. I guess it's good that the camera tries its best to deliver you a well-exposed shot, but I'd really like to see some way of optionally preventing an override like this.
Carried over from the G2 is automatic Speedlight EX recognition in Aperture-Priority mode. When the camera senses that a Canon EX-model external flash is mounted and in ready mode, it automatically sets the shutter speed to 1/60 second. Note though, that the G3 must be in full manual mode to use with other brands of flash units. (Since the Aperture Priority mode will normally select a very slow shutter speed when an "unrecognized" flash unit is attached.)
The G3's compatibility with Canon's various external flash units has been enhanced relative to that of the G2. The G2 was the first prosumer digicam of Canon's that supported their Macro Ring Lite, model number MR-14EX. Ring lights are great for evenly illuminating close-in macro subjects, and the availability of one for the G2 and G3 is a decided plus for many potential industrial and medical applications. The G3 goes one step beyond the ring light compatibility though, adding support for Canon's very sophisticated Macro Twin Light unit (model MT-24EX), which has two independent flash heads, with exposure-ratio control between them.
Beyond the excellent strobe support for macro shooting, the big news with the G3's external flash capabilities is that it supports the full range of wireless operation of Canon's high-end speedlights, via the Speedlight Transmitter, ST-E2. This makes the G3 an exceptionally versatile platform for digital strobe photography.
Auto Exposure Bracketing
The Auto Exposure Bracketing (AEB) mode is another function controlled by the FUNC button's sub-menus. It automatically captures a series of three images, each at a different exposure setting. You can manually set the exposure step size in one-third-step increments, covering a range from -2 to +2 EV, by depressing the FUNC button, scrolling to the AEB option with the Omni Controller, and then using the Omni Controller again to choose the amount of variation between exposures. Depress the Set button, then fully depress the Shutter button to start the series. The camera makes all three exposures with just one press of the Shutter button. This function cannot be used with flash photography. If the flash fires, only one image will be recorded.
Continuous Shooting
Controlled by the Continuous / Self-Timer / Wireless Remote button on top of the camera, the G3's Continuous Shooting mode captures multiple consecutive pictures at up to 1.5 frames per second (fps). (Canon rates this option's speed at 1.5 frames/second, matching the results from my own lab tests of the camera.) This frame-capture rate may vary slightly, depending on image quality, functions in use, and the amount of internal memory available. (1.5 fps is based on a "Large" image quality setting, "SuperFine" JPEG compression, and the LCD monitor and flash turned off. Oddly, this rate decreases slightly to 1.46 frames/second for "Small/Basic" settings.) The G3 will continue to capture images as long as the Shutter button is depressed, or until the camera's internal memory fills up. I again noticed one slightly odd behavior with the G3's continuous shooting mode that I also saw with the G2 (and indeed, with a number of digicams as well): The interval between the first and second shot of the series is always about 0.1 - 0.15 seconds longer than subsequent ones, regardless of the size or quality setting being used. (If having a relatively consistent interval between each shot of a continuous-mode series is important to you, start slightly early, and discard the first frame.)
Through the Record menu, you can also select a High Speed Continuous Shooting mode. In this mode, the capture rate is much faster than normal Continuous Shooting (approximately 2.3 fps in our measurements, rated at 2.5 fps by Canon).
We first saw these two continuous shooting modes with the G2, and at that time, I was puzzled as to what the difference between the two Continuous Shooting modes might be. When I asked Canon what the difference was, I learned that it has to do with how the camera manages its buffer memory and CPU activity. Both continuous modes capture data directly to the buffer memory, but the "standard" continuous mode does some amount of the signal processing on the fly. The result is that cycle times in normal mode are slower, but the camera can record longer bursts before having to pause to empty its buffer. High Speed continuous mode captures more quickly, but doesn't do the processing on the fly, with the result that fewer shots can fit in the buffer memory before having to empty it.
Movie Mode
The G3 also offers a Movie mode, which is accessed by turning the Mode dial on top of the camera to the miniature movie camera symbol (a camera will appear in the upper left corner of the LCD display). The AVI / Motion JPEG files are recorded at either 320 x 240 or 160 x 120 pixels, at approximately 15 frames per second. Recordings can last as long as three minutes at either resolution setting, depending on the amount of memory available on the CompactFlash card. (Thanks to Canon's new "Digic" high speed image-processing CPU, the three minute recording length is a significant upgrade from the G2, which had a maximum record time in 320x240 mode of only 30 seconds, and two minutes in 160x120 mode.) To begin recording, you simply press the Shutter button once. A red dot icon appears in the upper right-hand corner of the LCD screen, indicating that recording is in progress, and a counter in the lower right-hand corner begins counting up to show the length of the current clip in seconds. To stop recording, simply press the shutter button again. (Note that the recording options are largely preset in Movie mode: Macro mode, Resolution, Exposure Compensation, White Balance, Manual Focus, Picture Effects (vivid, sepia, etc), self-timer, wireless delay, and AF assist beam are the only adjustable functions.)
When finished, you can view the recording by toggling the power switch to the playback position. Pressing the Set button brings up a little VCR-style playback control panel, with buttons for play, fast forward and fast reverse, go to end and go to beginning. A scissors icon lets you trim the movie to select just the part you're most interested in, and save it to the memory card as a separate file. When the movie is playing back, the control panel disappears, but you can stop playback by hitting the Set button again. In movie playback mode, the up/down positions of the Omni Controller adjust the audio volume.
Stitch-Assist Mode
The Stitch-Assist mode records a series of overlapping images that can be stitched together to create horizontal or vertical panoramas or stacked, 2 x 2-frame rectangular composites. A framing guideline for each format appears in the LCD monitor to help line up successive shots. For the horizontal and vertical panoramas, you can take as many images in a series as you want, enabling you to record a full 360-degree circle of the surrounding scenery. The 2 x 2 mode uses a series of only four images, starting from the top left corner and moving in a clockwise direction, to create a complete composite. Once the images are downloaded, you can use Canon's PhotoStitch program to seamlessly combine the images in your computer.
Self-Timer Mode
The Self-Timer button on top of the camera also controls the Continuous Shooting and Remote operating modes. When set to the Self-Timer / Wireless mode, the camera displays the standard self-timer icon (a clock counting down) in the LCD display, and the self-timer icon with a remote (radar) symbol in the LED panel on top of the camera. When in Self-Timer mode, depressing the Shutter button activates a 12-second countdown, during which the bright white AF-assist lamp on the camera's front panel blinks, gaining speed in the last two seconds. If the camera's Beep function is turned on in the Setup menu, you will also hear the beep counting down. While in Self-Timer mode, you can also trigger a two-second countdown by pressing the Shutter button on the remote control.
Interval Shooting
New on the G3 is a built-in intervalometer, that lets you program the camera for extended time-lapse exposure sequences. You can choose intervals between successive photos of 1 to 60 minutes, and anywhere from 2 to 100 photos in the series. This opens lots of opportunities for interesting time-lapse shots, but be sure to use the AC adapter for any long sequences, to avoid any interruption of power.
Remote Sensor/Transmitter
The G3's Wireless Remote Control allows you to trigger the camera from as far away as 16.4 feet (5 meters) in front of the camera. While the G2 had a fixed two second delay between pressing the IR remote trigger and the shutter actually firing, the G3 lets you set the delay to zero (big kudos for that!), two, or ten seconds. Besides simply triggering the shutter, you can also use the IR remote to adjust the optical zoom lens with its two Zoom buttons, and activate the LCD monitor with its Display button. By rotating the LCD monitor so that it faces you (or the subject), you can use the Zoom buttons to compose the image and the Display button to scroll through the G2's LCD information screen to check exposure settings. In Replay mode, the remote control can be used to scroll through stored images, scroll around areas within a magnified image, view an index of up to nine captures, and replay movies.
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