Canon PowerShot G5The next generation of Canon's popular "G" model updates the line with a larger, 5.0-megapixel CCD.<<Optics :(Previous) | (Next): Shutter Lag & Cycle Time Tests>> Page 6:Exposure & FlashReview First Posted: 08/18/2003 |
Exposure
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The G5 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.
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Shutter Priority mode puts you in control of the shutter speed setting (with a range 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/2.0-3.0 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 numerals indicating the amount of under- or overexposure on the LCD will turn red when you half press the Shutter button, letting you know that either the aperture or shutter speed needs to be corrected. In both Aperture and Shutter Priority modes, you can quickly adjust the designated exposure variable by simply turning the dial. In Manual mode, the dial adjusts both settings, you just press down to alternate between aperture and shutter speed.
Several preset exposure modes are also available for shooting under special conditions. Portrait mode uses a large lens 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, or you can cancel the flash altogether. 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.
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 two to 10 seconds, in one-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.
Just as on the G3, the G5 offers 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, 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, the 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. 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 G5 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. Having two Custom settings makes 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, but keep in mind that image noise increases in more or less direct proportion to the ISO value. Other manual exposure adjustments in the Record menu include Sharpness, Contrast, and Saturation controls.
Flash
The G5's built-in flash operates
in any one of nine available 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 nine modes total. 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 G5's rear panel. Slow Sync and Red-Eye Reduction modes
are controlled via the Record menu. Through the same menu, you can also specify
whether the flash syncs with the first or second curtain. (That is, on shots
with slower exposure times, the flash can fire either as the shutter opens,
or as it's closing.)
The flash exposure 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 Four-Way Arrow pad 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 single pulse 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 G5's flash effectiveness from 2.3 to 16.5 feet (70 centimeters to 5 meters), a figure that agreed with my own test results. (This is a more powerful flash than found on most consumer-level digicams.)
In addition to its built-in flash, the G5 features a hot shoe for mounting more powerful external flash units. Canon recommends using its own Speedlight 220EX, 380EX, 420EX, 550EX, MT-24EX Macro Twin Light, or MR-14EX Macro Ring models, but other manufacturers' models should work as well. The G5's flash sync speed is a maximum of 1/250.
Canon's handling of the sync-speed limitation on the G5 bothers me a little though, as it did on the G3 before it. If you're in Auto or Program AE 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 1/2,000), 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 G5 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 and the G3 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, overriding the normal tendency of Aperture-Priority metering to set the shutter speed based on available lighting. This is very handy, as you can attach an EX-model flash unit, set the camera to Aperture-Priority metering, and then just turn the flash on or off as you wish, without worrying about what the shutter speed is doing. Note though, that the G5 must be in full manual mode to use with other non-Canon flash units. (Since the Aperture Priority mode will normally select a very slow shutter speed when an "unrecognized" flash unit is attached and the scene is dimly lit.)
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 Four-Way Arrow pad, and then using the Main dial to choose the amount of variation between exposures. Depress the Set button to make your selection, then fully depress the Shutter button to start the series. The camera makes all three exposures with just one press of the Shutter button. In AEB mode, the exposures are chosen to bracket whatever exposure setting you've dialed in using the Exposure Compensation adjustment. Thus, the bracketing always occurs around whatever exposure you've chosen based on your evaluation of the scene and the camera's metering.
Note that Auto Exposure Bracketing 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 G5's Continuous Shooting mode captures multiple consecutive images at up to 1.5 frames per second (fps). This frame-capture rate may vary slightly, depending on image quality, and functions in use. (In my own testing, the G5 consistently delivered 1.39 frames/second, in a variety of modes.) The G5 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 G5's continuous shooting mode that I also saw with the G2 and G3 models (and indeed, with a number of digicams as well). The interval between the first and second shot of the series is always about 0.26 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, rated at two frames/second by Canon, and delivering 1.98 frames/second in my tests.
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 sometimes record longer bursts before having to pause to empty its buffer, particularly when working with smaller image sizes and lower quality settings. 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.
The G5 has a fairly generous buffer memory, able to capture between 7 and 9 full-resolution, maximum-quality JPEG files or 3 RAW-format files before slowing. (In continuous mode, it can only capture 2 RAW-format files before pausing.)
Movie Mode
The G5 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. 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, 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.
Quicktime(tm) 3.0 is required to view the AVI/Motion JPEG files recorded by the G5 in Movie mode. Quicktime is included with current versions of the Mac OS (any version later than 8.5), and a QuickTime player for the Windows platform is included on the Solutions Disk bundled with the camera.
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. After each shot, a portion of the image remains on-screen, as an aid to lining up the next image in the series. For the horizontal and vertical panoramas, you can take up to 26 images in a series, enabling you to record a full 360-degree circle of the surrounding scenery. For horizontal or vertical panoramas, you can set the camera to record the series of images either right to left or left to right, top to bottom, or bottom to top. 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 them 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 face with one hand) in the LCD display, and the self-timer icon with a remote symbol (hard to describe, but it makes me think of a radar gun) in the LED panel on top of the camera. When in Self-Timer mode, depressing the Shutter button activates either a 2- or 12-second countdown, as selected via the Record menu. During the countdown time, 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, the camera will also beep during the countdown. While in Self-Timer mode, you can also trigger a two-second countdown by pressing the Shutter button on the remote control, regardless of the self-timer delay chosen in the Record menu. Like several other cameras using infrared remote controls, there is no option for immediate shutter release when triggering the G5 from its remote. I confess I don't understand this, as I'd think that minimizing shutter lag would be a good thing, regardless of whether the camera is triggered from its own shutter button or via a remote control.
Interval Shooting
The G5 also features a built-in intervalometer, that lets you program the camera for extended time-lapse exposure sequences. You can choose intervals between successive photos ranging from one to 60 minutes, and anywhere from two 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 G5's Wireless Remote Control allows you to trigger the camera from as far away as 16.4 feet (5 meters) from the front sensor, and as far as 9.83 feet (3 meters) from the right side sensor. The range of the remote control will depend somewhat on ambient lighting and the angle you're at relative to the front of the camera. Range in bright sunlight will be much less than in a darkened room, and you'll get more range when you're directly in front of the camera than when you're to one side. The G5 lets you set the shutter delay when using the remote to zero, two, or ten seconds. (The no-delay option is particularly welcome, as most digicams with IR remotes have a minimum delay of two or three 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. With the LCD monitor rotated so that it faces you, you can use the Zoom buttons on the remote control to compose the image and the Display button to scroll through the LCD information screens 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, very handy for presentations using the built-in video output.
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