Canon Powershot G6By: Dave EtchellsThe next generation of Canon's popular "G" model updates the line with a larger, 7.1-megapixel CCD and a redesigned camera body. <<Optics :(Previous) | (Next): Shutter Lag & Cycle Time Tests>> Page 7:Exposure & FlashReview First Posted: 09/28/2004 |
Exposure
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The G6 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. In Program AE mode, a Program Shift
function allows you to bias the exposure for a faster shutter speed / wider
aperture, or a slower shutter speed / smaller aperture, by pressing the AE /
FE lock button, and then rolling the Main dial back and forth to select the
combination of aperture and shutter speed that you want to use.
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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. In Aperture Priority mode, the maximum shutter time is 1 second, and the minimum is limited to 1/1,250 for apertures of f/3.5 and under. 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 Main dial. Courtesy of a new Safety Shift option in the Record menu, the camera will (if selected) override your selected shutter / aperture setting in Shutter or Aperture Priority modes, should the metering system detects that the exposure will be incorrect with your selected setting. In Manual mode, the Main dial adjusts both settings, you just press down on it to alternate between aperture and shutter speed. (A very convenient way to control both variables with a single control.) In Manual mode, the maximum shutter time of 15 seconds is available, but the same restriction to 1/1,250 or below for apertures of f/3.5 and under remains in effect. (This is a consequence of the interaction between the G6's shutter mechanism and the lens aperture.)
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 "Function / Delete" button, which pulls up a small erase menu on the bottom of the monitor. Press the Set button to complete the erasure, or the Right arrow button to highlight "Cancel", followed by the Set button, should you change your mind.
Just as on the G3 and G5, the G6 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 Flash 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 ñ2 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, with a particular bias towards a reading from the center of the frame. 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 G6 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.
As you'd expect, image noise in the G6's images increases with increasing ISO, but I found the G6's noise to be less objectionable than that from many competing cameras. The amplitude of the image noise has been reduced from what it was in the prior G5 model, bringing it in line with the current crop of high-end prosumer digicams from a range of manufacturers. While the G6's image noise is roughly on par with other high-end digicams in terms of its absolute magnitude, it has a finer-grained texture than is common among prosumer digicams, which makes it less evident to the eye. The net result is that, while its ISO 400 images are indeed noisy, their appearance is such that I wouldn't mind shooting with the G6 at that ISO level, something I can't say for many non-SLR digicams these days.
Flash
The G6'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 front left-hand corner of the G6's top 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 G6'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 G6 features a hot shoe for mounting more powerful external flash units. Canon recommends using its own Speedlight 220EX, 420EX, 550EX, 580EX, MT-24EX Macro Twin Light, or MR-14EX Macro Ring models, but other manufacturers' models should work as well. The G6's flash sync speed is a maximum of 1/250.
Canon's handling of the sync-speed limitation on the G6 bothers me a little though, as it did on the G3 and G5 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 G6 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, G3 and G5 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 G6 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 G6's Continuous Shooting mode captures multiple consecutive images at up to 1.6 frames per second (fps). This frame-capture rate may vary slightly, depending on image quality, and functions in use. (In my own testing, the G6 consistently delivered 1.05 frames/second, shooting either large or small JPEG images. Shooting in RAW+JPEG mode, the frame rate dropped to 0.68 frames/second.) The G6 will continue to capture images as long as the Shutter button is depressed, or until the camera's memory card is filled. Shooting slows after about 10 large/fine JPEG shots, or four RAW+Large JPEG frames.
Interestingly, I noticed that the tendency of the earlier G-series cameras to delay slightly longer between the first and second continuous-mode shots than between subsequent ones seems absent (or at least very much reduced) in the G6. The variation in interval between the first two shots and subsequent ones was within a few percent in my timing tests of the G6.
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 1.6 frames/second in my tests. As with the low-speed continuous mode, shooting RAW+JPEG slowed the high-speed mode frame rate to about 0.7 frames/second. (Virtually identical to the speed for that format option in low speed continuous mode.)
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. (About 8 large/fine JPEG shots, vs 10 for the low speed mode.)
As noted above, the G6 has a fairly generous buffer memory, able to capture 11 large/fine frames in rapid sequence in single-shot mode, 10 frames in low-speed continuous mode, and 8 in high-speed mode. RAW+JPEG buffer capacity is about 4 frames, still not bad. All of these numbers represent a fairly dramatic improvement over the relatively limited buffer capacity of the previous G5 model. (Four large/fine JPEG frames two RAW ones.)
Movie Mode
The G6 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 10 frames per second at a resolution of 640 x 480 pixels, or approximately 15 frames per second, with a choice of 320 x 240- and 160 x 120-pixel resolutions . Recordings can last as long as thirty seconds at the higher 640 x 480 pixel setting, or three minutes at either of the lower resolution settings, 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, preset Picture Effects, self-timer, wireless delay, ND filter, 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 or later is required to view the AVI/Motion JPEG files recorded by the G6 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. If you decide that you didn't align
the last image correctly, or are unhappy with it for any reason,
you don't need to reshoot the entire series - you can go back to
redo the last shot by pressing the left-arrow on the Four-Way Arrow
pad. You can also opt to change your mind once again, and keep the
previously recorded image, by pressing the right-arrow on the
Four-Way Arrow pad. 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 10-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 or ten-second
countdown by pressing the Shutter button on the remote control, or
to capture the shot immediately.
Interval Shooting
The G6 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 G6'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 3.3 feet (1 meter) 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 G6 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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