A-DEP is a simplified version of a related mode found in some higher-end Canon digital and film models called DEP. DEP allows you to manually select the nearest and farthest points you want in focus, and the camera will then adjust the focus point to a setting known as the hypefocal distance. At the hyperfocal distance, everything from half that distance to infinity will be in acceptable focus.
Although many photographers elect to set hyperfocal distance themselves, the exact distance varies by the lens focal length and aperture selected, so, unless you carry a hyperfo-cal distance chart around with you, it's usually easy to let A-DEP do its simplified calculations (you don't get to choose the near/far focus points) for you. Both DEP and A-DEP were developed around the time depth-of-field scales were starting to be omitted from lenses. While DOF scales can show you the approximate near and far acceptable focus points, as zoom lenses replaced fixed focal length (or prime lenses, as discussed in Chapter 7), such scales became too complicated for easy use. Thus, we have A-DEP as a "replacement."
In Av mode, you specify the lens opening used, and the T2i selects the shutter speed. Aperture-priority is especially good when you want to use a particular lens opening to achieve a desired effect. Perhaps you'd like to use the smallest f/stop possible to maximize depth-of-field in a close-up picture. Or, you might want to use a large f/stop to throw everything except your main subject out of focus, as in Figure 4.14, in which the musician in the foreground is in sharp focus, but his two mates in the background are out of focus. Maybe you'd just like to "lock in" a particular f/stop because it's the sharpest available aperture with that lens. Or, you might prefer to use, say, f/2.8 on a lens with a maximum aperture of f/1.4, because you want the best compromise between speed and sharpness.
Aperture-priority can even be used to specify a range of shutter speeds you want to use under varying lighting conditions, which seems almost contradictory. But think about it. You're shooting a soccer game outdoors with a telephoto lens and want a relatively high shutter speed, but you don't care if the speed changes a little should the sun duck behind a cloud. Set your T2i to Av, and adjust the aperture until a shutter speed of, say, 1/1,000th second is selected at your current ISO setting. (In bright sunlight at ISO 400, that aperture is likely to be around f/11.) Then, go ahead and shoot, knowing that your T2i will maintain that f/11 aperture (for sufficient DOF as the soccer players move about the field), but will drop down to 1/750th or 1/500th second if necessary should the lighting change a little.
A blinking 30 or 4000 shutter speed in the viewfinder indicates that the T2i is unable to select an appropriate shutter speed at the selected aperture and that over- and underexposure will occur at the current ISO setting. That's the major pitfall of using Av: you might select an f/stop that is too small or too large to allow an optimal exposure with the available shutter speeds. For example, if you choose f/2.8 as your aperture and the illumination is quite bright (say, at the beach or in snow), even your camera's fastest shutter speed might not be able to cut down the amount of light reaching the sensor to provide the right exposure. Or, if you select f/8 in a dimly lit room, you might find yourself shooting with a very slow shutter speed that can cause blurring from subject movement or camera shake. Aperture-priority is best used by those with a bit of experience in choosing settings. Many seasoned photographers leave their T2i set on Av all the time.
Shutter-priority (Tv) is the inverse of aperture-priority: you choose the shutter speed you'd like to use, and the camera's metering system selects the appropriate f/stop. Perhaps you're shooting action photos and you want to use the absolute fastest shutter speed available with your camera; in other cases. you might want to use a slow shutter speed to add some blur to a sports photo that would be mundane if the action were completely frozen. Or, you might want to give a feeling of motion and excitement, as with another concert photo seen in Figure 4.15. Shutter-priority mode gives you some control over how much action-freezing capability your digital camera brings to bear in a particular situation.
Lock the shutter at a slow speed to introduce creative blur, as with this image of a musician.
Lock the shutter at a slow speed to introduce creative blur, as with this image of a musician.
You'll also encounter the same problem as with aperture-priority when you select a shutter speed that's too long or too short for correct exposure under some conditions. I've shot outdoor soccer games on sunny Fall evenings and used shutter-priority mode to lock in a 1/1,000th second shutter speed, only to find my T2i refused to shoot when the sun dipped behind some trees and there was no longer enough light to shoot at that speed, even with the lens wide open.
Like Av mode, it's possible to choose an inappropriate shutter speed. If that's the case, the maximum aperture of your lens (to indicate underexposure) or the minimum aperture (to indicate overexposure) will blink.
Program mode (P) uses the T2i's built-in smarts to select the correct f/stop and shutter speed using a database of picture information that tells it which combination of shutter speed and aperture will work best for a particular photo. If the correct exposure cannot be achieved at the current ISO setting, the shutter speed indicator in the viewfinder will blink 30 or 4000, indicating under- or overexposure (respectively). You can then boost or reduce the ISO to increase or decrease sensitivity.
The T2i's recommended exposure can be overridden if you want. Use the EV setting feature (described later, because it also applies to Tv and Av modes) to add or subtract exposure from the metered value. And, as I mentioned earlier in this chapter, you can change from the recommended setting to an equivalent setting (as shown in Table 4.1) that produces the same exposure, but using a different combination of f/stop and shutter speed. To accomplish this
1. Press the shutter release halfway to lock in the current base exposure, or press the AE lock button (*) on the back of the camera (in which case the * indicator will illuminate in the viewfinder to show that the exposure has been locked).
2. Spin the Main Dial to change the shutter speed (the T2i will adjust the f/stop to match).
Your adjustment remains in force for a single exposure; if you want to change from the recommended settings for the next exposure, you'll need to repeat those steps.
Sometimes you'll want more or less exposure than indicated by the T2i's metering system. Perhaps you want to underexpose to create a silhouette effect, or overexpose to produce a high key look. It's easy to use the T2i's exposure compensation system to override the exposure recommendations, available in any Creative Zone mode except manual. There are two ways to make exposure value (EV) changes with the Rebel T2i. One method is fast and a bit clumsy to use, especially if your fingers aren't well coordinated.
The other method takes a few seconds longer, but can be done smoothly by the most fumble-fingered among us.
Activate the exposure meters by tapping the shutter release button. Then, just hold down the AV button (located on the back next to the upper-right corner of the LCD) and rotate the Main Dial to the right to make the image brighter (add exposure), and to the left to make the image darker (subtract exposure). The exposure scale in the viewfinder and on the LCD indicates the EV change you've made. The EV change you've made remains for the exposures that follow, until you manually zero out the EV setting with the AV button + Main Dial. EV changes are ignored when using M or any of the Basic Zone modes.
If you find yourself not turning the Main Dial quickly enough after you tap the shutter release button, try the second method for making EV changes with the T2i. It can be a little slower, but gives you more time to dial in your EV adjustment. You also have the option of setting exposure bracketing at the same time:
1. Press the Menu button and navigate to the Expo. Comp./AEB entry on the Shooting 2 menu.
2. When the screen appears, press the left/right cross keys to add or subtract EV adjustment. The screen has helpful labels (Darker on the left and Brighter on the right) to make sure you're adding/subtracting when you really want to. Note that you can also set exposure bracketing, as discussed in Chapter 3, by rotating the Main Dial while viewing this screen.
3. Press Set to confirm your choice.
Part of being an experienced photographer comes from knowing when to rely on your Rebel T2i's automation (including P mode and Basic Zone settings), when to go semiautomatic (with Tv or Av), and when to set exposure manually (using M). Some photographers actually prefer to set their exposure manually, as the T2i will be happy to provide an indication of when its metering system judges your manual settings provide the proper exposure, using the analog exposure scale at the bottom of the viewfinder and on the status LCD.
Manual exposure can come in handy in some situations. You might be taking a silhouette photo and find that none of the exposure modes or EV correction features give you exactly the effect you want. For example, when I shot the ballet dancer in Figure 4.16 in front of a mostly dark background highlighted by an illuminated curtain off to the
right, there was no way any of my Rebel T2i's exposure modes would be able to interpret the scene the way I wanted to shoot it, even with spot metering, which didn't have a narrow enough field-of-view from my position. So, I took a couple test exposures, and set the exposure manually using the exact shutter speed and f/stop I needed. You might be working in a studio environment using multiple flash units. The additional flash are triggered by slave devices (gadgets that set off the flash when they sense the light from another flash, or, perhaps from a radio or infrared remote control). Your camera's exposure meter doesn't compensate for the extra illumination, and can't interpret the flash exposure at all, so you need to set the aperture manually.
Because, depending on your proclivities, you might not need to set exposure manually very often, you should still make sure you understand how it works. Fortunately, the Rebel T2i makes setting exposure manually very easy. Just set the Mode Dial to M, turn the Main Dial to set the shutter speed, and hold down the Av button while rotating the Main Dial to adjust the aperture. Press the shutter release halfway or press the AE lock button, and the exposure scale in the viewfinder shows you how far your chosen setting diverges from the metered exposure.
The final tools in your exposure repertoire are the seven Basic Zone shooting modes, which can automatically make all the basic settings needed for certain types of shooting situations, such as portraits, landscapes, close-ups, sports, night portraits, and "no-flash zone" pictures. These "autopilot" modes are especially useful when you suddenly encounter a picture-taking opportunity and don't have time to decide exactly which Creative Zone mode you want to use. Instead, you can spin the Mode Dial to the appropriate Basic Zone mode and fire away, knowing that, at least, you have a fighting chance of getting a good or usable photo.
Basic Zone modes are also helpful when you're just learning to use your T2i. Once you've learned how to operate your camera, you'll probably prefer one of the Creative Zone modes that provide more control over shooting options. The Basic Zone scene modes may give you few options or none at all. The AF mode, drive mode, and metering mode are all set for you. Here are the modes available (I'll cover Creative Auto separately):
■ Full Auto. This is the mode to use when you hand your camera to a total stranger and ask him or her to take your picture posing in front of the Eiffel Tower. All the photographer has to do is press the shutter release button. Every other decision is made by the camera's electronics.
■ Portrait. This mode tends to use wider f/stops and faster shutter speeds, providing blurred backgrounds and images with no camera shake. If you hold the shutter release down, the T2i will take a continuous sequence of photos, which can be useful in capturing fleeting expressions in portrait situations.
■ Landscape. The T2i tries to use smaller f/stops for more depth-of-field, and boosts saturation slightly for richer colors.
■ Close-up. This mode is similar to the Portrait setting, with wider f/stops to isolate your close-up subjects, and high shutter speeds to eliminate the camera shake that's accentuated at close focusing distances. However, if you have your camera mounted on a tripod or are using an image-stabilized (IS) lens, you might want to use the Creative Zone aperture-priority (Av) mode instead, so you can specify a smaller f/stop with additional depth-of-field.
■ Sports. In this mode, the T2i tries to use high shutter speeds to freeze action, switches to high-speed continuous shooting to allow taking a quick sequence of pictures with one press of the shutter release, and uses AI Servo AF to continually refo-cus as your subject moves around in the frame. You can find more information on autofocus options in Chapter 5.
■ Night Portrait. Combines flash with ambient light to produce an image that is mainly illuminated by the flash, but the background is exposed by the available light. This mode uses longer exposures, so a tripod, monopod, or image-stabilized lens is a must.
■ Flash Off. Absolutely prevents the flash from flipping up and firing, which you might want in some situations, such as religious ceremonies, museums, classical music concerts, and your double-naught spy activities. This mode is identical to Full Auto, but with the flash disabled.
This mode is a hybrid between the Basic Zone Auto mode, and the Creative Zone Program mode. When you've selected this mode, the T2i makes most of the exposure decisions for you (just as in true Auto mode), but allows you to make some adjustments to other parameters, as described next.
When you set the Mode Dial to the CA position, a screen resembling the one shown in Figure 4.17 appears (the currently set shutter speed and aperture appear only when the exposure meters are activated; turn them on by tapping the shutter release). The basic settings are the same as those produced by the Full Auto Basic Zone mode. Just follow these steps:
1. Press the Q button to switch into shooting settings mode.
2. Use the cross keys to navigate to the setting you want to change. A description of that setting appears at the bottom of the screen when that option is highlighted.
3. Press the Set button to activate the setting.
4. Use the Main Dial to choose the options for the setting you have chosen.
5. Press the Set button to confirm your choice.
6. Tap the shutter release to exit the settings mode. The settings you may adjust include
■ Blur/sharpen background. Rotate the Main Dial to the left to blur the background (which causes the T2i to select a larger f/stop for the same exposure), or towards the right to sharpen the background (ending up with a smaller f/stop for the same exposure).
■ Adjust image brightness. Rotate the Main Dial to the left to reduce the overall exposure, making the image darker, or towards the right to increase exposure and make the image brighter.
Shutter speed Aperture (appear when meters are active)
Flash firing Picture mode Style
In Creative Auto mode, this screen appears to allow making quick adjustments to some parameters.
Background blurring/ sharpening
Shutter speed Aperture (appear when meters are active)
Flash firing Picture mode Style
■ Picture Style. You can select Standard, Portrait, Landscape, or Monochrome Picture Styles, which, in the Creative Auto mode are equated to "standard images," "smooth skin tones," "vivid blues and greens," and "monochrome image." (The actual name of the Picture Style is not shown, and the other pre-set styles, plus User Def styles are not available from this screen in Creative Auto mode.)
■ Drive mode. You can switch from single, continuous, or self-timer drive modes.
■ Image quality. When you highlight this section, you can use the Main Dial to cycle among the various combinations of image size/JPEG quality/RAW options.
Another way of adjusting exposures is by changing the ISO sensitivity setting. Sometimes photographers forget about this option, because the common practice is to set the ISO once for a particular shooting session (say, at ISO 100 or 200 for bright sunlight outdoors, or ISO 800 when shooting indoors) and then forget about ISO. ISOs higher than ISO 100 or 200 are seen as "bad" or "necessary evils." However, changing the ISO is a valid way of adjusting exposure settings, particularly with the Canon EOS
Rebel T2i, which produces good results at ISO settings that create grainy, unusable pictures with some other camera models.
Indeed, I find myself using ISO adjustment as a convenient alternate way of adding or subtracting EV when shooting in manual mode, and as a quick way of choosing equivalent exposures when in automatic or semi-automatic modes. For example, I've selected a manual exposure with both f/stop and shutter speed suitable for my image using, say, ISO 200. I can change the exposure in full-stop increments by pressing the ISO button on top of the camera, and spinning the Main Dial one click at a time. The difference in image quality/noise at the base setting of ISO 200 is negligible if I dial in ISO 100 to reduce exposure a little, or change to ISO 400 to increase exposure. I keep my preferred f/stop and shutter speed, but still adjust the exposure.
Or, perhaps, I am using Tv mode and the metered exposure at ISO 200 is 1/500th second at f/11. If I decide on the spur of the moment I'd rather use 1/500th second at f/8, I can press the ISO button and spin the Main Dial to switch to ISO 100. Of course, it's a good idea to monitor your ISO changes, so you don't end up at ISO 1600 accidentally. ISO settings can, of course, also be used to boost or reduce sensitivity in particular shooting situations. The Rebel T2i can use ISO settings from ISO 100 up to 12800 when you're choosing a sensitivity manually and you've selected the Expanded ISO range, as described in Chapter 3. The camera will choose ISO 100 to 6400 automatically in Basic Zone modes or from ISO 100 to 3200 in Creative Zone Auto mode— and up to 12800 with the Expanded ISO range available.
The camera can adjust the ISO automatically as appropriate for various lighting conditions. In Basic Zone modes, ISO is normally set between ISO 100-3200. When you choose the Auto ISO setting, the T2i adjusts the sensitivity dynamically to suit the subject matter. In Basic Zone Auto, Landscape, Close-Up, Sports, Night Portrait, and Flash Off modes, the T2i adjusts ISO between ISO 100 and 3200 as required. In Portrait mode, ISO is fixed at ISO 100, because the T2i attempts to use larger f/stops to blur the background, and the lower ISO setting lends itself to those larger stops.
When Auto ISO is chosen when using Creative Zone modes, sensitivity will be generally set to ISO 100-6400 in Program, Av, Tv, M, and A-DEP modes. In manual exposure mode, Auto ISO is fixed at ISO 400.
When using flash, Auto ISO produces a setting of ISO 400 automatically, except when overexposure would occur (as when shooting subjects very close to the camera), in which case a lower setting (down to ISO 100) will be used. If you have an external dedicated flash attached, the T2i can set ISO in the range 400-1600 automatically. That capability can be useful when shooting outdoor field sports at night and other "long distance" flash pictures, particularly with a telephoto lens, because you want to extend the "reach" of your external flash as far as possible (to dozens of feet or more), and boosting the ISO does that. Remember that if the Auto ISO ranges aren't suitable for you, individual ISO values can also be selected in any of the Creative Zone modes.
Find yourself locked out of ISO settings lower than 200? Check C.Fn II-06 Highlight tone priority. When set to 1: Enable, only ISO 200-1600 can be selected.
Bracketing is a method for shooting several consecutive exposures using different settings, as a way of improving the odds that one will be exactly right. Before digital cameras took over the universe, it was common to bracket exposures, shooting, say, a series of three photos at 1/125th second, but varying the f/stop from f/8 to f/11 to f/16. In practice, smaller than whole-stop increments were used for greater precision. Plus, it was just as common to keep the same aperture and vary the shutter speed, although in the days before electronic shutters, film cameras often had only whole increment shutter speeds available.
Today, cameras like the T2i can bracket exposures much more precisely, and bracket white balance as well. While WB bracketing is sometimes used when getting color absolutely correct in the camera is important, auto exposure bracketing (AEB) is used much more often. When this feature is activated, the T2i takes three consecutive photos: one at the metered "correct" exposure, one with less exposure, and one with more exposure, using an increment of your choice up to plus 2/minus 2 stops. (Choose between increments by setting Custom Function I-01 to 0 [1/3 stop] or 1 [1/2 stop].) In Av mode, the shutter speed will change, whereas in Tv mode, the aperture speed will change.
Using AEB is trickier than it needs to be, but has been made more flexible with the upgrade from the Rebel XSi's bracketing system. (With the T2i you can now choose to bracket only overexposures or underexposures—a very useful improvement!) Just follow these steps:
1. Activate the EV/AEB screen. Press the Menu button and navigate to the Shooting 2 menu, where you'll find the Expo. comp/AEB option. Press Set to select this choice.
2. Set the bracket range. Rotate the Main Dial to spread out or contract the three dots to include the desired range you want to cover. For example, with the dots clustered tightly together, the three bracketed exposures will be spread out over a single stop. Separating the cluster produces a wider range and larger exposure change between the three shots in the bracket set, as shown in Figure 4.18.
Exposure comp./AEB setting
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