Exploring Advanced Exposure Modes on a Canon EOS Rebel T3 Series Camera
To fully exploit your Canon Rebel T3 or T3i’s capabilities, you need to explore your camera’s five advanced exposure modes, represented on the Mode dial by the letters P, Tv, Av, M, and A-DEP.
Using these five modes lets you manipulate two critical exposure controls, aperture and shutter speed. That’s not a huge deal in terms of exposure; the camera typically gets that part of the picture right in the fully automatic modes. But changing the aperture setting also affects the distance over which focus is maintained (depth of field), and shutter speed determines whether movement of the subject or camera creates blur. Having input over these two settings provides you with a whole range of creative options that you don’t enjoy in the fully automatic modes.
Each of the five advanced modes offers a different level of control over aperture and shutter speed, as follows:
P (programmed autoexposure): The camera selects both the aperture and shutter speed for you, but you can choose from different combinations of the two.
Tv (shutter-priority autoexposure): You select a shutter speed, and the camera chooses the aperture setting that produces a good exposure.
Why Tv? Well, shutter speed controls exposure time; Tv stands for time value.
Av (aperture-priority autoexposure): The opposite of shutter-priority autoexposure, this mode asks you to select the aperture setting — thus Av, for aperture value. The camera then selects the appropriate shutter speed to properly expose the picture.
A-DEP (auto depth of field): In A-DEP mode, the camera assesses the distance between the lens and major objects in the frame and tries to choose an aperture setting that keeps all those objects within the zone of sharp focus. Then the camera sets the appropriate shutter speed for the aperture it selected.
Although this mode enables you to tell the camera that extending the depth of field to cover everything in the frame is your goal, there’s no guarantee that the camera will select the aperture setting you have in mind. In addition, when you use flash or enable Live View shooting, you lose the automatic depth-of-field feature, and A-DEP mode works just like P mode — but without giving you the benefit of being able to select from different combinations of aperture and shutter speed. So if you want to control depth of field but still enjoy autoexposure, you’re better off with Av mode.
M (manual exposure): In this mode, you specify both shutter speed and aperture. Although that prospect may sound intimidating, it’s actually the fastest and least complicated way to dial in exactly the exposure settings you want to use. And even in M mode, the camera assists you by displaying a meter that tells you whether your exposure settings are on target.
A quick reminder about a point that is often misunderstood: Setting the Mode dial to M has no effect on whether autofocusing or manual focusing is enabled. To choose your focusing method, use the switch on the lens. You can focus manually or use autofocus no matter what your exposure mode.