Advance Exposure Modes on the Canon EOS Rebel T7i/800D

With your Canon EOS Rebel T7i/800D camera in certain Basic Zone modes, including Creative Auto and certain Scene modes, you can affect exposure and depth of field to some extent. But if you're really concerned with these picture characteristics — and you should be — set the Mode dial to one of the four Creative Zone exposure modes highlighted here. In these modes, you get more precise control over aperture, shutter speed, and other exposure features.

Each of the four exposure modes — known collectively as Creative Zone modes in Canon lingo — offers a different level of control over aperture and shutter speed.

• P (programmed autoexposure): The camera selects both the aperture and shutter speed to deliver a good exposure at the current ISO setting. But you can choose from different combinations of the two for creative flexibility (which is why this mode is sometimes referred to generically as flexible programmed autoexposure).
• Tv (shutter‐priority autoexposure): You select a shutter speed, and the camera chooses the aperture setting that produces a good exposure at that shutter speed and the current ISO setting.

  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 gives you control over the aperture setting — thus Av, for aperture value. The camera then selects the appropriate shutter speed to properly expose the picture — again, based on the selected ISO setting.
• M (manual exposure): In this mode, you specify both shutter speed and aperture.

To sum up, the first three modes are semiautomatic modes that offer exposure assistance while still providing some creative control. Note one important point about these modes, however: In extreme lighting conditions, the camera may not be able to select settings that will produce a good exposure, but it doesn't stop you from taking a poorly exposed photo. You may be able to solve the problem by using features designed to modify autoexposure results, such as Exposure Compensation (explained later in this chapter), or by adding flash, but you get no guarantees.

Manual mode puts all exposure control in your hands. If you're a longtime photographer who comes from the days when manual exposure was the only game in town, you may prefer to stick with this mode. If it ain't broke, don't fix it, as they say. And in some ways, manual mode is simpler than the semiautomatic modes — if you're not happy with the exposure, you just change the aperture, shutter speed, or ISO setting and shoot again. You don't have to fiddle with features that enable you to modify the results delivered by the modes that use autoexposure (P, Tv, and Av).

Whichever mode you choose, check out the next several sections to find out how to view and adjust the various exposure settings.