The Canon EOS Digital Rebel XSi/450D Companion

CHAPTER 7

USING PRIORITY MODES TO CONTROL EXPOSURE

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e same image as before, this time shot with a tungsten white balance. Notice

that the separate channels are now shifted away from each other.

Using Priority Modes to Control Exposure

While the Exposure Compensation and Program Shift are both great ways to con-

trol exposure, there will be times when you’ll want more direct control. Shutter

and Aperture priority let you select specific shutter speeds or apertures and leave

the camera on those settings. So, for example, if you’re shooting landscapes and

know that you’re going to want a deep depth of field all day long, you can set the

camera on Aperture Priority, dial in f/11, and be assured that every shot will be

taken with that aperture.

Or, if you’re shooting a sporting event and know that you want lots of motion-

stopping power, you can select Shutter Priority and set the shutter speed to

something quick, like 1/1000th of a second.

Aperture Priority

To use Aperture Priority, set the XSi’s Mode dial to Av. In Aperture Priority mode,

you select the aperture you want, and the camera automatically chooses an ap-

propriate shutter speed, based on its metering.

In Aperture Priority mode, the rear LCD will display the current aperture setting

in a gray box, with arrows on both sides to indicate that you can change this

parameter. Turn the Main dial to change the aper