Priority modes
METERING is still automatic in Aperture Priority (Av) mode, but you select the aperture you want to use and the camera adjusts the shutter speed accordingly. It’s vice versa for Shutter Priority (Tv) mode, as you set the shutter speed and the camera adjusts the aperture. Beware of a blinking aperture or shutter speed display in the viewfinder, which indicates that you’ve set a value outside of the range that will enable a correct exposure in the prevailing lighting conditions.