Aperture-Priority Ae (Av); You Set The Aperture - Canon EOS-3 Instructions Manual

2. Aperture-Priority AE (Av):

You Set the Aperture

In this mode, you set the desired aperture and the camera sets the
shutter speed automatically to suit the subject brightness.
The larger the aperture (smaller F-number like f/1.4) the more blurred the
background will be. This effect is suited for portraits. The smaller the
aperture (larger F-number like f/22), the clearer the focus will be for both
near and far objects.
Av is an abbreviation for Aperture value.
With a large aperture With a small aperture
1
While pressing the <
button, turn the <
appears on the LCD panel.
>
> dial until Av
65