Pentax K-7 Operating Manual page 104

Lets you set the desired aperture for controlling the depth of field. The
depth of field is deeper and the front and back of the focused object is clear
when aperture is set to a large value. The depth of field is shallower and
the front and back of the focused object is blurred when aperture is set to
a small value.
Shutter speed is automatically set to appropriate exposure depending on
the aperture value.
r-_ Effect of Aperture and Shutter Speed (p.88)
1 Set the mode dial to Av.
2
Turn the rear e-dial (%,_,,_) to
adjust the aperture.
Aperture range depends on the lens in
use.
The shutter speed and aperture value are displayed on the status screen
and LCD panel and in the viewfinder.
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