Pentax K20D User Manual page 90

Using the c (Aperture Priority) Mode
Set 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.
1Effect of Aperture and Shutter Speed (p.76)
1
Set the mode dial to c.
2
Turn the rear e-dial and adjust
the aperture value.
The shutter speed and aperture value
are displayed in the viewfinder and on
the LCD panel.
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4