Pentax K10D Operating Manual page 152

150
Using the b (Shutter Priority) Mode
Set the shutter speed faster and capture fast moving subjects as if they are
still or slow down the shutter speed and capture images emphasizing
subject movement.
Aperture value is automatically set to give the appropriate exposure
depending on the shutter speed.
1 Effect of Aperture and Shutter Speed (p.138)
1
Set the mode dial to b.
4
2
Turn the front e-dial and adjust
the shutter speed.
The shutter speed and aperture value
are displayed in the viewfinder and on the
LCD panel.