Pentax P5 - Page 37

When determining shutter speed first
Set the shutter speed you desire by pushing the UP
or DOWN button. As you turn the aperture ring
until the shutter-speed display in the viewfinder
changes from flickering to glowing, you can obtain
correct exposure. If you cannot obtain the indication
of correct exposure by changing the aperture, reset
the shutter speed.
When determining aperture first
Set the aperture you desire. As you change
the shutter-speed display changes the UP or DOWN
button until the shutter-speed display changes from
flickering to glowing, i.e., only the glowing speed
remains, you can obtain correct exposure. If you
cannot obtain the indication of correct exposure,
no matter how you change the shutter speed, reset
the aperture.