Pentax ist d 사용자 설명서

4

The appropriate aperture value is automatically set by the camera for a 
proper exposure to match the brightness of the subject when the shutter 
speed is selected.
This mode is suitable for freezing the action with a faster shutter speed or 
capturing a flowing dynamic image with a slower shutter speed. See page 
136 for the effect of shutter speed.

1

Set the mode dial to b.

2

3