Pentax SF1 Manual page 23

Exposure Mode Clear Button
Pushing this button instantly resets all the current settings
{exposure mode, drive mode, exposure compensation,
etc.) to the settings described below.
Exposure Lens at setting
Mode:
■ Normal
Program
Lens at any f-number
Aperture-
Priority AE
Drive Mode:
—► Single Advance
Exposure
Compensation:
±0.0