Pentax SF10 Manual page 11

3. Remove the front lens cap by pressing in the tabs on
both sides.
^
To disengage the lens, turn the lens counterclockwise
while depressing the lens-lock release lever.
Note:
Do not damage or stain the lens information contacts
or the AF coupler on the mount surfaces of the camera
and the lens. If this occurs, wipe them gently with a clean
dry cloth.