Pentax Optio H90 Orange Operating Manual page 70

Using the Shutter Release Button
The shutter release button works in a two-step action as follows.
Press halfway
This refers to pressing the shutter release button gently to the first
position. This locks the focus setting and the exposure. The green focus
frame lights on the display when the shutter release button is pressed
halfway and the subject is in focus. If the subject is out of focus, the
frame turns white.
Press fully
3
This refers to pressing the shutter release button all the way down to the
fully depressed position. This takes a picture.
Poor focusing conditions
The camera may not be able to focus under the following conditions. In these
cases, lock the focus on an object the same distance away as the subject (by
pressing and holding the shutter release button halfway), then aim the camera
at your subject and press the shutter release button fully.
• Objects that lack contrast such as a blue sky or white wall
• Dark places or objects, or conditions that prevent light being reflected back
• Horizontal lines or intricate patterns
• Fast moving objects
• When there is an object in the foreground and an object in the background in
the captured area
• Strongly reflected light or strong backlighting (bright background)
68
Not pressed Pressed halfway
(first position)
Pressed fully
(second position)