Olympus iS-3 DLX Instructions Manual page 50

You can expose two images on a single frame.
Select the Double
Exposure mode to
display
LCD panel.
50
DOUBLE EXPOSURE
on the
D.EXP.
D.EXP.
Press the shutter release
button fully to take the
first exposure.
Make sure
on the LCD panel will blink.
D.EXP.
The film will not be advanced.