Canon 310XL Instructions Manual page 16

Exposure Adjustment When Shooting Against the Light
The exposure control plate is used in order to attain
the correct exposure when shooting against strong
direct light such as when the sun is behind the
subject. Exposure adjustment value is approximate¬
ly 2 f/stops. When shooting a subject with a window
in the background or in ordinary light conditions,
exposure adjustment is not necessary.
Pull the shutter release lever and shoot
Press the zooming switch when necessary. Zooming
can be used for composition or to make the image
change continuously. Power zooming or manual
zooming are both possible.
Power Zooming
-j While pulling the shutter release lever, press the
zooming switch.
2 The subject will become larger when
"T"
is
pressed, and smaller when "W'^ is pressed.
When the image stops moving, the zooming lever
will not rotate anymore.
Keep the light metering window uncovered while
you operate the power zooming. Power zooming
cannot be performed without pulling the shutter
release lever.