Canon Microfilm Scanner 300 Instruction Manual page 19

Light adjustment dial
2. Slide the other lens into the unit.
If you are using the FS Controller I, before you insert
the lens, remove the bottom cover of the lens as shown
in the illustration. Make sure you keep the cover and
install it on the lens again after it is removed from the
unit.
3. Turn the light adjustment dial to the left or right to adjust the
light intensity of the screen. Adjust the light intensity to the
type of lens installed.
Set the light intensity adjustment dial to the same mark that is
written on the label of the lens you are using.
I BEFORE YOU BEGIN ... I
Lens Label
17