Canon Microfilm Scanner 400 Instruction Manual page 15

Work safely!
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.
To adjust the light intensity for the lens installed, adjust the light
intensity to the color label for the lens shown on the lens label.
f a
b
e
c
d
Light adjustment dial
Lens Label
11