Apple Mac 5260/100 - Manual (Page 186)

5260 and 5280 Adjustments Light Meter Setup - 3
To measure a display
screen’s luminance,
1 Set the scale switch to
the bottom position (to
set up the 10-50 fc
scale).
2 Place the lens against the
middle of the screen and
read the bottom scale.
Note:
When the light meter
is not in use, slide the scale
switch to its top position,
and store the meter in its
protective case.
Important:
If you suspect the
light meter is giving false