Apple Macintosh Performa 577 - Manual (Page 147)

Adjustments Light Meter Setup - 26
Model 246
1 Remove the metal slide,
if installed, from the
top of the light meter.
2 Install the white lens
with the red dot.
3 Rotate the swivel head
so the lens of the meter
faces the monitor.
4 Place the lens against the
middle of the screen and
read the scale.
Lens
Swivel Head
Scale