Nikon SMZ1500 Instructions Manual page 27

Illuminator
g The optical axis of the 1/4 lambda plate is at
the 45° position from the red dot. Brightness
is the maximum when the red dot is
positioned at the front and switches from
bright to dark by each 45° position. Adjust
the plate to the position where the brightness
and contrast are best suited for the
observation.
Bright
Dark Dark
Bright Bright
Dark Dark
Bright
Insert the filter P-ICI33 NCB 14 into the fiber
illuminator to improve the color
reproducibility when taking a
photomicrogaph. Refer to the instruction
manual of Fiber Illuminator.