Pentax smc -FA Operating Manual page 15

How to Use the Lens Hood with polarizing
filter window
1. Remove the PL filter window cap by sliding
it in the direction shown.
The hood is designed for use with a polar-
izing filter or circular polarizing filter, and
includes a "PL filter window" for adjusting
the polarizing effect.
When attaching the hood, align the white
dots on the lens and hood so that the PL
filter window positions on the bottom.
2. Turn the outer rim of the polarizing filter or
circular polarizing filter from the PL filter
window as shown.
3. Attach the PL filter window cap.
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