Built-In Lens Hood; Filter Mounting Thread - Canon EF 300mm f/4L IS USM Instruction

8. Hood
The built-in lens hood can reduce unwanted
reflections and also protects the front of the lens
from rain, snow, dust, and other substances.
When using the hood, extend it outward from the
end of the lens until it stops and then turn it in
the direction of the arrow. For storage, reverse
the procedure.
9. Filters
(Sold separately)
You can attach filters to the filter mounting thread
on the front of the lens.
• If you need a polarizing filter, use the Canon
Circular Polarizing Filter (77mm).
• To adjust the polarizing filter, first store the lens
hood.
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