Clamp Screw - Pentax smc -FA Operating Manual

Clamp Screw

FA Macro 50mm f/2.8 and 100mm f/2.8 lens-
es are equipped with a clamp screw that is
used when focusing manually. With manual
close-up photography using the copy stand in
any situation or with the lens pointing down ,
if you turn the clamp screw to the ON posi-
tion, rotation of the focusing ring becomes
tight. This helps to prevent the rotation of the
focusing ring due to the lens's own weight
and avoid any shift in focus.
When shooting in the autofocus mode, turn
the clamp screw to the OFF position.
Activating the autofocus mode while the
clamp screw is in the ON position slows
down the focusing speed.
CLAMP
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