Canon RF-S3.9 mm F3.5 STM DUAL FISHEYE Instructions Manual page 13

Checking/adjusting left and right focus
Adjusting left and right focus
Leaving the enlarged image from the right lens showing, adjust using the following steps.
Left-right focus difference adjustment mode switch
1
Slide the left-right focus difference
adjustment mode switch to the ADJUST
side.
Focusing/Control ring
2
Turn the focusing/control ring to adjust.
Turning the focusing/control ring only adjusts the
z
focus of the right lens.
Adjustment is complete once the focus in the
z
enlarged image from the right lens is correct.
After adjustment, return the left-right focus
z
difference adjustment mode switch back to its
original position (the opposite side to ADJUST).
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