Setting The Focus Mode; Infinity Distance Mark; Focusing Ring - Canon EF50mm F1.2L USM Instruction Manual

2. Setting the Focus Mode

To shoot in autofocus mode, set the focus mode
switch to AF.
To use only manual focusing, set the focus mode
switch to MF, and focus by turning the focusing
ring. The focusing ring always works, regardless
of the focus mode.
After autofocusing in ONE SHOT AF mode, focus
manually by pressing the shutter button halfway and
turning the focusing ring. (Full-time manual focus)
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3. Infinity Distance Mark

Infinity compensation mark
Distance index
To compensate for shifting of the infinity focus
point that results from changes in temperature.
The infinity position at normal temperature is the
point at which the vertical line of the L mark is
aligned with the distance indicator on the
distance scale.
For accurate manual focusing on subjects at
infinity distance, look through the viewfinder while
rotating the focusing ring.