Canon EF 100mm f2.8L Macro IS USM - Manual (Page 7)

ENG-6
4. Infinity Compensation 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 of subjects at
infinity, look through the viewfinder or look at the
magnified image* on the LCD screen while
rotating the focusing ring.
* For cameras with Live View shooting capability.
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