Infinity Compensation Mark
To compensate for shifting of the infinity focus point that results from changes in temperature, there is a margin at the infinity (∞) position.
The infinity position at normal temperature is the point at which the vertical line of the distance scale
![](/library/CANON/CITS_TECH_SUPPORT/Camera/Lenses/EF%20400mm%20F2.8L%20IS%20III%20USM/mark.png)
mark is aligned with the distance index.
![](/library/CANON/CITS_TECH_SUPPORT/Camera/Lenses/EF%20400mm%20F2.8L%20IS%20III%20USM/warning.png) |
For accurate focusing in MF on subjects at infinity distance, look through the viewfinder while rotating the focusing ring. |