9.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 distance scale L mark is aligned with the distance index.
For accurate focusing in MF on subjects at infinity distance, look through the viewfinder while rotating the focusing ring.
10. Hood
The special hoods that come with all these lenses cut out unwanted light and protect the front of the lens from rain, snow, and dust.
To attach the hood, loosen the hood lock knob by turning it counterclockwise. Fit the hood onto the lens’s hood mount, and tighten the lock knob to fix it in place. Use the same procedure, in reverse, to remove the hood.