The lens also features weather-sealed construction, but apart from the seal around the mount, it’s unclear if there is extensive sealing elsewhere.
With no change to the optical construction, the new model performs practically identically to its predecessor. However, the new T* coatings have improved transmission slightly, which in turn lowers flare and improves contrast and perceived sharpness, as evidenced in the increase in the overall sharpness metric, but it’s slight and may be noticed only in the lab, rather than the field.
Canon EF mount
Constant f/2 maximum aperture
Lens made of special glass with anomalous partial dispersion