High Quality Optics. The Canon 1.4x Teleconverter III features three groups of seven elements that ensure improved optical performance. All optical elements use Canon’s super-spectra coating, which reduces ghosting and flare to minimize post-processing requirements and a fluorine coating on the front and rear elements makes smudge marks much easier to clean.

Full Electronic Pass-Through. The extender features an integrated processor which ensures all focusing, metering, and ID information is available. Canon claims that, when combined with the range of premium Canon L-series lenses, these extenders enable higher AF accuracy.