Extending the effective focal length of select Tokina and Canon EF-mount lenses, this Kenko TELEPLUS HD pro 1.4x DGX Teleconverter enables you to get even more reach out of your lenses. The dedicated design retains full communication between the lens and Canon EF-mount cameras in order to maintain auto-exposure metering and autofocus capabilities. These contacts also relay Exif data between the attached lens and camera, and convert the data to the actual focal length in use with the teleconverter attached. This 1.4x teleconverter effectively increases your focal length by 40% and has a light loss of one stop. Additionally, the advanced optical design features five elements in four groups, and a multi-layer anti-reflective coating has been applied to individual elements to reduce flare and ghosting for improved contrast and color rendering.