The 1.4X APO Tele Converter EX DG from Sigma is attached to the master lens to increase its focal length by 1.4 times. Featuring an Aperture coupling range of F2.8 - F32, the APO Tele Converter EX decreases the effective aperture by one F-stop. This tele-converter employs lens coating technology to reduce both flare and ghosting. Compact and lightweight, this tele-converter has a lens construction and is designed for use with select Canon Mounts.