The two Sigma TC-1411 and TC-2011 teleconverters have been developed exclusively for use with Sigma lenses for mirrorless cameras. The outstanding optical performance of Sigma lenses from the Contemporary, Art and Sports product lines is the result of Sigma's commitment to the highest image quality. The Sigma TC-1411 and TC-2011 tele-converters maintain the image quality of the lens to a high degree and simultaneously extend the focal length. Mounted between the lens and camera body, the TC-1411 increases the focal length of the camera by a factor of 1.4 and the TC-2011 by a factor of 2. The teleconverters are also designed to be dust and splash-proof, comparable to the lenses in the Sports line, and can therefore be used in conjunction with dust and splash-proof camera bodies and lenses in harsh conditions. Tele-converters are easy to use and represent a favourable alternative to a larger, more expensive telephoto lens, as they provide an "ultra-tele" angle of view for the compatible telephoto and macro lenses while retaining the performance of the combined lens.