The Leica Teleconverter 2x Apo Extender R (NON ROM) enlarges the central part of an image to increase the focal length of the primary lens, while reducing the intensity of light on the imaging receptor. The APO-Extender-R 2x doubles the focal length and results in two aperture stops in lens speed loss (a lens set to f/2.8 will become a f/5.6).