The Leica APO Extender 1.4X is made to be inserted between the camera and lens, and extend its focal length by a factor of 1.4. The Leica APO-Extender-R 1.4X, is of five-element construction and is designed for lenses with maximum apertures of 1:2.8 and below, and reduces the effective aperture by one stop. Lenses with a maximum aperture of 1:2 should therefore be stopped down by approximately one to two stops.