Leica's Hektor 28mm lens was an extreme wide angle lens (76º) introduced by Leitz around 1939. Hektor had an maximum aperture of f/6.3 and was made of six elements arranged in three groups with two cemented surfaces. Even at full aperture, which in a system of such large angle of view must be regarded as high, it gave remarkable sharpness to the Leica format without distortion, which was a novel feature in view of its very short focal length. In this lens, the requirement of extentive reduction of vignetting had been taken into consideration by making the lens larger than the dimension corresponding to the relative aperture. So, proper reduction of the aperture results in further increase of the quality of the image and an improved distribution of light over the entire image area.