Cutaway diagram of a Leica IIIa (1939) with Hektor 73mm and Elmar 50mm lenses.
Canon wide angle lenses
Canon High Speeds
Canon Normal 50 mm lens
Super-Multi-Coated TAKUMAR 1:2.8/105mm
Metabones Speed Booster Optical Diagram
In the East, Carl Zeiss Jena produced the f2 50mm Flexon/Pancolar less than a year after the Planar 2/50 using only 6 elements, same with the later 1.8/50 Pancolar.
Aldis Anastigmat - Antique and Vintage Cameras
Morrison's Wide Angle Lens, Early, c.1876