A little bit of history of the modern slr and dslr wide-angle lens design: it was invented and designed by a French man, P. Angenieux, whom some of you who are in the professional movie and broadcast industries may have heard of. His foray into the 35mm slr market was short-lived, spanning from 1950 into the 1960s-70s. As a matter of fact the word Retrofocus was Angenieux's own trade name, which for some unknown reason has now been highjacked by others. Prior to 1950 there was no wide-angle lenses for the slr 35mm format, because the mirror got in the way. Angenieux designed his retrofocus lens as a reversed telephoto design whose effective focal length is less than its backfocus (distance between the rear lens element and the image plane). This allowed for the first time the design of wide-angle lenses for slr cameras, which in the past was not possible because conventional wide-angle lenses had some lens element protruding into the camera body. This first pioneer wide-angle lens was the P. Angenieux 35mm f/2.5 lens that later found its way into many camera brands. More Angenieux lenses followed: 28mm f/3.5, 24mm f/3.5, 50mm f/1.5 and f/1.8, 90mm f/1.8 and f/2.5, 135mm f/2.5 and f/3.5 and 180mm f/4.5. In the 1960s Angenieux went into the zoom lenses business and made many famous zoom lenses for Munolta, Leica, etc. However, seeing the fierce competition from the East it wisely decided to concentrate in its area of strength-military, movie and broadcasting, medical, and space-programs lens markets. I believe it sold its 35mm lens business to Tokina many years ago. Since some of you have modern digital cameras that have smaller 'film' registers (Canon EOS, Four Thirds) than the cameras that Angenieux lenses were made for, it is possible for some of you enthusiasts to get hold of some of these legendary 35mm format Angenieux lenses for use on your digital camera, by using an EOS or a 4/3 converter to the specific Angenieux lens mount. Such lenses may be 20 to 50 years old but you will be surprised at the colour (almost 3-D vividness) of these lenses. In knowledgeble markets like Hong Kong such Angenieux second lenses are too expensive (an old P. Angenieux 90mm f/2.5 lens for the Alpa, converted for M42 sells for HK$8,000). I have two of these lens. It is an absolute gem of a lens. It is possible in some markets to get them much cheaper.