The making of the Retrofocus Pierre Angénieux offered photographers and filmmakers new optical possibilities in 1950 with the Retrofocus. The invention arose out of the simple fact that the moving mirror system of the new reflex cameras made it impossible for photographers to use lenses with a focal length of less than 40mm. Pierre Angénieux worked initially on improvements to the viewfinders of reflex cameras, for which he applied for several patents between 1943 and 1950. His invention of the Retrofocus, a telephoto configuration leaving sufficient room behind the last lens, then made it possible to use a wideangle lens on a reflex camera. This major innovation lay at the origin of the universal development of 24×36 SLR (Single Lens Reflex) camera with interchangeable lenses. The R1, the very first Angénieux Retrofocus lens, was a 35mm with an aperture of f/2.5, a world record at the time. First presented to the public at the 21st Salon de la Photographie et du Cinéma in Paris, it was ideal for reflex cameras but also aroused the interest of owners of 24×36 rangefinders by virtue of its remarkable brightness. More than 50,000 units were sold. It was followed in 1953 by the 28mm f/3.5 Retrofocus, a wide-angle lens opening the field of view up to 75°, and in 1957 by a 24mm f/3.5 reaching 83°. While SOM-Berthiot, the other French manufacturer in the market of 24×36 prime lenses, took great pride in offering an exhaustive range, Angénieux concentrated on the bestselling lenses, which explains its lesser presence in the sector of longer focal lenght.

The Challenge of the Zoom A zoom must be calculated so that all the rays of light emitted from a point of the object to be filmed will converge, regardless of the number of lens elements to be passed through, on a single point to obtain a sharply defined image with the minimum of optical defects. As is known, however, rays of light differ in terms of their point of impact and incidence on a lens, their color, the shape of the lens, and quality of the glass. It is only the rays very close to the optical axis that preserve their direction. Away from this axis, the light is scattered. The calculation must therefore follow the trajectory of each ray of light and simulate its passage through a lens as to obtain the right optical combination (succession of lens elements) in compliance with the given constraints as regards technical specifications, cost, size, and weight. All of Pierre Angénieux’s genius lay in developing a system of calculations involving only the rays essential to the formation of an image and thus reducing the time required to calculate a lens by ninety percent. He considered only the rays in a cross-sectional plane of the lens, 10–20 rays per lens, no more, on the optical axis in the center of the image for three colors and three different apertures and then two or three points of the image in the field and always in this meridian plane. Intuition and experience play a key part in the selection of rays and appraisal of the final image. If the image was no good in the end, it was necessary to revise the choice of optical combination by adding a lens element or changing its shape and so on. Each new study considered acceptable involved the creation of a prototype to assess optical and mechanical performance and decide on modifications wherever necessary.

Pierre Angénieux’s greatest innovation remains the creation and industrial production of the first zoom with mechanical compensation, which was to revolutionize practice in television, cinema, and photography. The first prototype was a 4x zoom for 16mm cameras presented in 1956 and brought into production in 1957, initially for Bell & Howell 16mm cameras for amateurs. This zoom replaced the turret with its three lenses of fixed focal length. This surpassed the zooms with optical compensation in power and performance, especially the Pan Cinor of SOM-Berthiot developed by Roger Cuvillier. Pierre Angénieux gave his lens a new dimension, namely the ability to vary the magnification of the image with a device of limited size and no impairment of focus during change in focal length, a great challenge regarded as impossible by German optical engineers. The list of requirements was fully met by the F=17-68 f/2.2, the first Angénieux zoom, deliveries of which began in 1958. Over 70,000 of these lenses were sold on the market between 1957 and the end of the 1970s. This new zoom technology of the late 1950s was a major event for the movie industry heralding the end of turret cameras and the widespread use of reflex viewfinding. Pierre Angénieux registered Zoom as a brand name in France, after which the word entered the French language. While the Angénieux range featured just one zoom among a multitude of fixed focal lengths in 1958, the only fixed focal length to survive in 2001 was the super 5.9mm wide-angle for 16mm film cameras.