This lens replaces the FL58mm f/1.2 (released in March 1964) as a lens representative of Canon’s large-aperture SLR lenses.
The use of large apertures has become the most widespread in standard lenses used as multi-purpose lenses for general shooting such as landscapes, sport, portraits and close-ups. But lenses in the class of a focal ratio of f/1.2 all shared the design problem of eliminating field curvature and flare at maximum aperture. However, as a result of many years of research and development at Canon, this lens shows striking progress in performance at full aperture like the FL50mm f/1.4II (released in May 1968).
The optical system takes the 7-element in 5-group structure and 4 elements using new types of glass are appropriately positioned, sufficiently eliminating high-order spherical aberration and field curvature, while also coming close to completely absorbing the inner reflection that tends to occur in large-aperture lenses.