This is a lens aimed at improving the performance of the FL300mm f/2.8 S.S.C. large-aperture telephoto lens, which was released in February 1974, using fluorite that is popular among demanding professional users including press photographers, while also offering full-aperture metering and automatic diaphragm control.

Together with this lens the FD 2x Extender was also developed, and when used with the extender the FD300mm f/2.8 S.S.C. Fluorite Lens can also fully exhibit the functions and performance of a FD600mm f/5.6 S.S.C. Fluorite Lens.

Despite being a large aperture telephoto lens with a brightness of f/2.8, the combination of a fluorite lens element and optical glass elements keeps chromatic aberration extremely small, offering high-resolution and high-contrast definition even at maximum aperture, while also achieving light and smooth focusing through the adoption of a new bearing method for the helicoid.

Furthermore, automatic diaphragm control of a large aperture telephoto lens, which was previously considered to be difficult due to the time lag from the diaphragm blades, has been achieved through the development of a new diaphragm unit, improving operability as a new type of zoom lens.