B4-mount

[1] This standard defines the physical mount, but also optical properties and some electrical connections.

[2] The BTA was formed by Japanese broadcaster NHK and included members from Canon, Fuji, Hitachi, Ikegami, JVC, Matsushita (Panasonic), Nikon, Sony and Toshiba.

[3][4] The flange of the mount defines the positioning of the lens relative to the image sensor.

The standard defines that a prism splits the light to form separate images planes for the colours red, green and blue.

Nowadays, cameras with the same mount capture HD with 16:9 aspect ratio, or even 4K video, thanks to improved lenses.