Canon bet on the all-electronic EF mount in 1987; it carried 100 million lenses

By the mid-1980s every SLR maker faced autofocus, and the mechanical mounts of the film era were the bottleneck: focus motors and aperture actuation had to thread levers and linkages through the mount. Canon's FD system tied the lens to the body mechanically.

In March 1987 Canon launched the EOS system on the EF (Electro-Focus) mount: a bayonet with the largest diameter in 35mm SLRs, whose only job was to hold the lens and pass electrons through contacts. Every lens carried its own motor. Nothing about the FD mount carried over.

The break was expensive — Canon wrote off its own installed base of FD lenses, even shipping a final FD-mount camera in 1990 to bridge loyalists — but the electronic protocol became a thirty-year platform that rivals adapting their mechanical mounts could not match.

Lens-side electronics let Canon ship industry firsts on the same mount: ring ultrasonic motors, in-lens image stabilization, diffractive optics. EF production passed 80 million lenses in 2012 and 100 million in 2014, and the mount ran until 2018, when Canon's mirrorless RF system inherited the same logic.

Put the motors in the lens; the mount carries only electrons

A motor in each lens beats one compromise motor in every body

Electrons through contacts scale; mechanical linkages do not

The clean break freed the protocol from FD's mechanical legacy

A large mount diameter left headroom for future optics and electronics

A stable protocol let third parties build an ecosystem Canon never had to fund

Interfaces age. When the interface is the constraint, replace it wholesale and keep it stable: one clean break in 1987 bought Canon three decades in which every innovation shipped inside the lens.

EF became the most-produced lens mount in history: 10 million lenses by 1995, 20 million by 2001, 80 million by August 2012 and 100 million by April 2014. Third-party makers reverse-engineered the protocol, RED shipped EF-mount cinema cameras, and mirrorless bodies adapt EF lenses with simple mechanical spacers. Canon's last new EF design shipped in 2018, when the RF system took the same idea further with a wider throat and shorter flange.