Quick-release lens mount — twist 90° and lock solid. Canon EF, Nikon F, Sony E standard. Beats screw threads for speed on set.
On set, you need quick changes — and that's exactly what the bayonet mount was developed for. Instead of screwing a lens into the threads for minutes, you push the lens in, turn it 90 degrees, and it's rock solid. The mechanical lock is achieved via two or three pins in the camera's bayonet ring, which engage with corresponding grooves on the lens mount. It's precise work — with poor manufacturing, the whole thing rattles; with good manufacturing, it fits like a glove.
Canon, with its EF mount, long set the standard, Nikon with its F mount — both systems are incompatible, even though the outer diameter looks similar. This is a classic design decision: bayonet mounts are proprietary. Sony E is slimmer and allows for more compact cameras because the flange distance (distance from sensor to mount) is shorter. On average, you notice the difference in handling: you change three lenses in five minutes instead of fifteen — this saves time on shooting locations with tight schedules.
Practically, you need to be mindful of dirt when attaching a new lens. Dust in the bayonet mount leads to image defects, scratches on the mount pins to electrical failures when it comes to autofocus contacts. Some cameras have small protective caps for the body mount — use them. A broken pin cannot be easily repaired and renders the entire camera unusable. Also important: do not turn the lens beyond its natural resistance. It should click into place, not crack.
The electronic interface in a modern bayonet mount not only transmits focus signals but also data such as focal length, aperture, and lens profiles — essential for in-camera corrections and metadata in post-production. Older manual lenses with bayonet mounts still work, but without this information. Those who work a lot with legacy glass need to keep this in mind during color grading.