- Flange focal distance — the gap between the mount and the sensor — decides what can adapt to what
- A shallow mount can adapt deep-mount lenses; going the other way needs corrective glass and costs image quality
- PL is the long-standing cinema standard; LPL is the shallower large-format successor
- Adapters can pass electronics or nothing at all, and a cheap one that shifts back focus will make sharp lenses look soft
A mount is a mechanical interface and a distance measurement. Get the distance wrong by a fraction of a millimetre and nothing in the frame reaches focus properly.
Flange Focal Distance Is the Whole Story
Every mount specifies exactly how far the sensor sits behind the lens flange. A lens is designed to focus at that distance, and an adapter is really just a spacer that makes up the difference. This is why adapting works in one direction only: you can put a deep-mount lens on a shallow-mount body, because the adapter adds the missing distance, but you cannot shorten a mount that is already too deep without adding optical elements. Mirrorless bodies have very shallow flange distances, which is exactly why they adapt almost anything.
PL and LPL
PL has been the cinema standard for decades, with a 54mm flange distance and a locking collar that clamps heavy glass securely. The entire rental ecosystem — primes, zooms, matte boxes, support — grew up around it. LPL is the newer, shallower, wider-throat mount built for large-format sensors and the lenses that cover them. Because LPL is shallower than PL, a PL-to-LPL adapter is a simple mechanical spacer and PL glass works on LPL bodies. The reverse is not possible, so LPL lenses stay on LPL cameras.
EF, E, RF, L, Z and MFT
EF remains common on lower-budget cinema bodies because the used lens market is enormous and cheap, and because the mount is deep enough to adapt from. Sony E, Canon RF, the L-mount alliance, Nikon Z and Micro Four Thirds are all shallow mirrorless mounts, which makes them adaptation hubs: EF, PL, Nikon F, and vintage still glass all reach them with a simple mechanical adapter. Some cinema cameras ship with a user-swappable mount, which is the cleanest solution of all — change the mount rather than stack an adapter in front of the sensor.
Active vs Passive Adapters
A passive adapter is metal and nothing else. It fits manual lenses perfectly and is the right choice for PL glass, which has no electronics. An active adapter carries contacts that pass aperture control, autofocus, image stabilisation and lens metadata through to the body. Active adapters are convenient but introduce a compatibility matrix — firmware, third-party lenses, and specific camera models all have quirks — and the more electronics in the chain, the more there is to fail on a shoot day.
Speed Boosters and Focal Reducers
A focal reducer, commonly sold as a speed booster, sits inside the adapter and compresses the lens image circle onto a smaller sensor. The effect is a wider field of view and roughly a stop of extra light, which is genuinely useful for putting full-frame glass on a Super 35 or Micro Four Thirds body. The trade is that you have added optical elements to a lens that was not designed for them, so corner sharpness and contrast can suffer. Good ones are expensive for a reason.
Back Focus and Shimming
Even a correct mount can drift. If lenses will not hit infinity, or if sharpness varies across a set, back focus is the usual culprit — the flange distance has moved by fractions of a millimetre through wear, impact or a loose mount. Rental houses check and shim collimation as routine maintenance. If you own a camera and adapt regularly, having back focus checked is worth doing before any job that matters, because no amount of careful focus pulling fixes a mount sitting at the wrong depth.
Where This Connects
For the deeper walkthrough of every cinema mount and which cameras use them, read Cinematography Lens Mounts Explained. The optical side of the lenses themselves is in Cinema Lenses and Anamorphic Lenses, sensor sizes and coverage are covered in Cinema Cameras, and the stills perspective is in Lenses.