Talking about the Lens Mount

A lens mount is a metal area that has been machined into a particular shape to fit a specific camera body type. Each camera manufacturer uses a different lens mount design. The lens is attached to the camera at the lens mount ring by lining up a small dot on both the camera body and the lens. The lens is then gently rotated into place. The lens mount also contains electrical contacts that will match up with contacts on the lens ring mount to allow the camera to control the lens.

A Leica R series teleconverter, with the female side of the Leica R bayonet mount. This side is also used on the camera body.
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A lens mount may be a screw-threaded type, a bayonet-type, or a friction lock type. Modern still camera lens mounts are of the bayonet type, because the bayonet mechanism precisely aligns mechanical and electrical features between lens and body. Screw-threaded mounts are fragile and do not align the lens in a reliable rotational position, yet types such as the C-mount interface are still widely in use for other applications like video cameras and optical instrumentation.

Bayonet mounts generally have a number of tabs (often three) around the base of the lens, which fit into appropriately sized recesses in the lens mounting plate on the front of the camera. The tabs are often "keyed" in some way to ensure that the lens is only inserted in one orientation, often by making one tab a different size. Once inserted the lens is fastened by turning it a small amount. It is then locked in place by a spring-loaded pin, which can be operated to remove the lens.

Lens mounts of competing manufacturers (Nikon, Canon, Contax/Yashika, Pentax, etc.) are almost always incompatible. Many allege that this is due to the desire of manufacturers to "lock in" consumers to their brand. However, since there are other differences between manufacturers specifically the flange focal distance from the lens mount to the film or sensor one would not want to mount a lens which wasn't specifically designed for their type of camera, at least not without an adapter to correct the spacing.

In movie cameras, the two most popular mounts in current usage on professional 35 mm cameras are Arri's PL mount and Panavision's PV mount. The Panavision mounts are exclusively used with Panavision lenses, and As a result are only available on Panaflex cameras or third-party cameras "Panavised" by a Panavision rental house, whereas the PL mount style is favored with most other cameras and cine lens manufacturers. Both of these mounts are held in place with locating pins and friction locking rings. Other mounts which are now largely historical or a minority in relation to current practices are listed below.

List of lens mount types

These types are organized by category; find details in the section that follows.


  • Canon EF
  • Canon EF-S
  • Canon FD
  • Canon FL
  • Contax N
  • Contax/Yashica bayonet
  • Four Thirds System
  • Fujica X bayonet
  • Konica original bayonet
  • Konica AR 47mm bayonet
  • Leica M mount
  • Leica R bayonet
  • M42
  • Mamiya bayonet
  • Micro Four Thirds System
  • Minolta AF
  • Minolta V
  • Minolta MD
  • Miranda bayonet (all Miranda cameras had a dual bayonet/M42 screw mount)
  • Nikon F
  • Olympus OM
  • Pentax K
  • Sigma SA
  • T-mount (T-thread)
  • Yashica AF
  • Aaton universal
  • Arri bayonet
  • Arri PL
  • Arri standard
  • B4
  • BNCR
  • C mount
  • CA-1
  • PV (Panavision)


  • C mount
  • CS mount
  • Front-plate mount
  • List of lens mounts

    This list of lens mounts is ordered by flange focal distance, from shortest to longest. It includes both digital, still photography and movie lens mounts.

    focal distance
      D mount 8 mm movie and CCTV 0.625 inch 32 TPI Screw 12.29 mm
      CS mount 16 mm movie and CCTV 1 inch 32 TPI Screw 12.52 mm
      C mount 16 mm movie and CCTV 1 inch 32 TPI Screw 17.526 mm (0.69 inches)
    Canon EX     Camcorder     Bayonet 20 mm
      Micro Four Thirds   digital still ~38mmA   Bayonet ~20 mm
    Bolex   16 mm movie     Breech lock 23.22 mm
    Leica M bayonet   35 mm still 44 mm   Bayonet 27.8 mm
    Canon screw mount   35 mm still M39 1 mm Screw
    Leica M39 screw mount   35 mm still, enlargers M39 26 TPI Screw 28.8 mm
    Narciss   16 mm still M24 1 mm Screw 28.8 mm
    Olympus Pen F   35 mm half-frame still     Bayonet 28.95 mm
    Hasselblad Xpan   35 mm panoramic still     Bayonet 34.27 mm
    Alpa   35 mm still     Bayonet 37.80 mm
    Minolta Vectis   30.2mm 16.7mm APS still     Bayonet 38mm
    Olympus E, Panasonic Lumix DMC-L, Leica Digilux Four Thirds 17.3mm x 12.98mm digital still ~44mmA   Bayonet 38.67 mm
    Aaton universal   16 mm movie     Breech lock 40 mm
    Canon R   35 mm still     Breech lock 42 mm
    Canon FL   35 mm still     Breech lock 42 mm
    Canon FD   35 mm still     Breech lock 42 mm
    Fujica-X   35 mm still     Bayonet 43.5 mm
    Minolta SR/MC/MD   35 mm still     Bayonet 43.5 mm
    Petriflex   35 mm still     Breech lock 43.5 mm
    Canon EF   35 mm still 54mm   Bayonet 44 mm
    Canon EF-S   APS-C digital still 54mm   Bayonet 44 mm
    Sigma SA   35 mm still     Bayonet 44 mm
    Paxette   35 mm still M39 1 mm Screw 44 mm
    Praktica B   35 mm still     Bayonet 44.4 mm
    Minolta AF, Sony Alpha   35 mm still     Bayonet 44.5 mm
    Rolleiflex SL35   35 mm still     Bayonet 44.6 mm
    Exakta, Topcon   35 mm still     Bayonet 44.7 mm
    Pentax K   35 mm still     Bayonet 45.5 mm
    Praktica M42 lens mount 35 mm still 42 mm 1 mm Screw 45.5 mm
    Yashica/Contax   35 mm still     Bayonet 45.5 mm
    Mamiya ZE   35 mm still     Bayonet 45.5 mm
    Olympus OM   35 mm still     Bayonet 46 mm
    Nikon F-mount   35 mm still 44mm   Bayonet 46.5 mm
    Leica R   35 mm still     Bayonet 47 mm
    Contax-N   35 mm still     Bayonet 48 mm
    Praktina   35 mm still     Breech lock 50 mm
    Arri standard   35 mm and 16 mm movie     Tab lock 52 mm
    Arri bayonet   35 mm and 16 mm movie     Bayonet 52 mm
    Arri PL   35 mm and 16 mm movie     Breech lock 52 mm
    Tamron T2, T-mount or T-thread 35 mm still M42 0.75 mm Screw 55 mm
    Panavision PV mount   35 mm movie     Breech lock 57.15 mm
    Mamiya 7/7II   Medium format still     Bayonet ~60 mm ???
    Mitchell BNCR mount   35 mm movie     Breech lock 61.468 mm
    Mamiya 645   Medium format still     Bayonet 63.3 mm
    Leitz Visoflex II/III   35 mm still     Bayonet (Leica M) 68.8 mm
    Pentax 645   Medium format still     Bayonet 70.87 mm
    Arri Maxi PL   70 mm movie 64mm     73.5 mm
    Pentacon Six   Medium format still     Breech lock 74.1 mm
    Hasselblad   Medium format still     Bayonet 74.9 mm
    Kowa Six/Super 66   Medium format still     breech lock 79 mm
    Pentax 6x7   Medium format still     Bayonet 84.95 mm
    Leitz Visoflex I   35 mm still M39 26 TPI Screw 91.3 mm
    Bronica S2A   Medium format still 57 1 Bayonet 101.7 mm
    Rolleiflex SL66   Medium format still     Bayonet 102.8 mm
    Mamiya RZ   Medium format still     Bayonet 105 mm
    Mamiya RB   Medium format still     Bayonet 112 mm


    Column Description
    OEM model line(s) primary manufacturer(s) or model line(s) with this mount
    Interchangeable type name interchangeable mounts used by multiple camera body and lens manufacturers
    Frame size maximum or typical film or image sensor format or size used for this mount
    Camera type digital, still, movie, CCTV, ...
    Throat or thread diameter Nominal inside-female or outside-male major diameter (D) with units: inch, mm, or M (ISO 68-1 metric thread pitch mm)
    Mount thread pitch (P) either: (Unified-thread) pitch count/inch, or (metric) mm/thread pitch
    Mount type Bayonet, Breech, Screw, ...
    Flange focal distance Nominal (mm) distance from film or image sensor to lens mount

    Secondary lens mount

    Secondary lens refers to a multi-element lens mounted either in front of a camera's primary lens, or in between the camera body and the primary lens.

    (D)SLR camera & interchangeable-lens manufacturers offer lens accessories like extension tubes and secondary lenses like teleconverters; which mount in between the camera body and the primary lens, both using and providing a primary lens mount.

    Canon PowerShot A and Canon PowerShot G cameras have a built-in or non-interchangeable primary (zoom) lens; and Canon has "conversion tube" accessories available for some Canon PowerShot camera models which provides either a 52mm or 58mm "accessory/filter" screw thread. Canon's close-up, wide- (WC-DC), and tele-conversion (TC-DC) lenses have 2, 3, and 4-element lenses respectively, so they are multi-element lenses and not diopter "filters". diopters.htm


    ^ A: The authoritative normative source for 4/3 standards information is Four-Thirds.Org and not 3rd-party reviews.

    4/3's published facts:

    • "Size of the 4/3-type Sensor: The standard diagonal length of the sensor is 21.63
    • millimeters (0.852 in). It is half that of 35-mm film format (36 millimeters (1.4 in) x 24
    • millimeters (0.94 in) = 43.27 millimeters (1.704 in)) and suitable format for professional use in digital age. The image circle of the interchangeable lens is specified based on this diagonal length. The focal length is about a half that of a 135 film camera lens assuming the same angle of view."
    • "The foundation for the high picture quality of the Four Thirds system is the lens mount, which is about twice the diameter of the image circle."
    • "Differences between Four Thirds System mount and Micro Four Thirds System mount: Mount diameter reduction; As a result of research aimed at facilitating the design of compact, lightweight lenses while maintaining the current strength, the outer diameter of the lens mount has been reduced by approx. 6
    • millimeters (0.24 in). ... the Micro Four Thirds System ... specifies the optimum flange back length required to reduce camera size and thickness, assuming the omission of the mirror box. The flange back length has been reduced to about 1/2 that of the Four Thirds System."
    • 21.63mm * 2 = 43.26 millimeters (1.703 in) or ~44mm
    • 43.26mm - 6mm = 37.26 millimeters (1.467 in) or ~38mm
    • (21.63mm)^2 = ( ( 17.3mm ^ 2 ) + ( 12.98mm ^ 2 ) ); See: Pythagorean theorem (5^2 = 4^2 + 3^2)
    NOTE: Some published reviews of 4/3 instead cite the (female) "outside diameter" of the lens or mount as ~50mm (and micro-4/3 as ~44mm), and not the appropriate major diameter (D) ~44mm which is the camera body's female mount inside-diameter and the lens's male mount outside-diameter (micro-4/3 ~38mm).