A lens mount is an interface — mechanical and often also electrical — between a photographic camera body and a lens. It is confined to cameras where the body allows interchangeable lenses, most usually the rangefinder camera, single lens reflex type or any movie camera of 16 mm or higher gauge. Lens mounts are also used to connect optical components in instrumentation that may not involve a camera, such as the modular components used in optical laboratory prototyping which join via C-mount or T-mount elements.
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/Yashica, Pentax, etc.) are almost always incompatible. In addition to the mechanical and electrical interface variations, the flange focal distance from the lens mount to the film or sensor can also be different. Many allege that these incompatibilities are due to the desire of manufacturers to "lock in" consumers to their brand.
In movie cameras, the two most popular mounts in current usage on professional digital cinematography cameras are Arri's PL-mount and Panavision's PV-mount. The PL-Mount is used both on Arri and R.E.D. digital cinematography cameras, which are in 2012 the most used cameras for films shot in digital. The Panavision mounts are exclusively used with Panavision lenses, and thus 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.
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.
|OEM model line(s)||Interchangeable type name||Frame size||Camera type||Throat or thread diameter||Mount thread pitch||Mount type||Flange focal distance|
|M6x0.35 to M12x0.5 "board camera" mount||1/6 inch to 1 inch||Security IP Cameras, Automotive Backup cameras, Webcams, Digital Image scanners||6mm to 12mm||0.35 to 0.5 mm pitch||Screw||No Flange. Back focal distance from <1mm to 12mm.|
|Pentax Q||Pentax Q||1/2.3 inch||digital still||Bayonet||9.2 mm|
|D-mount||8 mm||movie, CCTV||15.88 mm (0.625 inch)||32 TPI||Screw||12.29 mm|
|CS-mount||1/3 inch, 1/2 inch||movie, CCTV, industrial, scientific||25.40 mm (1 inch)||32 TPI||Screw||12.52 mm|
|C-mount||16 mm, 2/3 inch, 1 inch1/2 inch,||movie, CCTV, industrial, scientific||25.40 mm (1 inch)||32 TPI||Screw||17.526 mm (0.69 inches)|
|Nikon 1 series||Nikon 1 mount||13.2 x 8.8mm||digital still||Bayonet||17 mm|
|Fujifilm X-Pro1||Fujifilm X-mount||APS-C||digital still||Bayonet||17.7 mm|
|Canon EOS M||Canon EF-M mount||APS-C||digital still, movie||58 mm (Outer)||Bayonet||18 mm|
|Sony Alpha NEX||Sony E-mount||35 mm and 23.4 mm × 15.6 mm APS-C||digital still, movie||46.1 mm (1.815 inch)||Bayonet||18 mm|
|Olympus Pen & OM-D series; Panasonic G, GF, GX & GH Series||Micro Four Thirds||17.3 mm × 12.98 mm||digital still, camcorder||A[›]~38 mm||Bayonet||19.25 mm|
|Canon EX||camcorder||Bayonet||20 mm|
|Bolex||16 mm||movie||Breech lock||23.22 mm|
|Samsung NX||NX-mount||APS-C23.4 mm × 15.6 mm||digital still||42 mm||Bayonet||25.5 mm|
|Pentax Auto 110||110 film||still||Bayonet||27 mm|
|Minolta/Leica M bayonet||M-mount (aka EM, VM, ZM)||35 mm||still||44 mm||Bayonet||27.80 mm|
|Leitz/Minolta CL, Minolta CLE||compact M-mount||35 mm||still||44 mm||Bayonet||27.80 mm|
|Konica Hexar RF||KM-mount||35 mm||still||44 mm||Bayonet||28 mm (27.80 mm?)|
|Canon screw mount||35 mm||still||M39||1 mm||Screw|
|Leica M39 screw mount||M39 (aka L-Mount, LSM)||35 mm||still, enlargers||M39||26 TPI||Screw||28.80 mm|
|Narciss||16 mm||still||M24||1 mm||Screw||28.8 mm|
|Olympus Pen-F||35 mm half-frame||still||Bayonet||28.95 mm|
|Contax/ (Kiev rf) I, II, III, IIa, IIIa||35 mm||still||Double bayonet||34.85 mm|
|Contax G||35 mm||still||Breech lock||29.00 mm|
|Hasselblad Xpan||35 mm panoramic||still||Bayonet||34.27 mm|
|Nikon Rangefinder||Nikon S-mount||35 mm||still||Bayonet||34.85 mm|
|Alpa||35 mm||still||Bayonet||37.80 mm|
|Minolta Vectis||V-mount||APS[disambiguation needed]30.2 mm × 16.7 mm||still||Bayonet||36.00 mm (38 mm?)|
|Olympus E, Panasonic Lumix DMC-L, Leica Digilux||Four Thirds||17.3 mm × 12.98 mm||digital still||A[›]~44 mm||Bayonet||38.67 mm|
|Aaton universal||16 mm||movie||Breech lock||40 mm|
|Konica F||Konica F-mount||35 mm||still||40 mm||Bayonet||40.50 mm|
|Konica A/R||AR-mount||35 mm||still||47 mm||Bayonet||40.50 mm (40.7 mm)|
|Miranda Camera Company||Miranda bayonet/M44||35 mm and APS-C||still, industrial||Bayonet||41.5 mm|
|Canon R||35 mm||still||Breech lock||42 mm|
|Canon FL||35 mm||still||Breech lock||42 mm|
|Canon FD||FD-mount||35 mm||still||Breech lock||42.00 mm|
|Fujica-X||Fujica X-mount||35 mm||still||49 mm||Bayonet||43.5 mm|
|Minolta SR/MC/MD||SR-mount||35 mm||still, medical||Bayonet (54°)||43.50 mm|
|Petriflex||35 mm||still||Breech lock||43.5 mm|
|Mamiya/Sekor E||35 mm||still||Bayonet||43.5 mm|
|Canon EOS||EF mount (aka ZE)||35 mm||still, movie||54 mm||Bayonet||44.00 mm|
|Canon EOS||EF-S mount||APS-C||digital still||54 mm||Bayonet||44.00 mm|
|Sigma SA||35 mm||still||Bayonet||44.00 mm|
|Paxette||35 mm||still||M39||1 mm||Screw||44 mm|
|Praktica B||35 mm||still||Bayonet||44.40 mm|
|(Konica) Minolta AF/Alpha/Dynax/Maxxum, Sony Alpha DSLR/SLT||A-mount (aka ZA)||35 mm and APS-C||still, industrial||49.7 mm (1.939 inch)||Bayonet (54°)||44.50 mm|
|Rolleiflex SL35||35 mm||still||Bayonet||44.46 mm|
|Exakta, Topcon||35 mm||still||Bayonet||44.7 mm|
|Zenit 39mm||Zenit M39||35 mm||still||M39||1 mm||Screw||45.2 mm|
|Pentax K||K-mount (aka ZK)||35 mm||still||Bayonet||45.46 mm|
|Asahiflex||35 mm||still||37 mm||1 mm||Screw||45.46 mm|
|Praktica||M42 lens mount||35 mm||still||42 mm||1 mm||Screw||45.46 mm|
|Yashica/Contax||Y/C-mount||35 mm||still||Bayonet||45.5 mm|
|Mamiya ZE||35 mm||still||Bayonet||45.5 mm|
|Kyocera Yashica 230 AF etc.||MA-mount||35 mm||still||Bayonet||~45.8 mm|
|Olympus OM||OM-mount||35 mm||still||46 mm||Bayonet||46 mm|
|Nikon F-mount||Nikon F-mount||35 mm||still, industrial||44 mm||Bayonet||46.5 mm|
|Leica R||R-mount||35 mm||still||Bayonet||47.00 mm|
|Contax-N||35 mm||still||Bayonet||48 mm|
|Praktina||35 mm||still||Breech lock||50 mm|
|Tamron||T-Thread (Very earliest type)||35 mm||still||M37||0.75mm||Screw||50 mm|
|Tamron||Adapt-A-Matic||35 mm||still||Bayonet||50.7 mm|
|Tamron||Adaptall 1 & 2||35 mm||still||Bayonet||50.7 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, industrial||42 mm||0.75 mm||Screw||55 mm|
|Sigma Corporation||YS Auto T-Thread||35 mm||still||42 mm||0.75 mm||Screw||55 mm|
|Tokina||T-thread type||35 mm||still||47 mm||0.75 mm||Screw||55 mm|
|Sony Mavica||Mavica||digital still||Bayonet||57 mm|
|Panavision PV mount||35 mm||movie||Breech lock||57.15 mm|
|Mamiya 7/7II||6×7||still||Bayonet||60 mm (approx.)|
|Mitchell BNCR mount||35 mm||movie||Breech lock||61.468 mm|
|Mamiya 645||6×4.5||still||Bayonet||63.3 mm|
|Zeiss Panflex 5522/23 for Contax rf||35 mm||still||Double bayonet||64.50 mm|
|Leitz Visoflex II/III||35 mm||still||Bayonet (Leica M)||68.8 mm|
|Pentax 645||6×4.5||still||Bayonet||70.87 mm|
|Arri Maxi PL||70 mm||movie||64 mm||73.5 mm|
|Pentacon Six||6×6||still||Breech lock||74.1 mm|
|Kowa Six/Super 66||6×6||still||breech lock||79 mm|
|Pentax 6x7||6×7||still||Bayonet||84.95 mm|
|Leitz Visoflex I||35 mm||still||M39||26 TPI||Screw||91.3 mm|
|Bronica S2A||6×6||still||57 mm||1||Bayonet||101.7 mm|
|Rolleiflex SL66||6×6||still||Bayonet||102.8 mm|
|Mamiya RZ67||6×7||still||Bayonet||105 mm|
|Mamiya RB67||6×7||still||Bayonet||112 mm|
|Canon RC-701||Canon SV||digital still||Bayonet||2/3 inch|
|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 format or image sensor size used for this mount|
|Camera type||still, digital still, movie, cinema, 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|
Focusing lens mount 
So some manufacturers (e.g. Linhof) offered special focusing lens mounts, so-called wide-angle focusing accessories for their cameras. With such a device, the lens could be focused precisely without moving the entire front standard.
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. Various lensmakers also offer optical accessories that mount in front of the lens; these may include wide-angle, telephoto, fisheye, and close-up or macro adapters.
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 provide 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".
^ 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 millimetres (0.852 in). It is half that of 35-mm film format (36 millimetres (1.4 in) x 24 millimetres (0.94 in) = 43.27 millimetres (1.704 in)) 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 millimetres (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 millimetres (1.703 in) or ~44mm
- 43.26mm - 6mm = 37.26 millimetres (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).
See also 
- "S Mount Movie Lenses (Cine-Kodak Special II Camera & Others)". Jimscamerasseattle.com. Retrieved 2013-04-22.
- "Camera Story - 1987-1991 EOS". Canon. Retrieved 2008-07-22.
- Digital Compact Cameras - RC-701 SLR Type Still Video Camera, Canon Camera Museum
- "About Four Thirds, Standard, Whitepaper (Summary of Standard)". Four Thirds System. Retrieved 2008-08-11.
- "About Four Thirds, Standard, Benefits of Four Thirds". Four Thirds System. Retrieved 2008-08-11.
- "Micro Four Thirds, Standard, Whitepaper (Summary of Standard)". Four Thirds System. Retrieved 2008-08-11.
- "Olympus and Panasonic announce Micro Four Thirds". Digital Photography Review.
General references 
- Markerink, Willem-Jan. "Camera mounts & registers".
- SLR Mount Identification Guide
- Standard: GOST 10332-72 (in Russian) — M42×1/45.5, M39×1/28.8
- Standard: GOST 10332-63 (in Russian) — M39×1/45.2 (aka «Z39»), M39×1/28.8, bayonet «C» (cameras: «Zenit-5», «Zenit-6», «Zenit-7»), bayonet «Zenit-7» NB 7/12/2012 Site closed see www.zenit-foto.ru (in Russian)
- Camera mounts & registers from Robert Monahan Medium Format Photography Megasite http://medfmt.8k.com/
- Camera mounts & registers from Willem-Jan Markerink http://www.markerink.org/WJM/HTML/mounts.htm
- Camera Mounts Sorted by Register
- Alphabetical List of Camera Mounts
- Nikon Lens Nomenclature - a study in frustration
- Mechanical & Optical Instruments
- DPReview Hands-on preview of Fujifilm X-Pro1
- DPreview Hands-on preview of Canon EOS M