# Flange focal distance

For an interchangeable lens camera, the flange focal distance (FFD) (also known as the flange-to-film distance, flange focal depth, flange back distance (FBD), flange focal length (FFL), back focus or register, depending on the usage and source) of a lens mount system is the distance from the mounting flange (the interlocking metal rings on the camera and the rear of the lens) to the film or image sensor plane. This value is different for different camera systems. The range of this distance, which will render an image clearly in focus within all focal lengths, is usually measured to a precision of hundredths of millimetres, and is not to be confused with depth of field.
Lenses can be adapted from one mount (and respective FFD) to another. FFD determines whether infinity focus can be accomplished with a simple non-optical adapter. Optics to correct for distance introduce more cost and can lower image quality, so non-optical lens adapters are preferred. A simple non-optical adapter holds the longer FFD lens the appropriate additional distance away from the sensor or film on the shorter FFD camera. A camera body with a shorter FFD can accept a larger number of lenses (those with a longer FFD) by using a simple adapter. A lens with a longer FFD can be more readily adapted to a larger number of camera bodies (those with a shorter FFD). If the difference is small, other factors such as the sizes and positions of the mounting flanges will influence whether a lens can be adapted without optics.

## Standard mounts

Typically, camera bodies with shorter flange focal distance can be adapted more readily to lenses with longer flange focal distance.
| Mount | Flange focal distance | Type | Format | Production | Prime lenses | Zoom lenses | Wide/tele converters | Mount converters | Comments |
| Samsung NX mini | 6.95 mm | Mirrorless | 1" | 2014–2015 | 2 | 1 | | | |
| Pentax Q-mount | 9.2 mm | Mirrorless | 1/2.3" (6.17×4.55 mm) / 1/1.7" | 2011–2019 | 5 | 3 | 0 | 1 | |
| M58×0.75 mm mount | 12 mm | Industrial | 24×36 mm | | | | | | Industrial area and line scan cameras |
| D-mount | 12.29 mm | cine | 8 mm | | | | | | (8 mm movie cameras) |
| CS-mount | 12.526 mm | TV | 1/4", 1/3", 1/2" | | | | | | (surveillance cameras) |
| Nikon Z-mount | 16 mm | Mirrorless | 24×36 mm (FX) | 2018– | 23 | 14 | 2 | 1 | Lens count doesn't include 3rd party products. |
| Nikon Z-mount | 16 mm | Mirrorless | APS-C (DX) | 2018– | 1 | 5 | | 1 | Lens count doesn't include 3rd party products. Can use any of the 24x36 mm (FX) lenses and the FTZ/FTZ II mount adaptor. |
| DJI DL-mount | 16.84 mm | Mirrorless | Super 35 | 2017– | 6 | 1 | | | For use on aerial drone and gimbal cameras. |
| Nikon 1-mount | 17.00 mm | Mirrorless | CX | 2011–2018 | 3 | 8 | | 1 | |
| C-mount | 17.526 mm | cine / TV | 8 mm, 16 mm, 1/3", 1/2", 2/3", 1", 4/3" | ~1926– | | | | | (Bolex, Eclair and Bell & Howell) |
| Fujifilm X-mount | 17.7 mm | Mirrorless | APS-C | 2012– | 23 | 14 | 2 | 1 | |
| Canon EF-M-mount | 18.00 mm | Mirrorless | APS-C | 2012– | 3 | 5 | 0 | 1 | |
| Sony E-mount | 18.00 mm | Mirrorless | APS-C | 2010– | 6 | 14 | 4 | 2 | Lens count doesn't include 3rd party products. All FE lenses (see below) can also be used on APS-C E-mount cameras. |
| Sony E-mount | 18.00 mm | Mirrorless | 24×36 mm (FE) | 2013– | 22 | 17 | 4 | 3 | Lens count doesn't include 3rd party products. |
| Sony FZ-mount | 19.00 mm | cine | Super 35 | 2011– | 0 | 2 | 0 | 3 | |
| Sony FZ-mount | 19.00 mm | cine | 24×36 mm | 2015– | 1 | 2 | | | |
| Micro Four Thirds System | 19.25 mm | Mirrorless | 4/3" | 2008– | 37 | 28 | 1 | 1 | |
| Hasselblad XCD mount | 18.14 mm (+0.05/-0.00) | Mirrorless | Medium Format (127) 43.8×32.9 mm | 2017– | 13 | 1 | | 3 | for Hasselblad X System |
| Canon RF mount | 20.00 mm | Mirrorless | 24×36 mm | 2018– | 12 | 11 | | 3 | |
| L-Mount (Leica, Panasonic Lumix, Sigma, DJI) | 20.00 mm | Mirrorless | 24×36 mm, APS-C | 2014– | 19 | 12 | | | The members of the L-mount alliance are Leica Camera, SIGMA, Panasonic, Ernst Leitz Wetzlar GmbH and DJI |
| LUMIX Panasonic | 20.00 mm | Mirrorless | 24×36 mm, APS-C | 2015– | 8 | 9 | | 7 | L-mount system |
| JVC 1/3" bayonet mount | 25.00 mm | TV | 1/3" 3-CCD (5.24×2.94 mm) | | | | | | |
| Samsung NX-mount | 25.50 mm | Mirrorless | APS-C | 2010–2015 | 8 | 8 | | | |
| Fujifilm G-mount | 26.7 mm | Mirrorless | Medium Format (127) 43.8×32.9 mm | 2017– | 7 | 2 | 1 | | for Fujifilm GFX series cameras |
| Pentax Auto 110 | 27.00 mm | SLR | 13×17 mm | 1978–1985 | 5 | 1 | 0 | 0 | |
| RED ONE interchangeable mount | 27.30 mm | cine | | | | | | | |
| Leica M-mount | 27.8 (inner rails) <-> 27.95 (outer rails) mm | Mirrorless | 24×36 mm | 1954– | | | | | aka Voigtländer VM-mount, Epson EM-mount, Zeiss ZM-mount as well as Konica KM-mount (Hexar RF) and Minolta M-mount (CL/CLE) |
| Nikonos | 28.00 mm | underwater | 24x36 mm | 1963-2001 | 6 | 0 | 0 | 0 | this is the underwater scale focusing camera |
| M39×26tpi mount | 28.80 mm | Mirrorless | 24×36 mm | | | | | | Leica M39×26tpi aka LTM (Leica Thread Mount) aka L39 (not to be confused with M39×1) |
| M39×1/28.8 mount | 28.80 mm | Mirrorless | 24×36 mm | 1948-1978 | | | | | Zorki M39×1/28.8 for Zorki cameras (not to be confused with M39×1 and M39x26tpi) |
| Contax G-mount | 29.00 mm | Mirrorless | 24×36 mm | 1994–2005 | 6 | 1 | 0 | 1 | |
| Olympus PEN F (film) | 28.95 mm | SLR | 18×24 mm | 1963–1972 | 16 | 2 | | | |
| Hasselblad XPan | 34.27 mm | Mirrorless | 24×36 mm & 24×65 mm | 1998–2003 | 3 | 0 | 0 | 0 | Identical to Fujifilm TX series cameras and mount |
| Contax RF-mount | 34.85 mm | Mirrorless | 24×36 mm | | | | | | |
| Nikon S-mount | 34.85 mm | Mirrorless | 24×36 mm | 1947–2005 | | | | | |
| 1/2" TV bayonet mount | 35.74 mm | TV | 1/2" 3-CCD | | | | | | JVC, Hitachi, Panasonic, others, but not Sony |
| Minolta V-mount | 36.00 mm | SLR | APS-H | 1996–1999 | 3 | 5 | 0 | 1 | Vectis S-1, Vectis S-100, Dimâge RD 3000 |
| Sony 1/2" TV bayonet mount | 38.00 mm | TV | 1/2" 3-CCD | | | | | | |
| Olympus Four Thirds System | 38.67 mm | SLR | 4/3" | 2003–2017 | 12 | 30 | 2 | | |
| Aaton mount | 40.00 mm | cine | 16 mm/S16 | | | | | | |
| Panavision SP70-mount | 38.00 mm | cine | | 2018– | | | | | 35 mm & 65 mm |
| Konica F-mount | 40.50 mm | SLR | 24×36 mm | 1960–1965 | 17 | 0 | 0 | 0 | |
| Konica AR-mount | 40.50 mm | SLR | 24×36 mm | 1965–1988 | 36 | 16 | 1 | 0 | |
| Canon FL-mount | 42.00 mm | SLR | 24×36 mm | 1964–1971 | | | | | |
| Canon FD-mount | 42.00 mm | SLR | 24×36 mm | 1971–1990 | 107 | 34 | | | |
| Start (Soviet SLR) | 42.00 mm | SLR | | 1958–1964 | | | | | |
| Minolta SR-mount | 43.50 mm | SLR | 24×36 mm | 1958–2001 | | | | 6 | |
| Fujica X-mount | 43.50 mm | SLR | 24×36 mm | 1980–1985 | | | | | |
| Pentaflex (16 mm cameras) | 44.00 mm | cine | | | | | | | |
| Canon EF-mount | 44.00 mm | SLR | 24×36 mm / APS-H / APS-C | 1987– | 47 | 64 | | | |
| Canon EF-S-mount | 44.00 mm | SLR | APS-C | 2003– | 2 | 9 | 0 | 0 | |
| Praktica B-mount | 44.40 mm | SLR | 24×36 mm | 1978–1990 | | | | | |
| Sigma SA-mount | 44.00 mm | SLR | 24×36 mm / APS-C | 1992– | 14 | 19 | 2 | 4 | |
| M39x1 | 44.00 mm | Mirrorless | 24×36 mm | 1950s | | | | | Braun Paxette rangefinder cameras |
| Arri LPL | 44.00 mm | cine | 25.54x36.70 mm | 2018- | | | | | for Arri Alexa LF |
| Minolta/Konica Minolta/Sony A-mount | 44.50 mm | SLR | 24×36 mm | 1985– | 42+0+17 | 50+2+13 | 6+0+2 | 2+0+0 | |
| Minolta/Konica Minolta/Sony A-mount | 44.50 mm | SLR | APS-C | 2004– | 0+0+3 | 0+3+13 | 0+0+0 | 0+0+0 | |
| Rollei QBM | 44.50 mm | SLR | 24×36 mm | 1970– | | | | | Rollei, Voigtländer |
| Samsung Kenox mount | 44.50 mm | SLR | 24×36 mm | 1997–2002 | 1 | 2 (3?) | 0 | 0 | Although designed in 1990s, mount is manual-focus only; lenses mount and lock on a slightly modified Minolta A-mount adapters |
| Exakta | 44.7 mm | SLR | 24×36 mm | 1936–1969 | | | | | |
| M39x1 | 45.20 mm | SLR | 24×36 mm | 1952–1968 | | | | | Early Russian SLRs (Zenit) (not to be confused with M39×26tpi and M39×1/28,8) |
| M37×1 | 45.46 mm | SLR | 24×36 mm | 1952-1957 | | | | | Asahiflex I, Asahiflex IA (Tower 23), Asahiflex IIB (Tower 23/24), Asahiflex IIA (Tower 22) |
| M42×1 | 45.46 mm | SLR | 24×36 mm | 1949– | | | | | Pentacon, Pentax, Contax S, Praktica, Zeiss ZS, Zenit, many others (not to be confused with T-mount, which is M42×0.75) |
| Pentax K-mount | 45.46 mm | SLR / Mirrorless | 24×36 mm / APS-C | 1975– | 147 | 108 | 8 | 3 | Used also by some Samsung, Ricoh, Chinon, Agfa, Vivitar, Petri and KMZ (Zenit) cameras. Lens count only for Pentax-branded lenses. |
| Contax C/Y-mount | 45.50 mm | SLR | 24×36 mm | 1974–2005 | 24 | 5 | 3 | | Used by some Contax and Yashica SLR cameras |
| Petri Bayonet | 45.50 mm | SLR | 24×36 mm | | | | | | Petri SLRs 1960-77. |
| Mamiya Z | 45.50 mm | SLR | 24×36 mm | 1980– | | | | | |
| Kodak Retina DKL-mount | 45.7 mm | SLR / Mirrorless | 24×36 mm / 28×28 mm | 1958–1977 | 12+6 | 0 | 0 | 0 | DKL variants used by Retina Reflex S (034), Retina Reflex III (041), Retina Reflex IV (051, 051/N), Instamatic Reflex (062), Retina IIIS |
| Voigtländer Bessamatic DKL-mount | 45.7 mm | SLR | 24×36 mm | 1958–1967 | 11+2 | 1 | 0 | 0 | DKL variants used by Bessamatic, Bessamatic deLuxe, Bessamatic m, Bessamatic CS, Ultramatic, Ultramatic CS |
| Braun Paxette Reflex DKL-mount | 45.7 mm | SLR / Mirrorless | 24×36 mm | | | | | | DKL variant used by Paxette Reflex Automatic, Paxette Reflex Automatic II, Tower 33 Reflex, Tower 34 Reflex; Balda Baldamatic III; Witt Iloca Electric / Graflex Graphic 35 Electric; Wirgin Edixa Electronica / Revue Edixa Electronica |
| Voigtländer Vitessa T DKL-mount | 45.7 mm | Mirrorless | 24×36 mm | | 4+? | 0 | 0 | 0 | DKL variant used by Voigtländer Vitessa T; Braun Colorette (Super) II, Colorette (Super) IIB, Colorette (Super) IIL, Colorette (Super) IIBL; Wittnauer Continental, Wittnauer Professional |
| Yashica MA-mount | 45.80 mm | SLR | 24×36 mm | | | | | 1 | (measured); 230AF etc. |
| Olympus OM-mount | 46.00 mm | SLR | 24×36 mm | 1972–2002 | 38 | 14 | | | |
| Nikon F-mount | 46.50 mm | SLR | 24×36 mm / APS-C | 1959– | 213 | 117 | | | Used by some Kiev F-mount cameras. Only Nikon manufactured lenses counted. Nikon claims that there is over 400 Nikkor lens models manufactured. |
| Leica R-mount | 47.00 mm | SLR | 24×36 mm | 1964–2009 | | | | | |
| KMZ Zenit DKL-mount | 47.58 mm | SLR | 24×36 mm | 1964–1968 | 5 | 1 | 0 | 0 | Zenit/Зенит 4/5/6 "Байонет Ц", an unofficial DKL-mount variant |
| B4-mount | 48.00 mm | TV | 2/3" 3-CCD (9.6×5.4 mm) | 1992– | | | | | Mount was in use since at least 1978, wasn't officially standardized until 1992. |
| Contax N | 48.00 mm | SLR | 24×36 mm | 2000–2005 | 4 | 5 | 0 | 1 | |
| Tamron Adaptall/Adaptall-2 | 50.7 mm | SLR | 24×36 mm | 1973-2006 | 14 | 29 | 3 | 26 | No camera uses Adaptall lenses natively, intended to be used with mount adapters. Many lenses have revisions, only original optical formulas are counted. |
| Arri Standard | 52.00 mm | cine | | | | | | | |
| Arri B | 52.00 mm | cine | | | | | | | |
| Arri PL | 52.00 mm | cine | | | | | | | |
| Leica S-mount | 53.00 mm | SLR | 45×30 mm | 1996– | | | | | |
| Mini T-mount | 55.00 mm | SLR | 24×36 mm | 1957–1962 | | | | | Taisei, M37×0.75 |
| T-mount | 55.00 mm | SLR | 24×36 mm | 1962– | | | | | Tamron T-400, M42×0.75 (not to be confused with M42×1) |
| YS mount | 55.00 mm | SLR | 24×36 mm | –1969 | | | | | Sigma, Upsilon, Accura, Polaris, Sun, Aetna, Beroflex, Petri, Raynox, N.P.S., Formula, Dionar, Universal, Soligor, Yashica, Spiratone. M42×0.75 (not to be confused with M42×1) Same as T-mount but with aperture coupling |
| Mamiya 6 | 56.20 mm | Mirrorless | 6×6 cm | 1989–1995 | 3 | 0 | 0 | 0 | Rangefinder camera system, flange focal distance might not be precise. |
| Panavision PV-mount | 57.15 mm | cine | | 1972– | | | | | 35 mm & 16 mm |
| Mamiya 7 | 59.00 mm | Mirrorless | 6×7 cm | 1995–2014 | 6 | 0 | 0 | 0 | Rangefinder camera system |
| OCT-19 | 61.00 mm | cine | | | | | | | |
| Hasselblad H-mount | 61.63 mm | SLR | 6×4.5 cm | 2002– | | | | | for Hasselblad H System |
| Mamiya 645 | 63.30 mm | SLR | 6×4.5 cm | 1975– | | | | | |
| Novoflex [de] A-mount | 63.3 mm | SLR | | | | | | | (measured) "A"-type adapters for follow-focus system |
| Contax 645 | 64.00 mm | SLR | 6×4.5 cm | 1999– | | | | | |
| Zenza Bronica ETR | 69.00 mm | SLR | 6×4.5 cm | 1976–2004 | 17 | 2 | | | |
| Pentax 645 | 70.87 mm | SLR | 6×4.5 cm | 1984– | 25 | 8 | 2 | 2 | |
| Rollei SLX | 74.00 mm | SLR | 6×6 cm | 1976–2005 | | | | | |
| Pentacon Six | 74.1 mm | SLR | 6×6 cm | 1956–1992 | | | | | Used also by Exakta 66 and Kiev 60 series cameras |
| Hasselblad V-mount | 74.90 mm | SLR | 6×6 cm | 1957–2013 | | | | | for Hasselblad V system |
| Kowa Six/Super 66 | 79.00 mm | SLR | 6×6 cm | 1968–1974 | 9 | 0 | | | |
| Hasselblad 1000F & 1600F | 82.10 mm | SLR | 6×6 cm | 1948–1957 | | | | | |
| Salyut/Kiev mount | 82.10 mm | SLR | 6×6 cm | 1972–1980 | | | | | Used by Salyut-S/Салют-C, Zenit/Zenith-80, Kiev 88 cameras |
| Pentax 6×7 | 84.95 mm or 85.00 mm | SLR | 6×7 cm | 1969–1999 | 25 | 2 | 3 | | |
| Zenza Bronica SQ | 85.00 mm | SLR | 6×6 cm | 1980–2003 | 14 | | | | |
| Zenza Bronica GS | 85.00 mm | SLR | 6×7 cm | 1983–2002 | 9 | 0 | 2 | | |
| Zenza Bronica S2A | 101.70 mm | SLR | 6×6 cm | 1959–1980 | | | | | |
| Rollei SL66 | 102.80 mm | SLR | 6×6 cm | 1966–1992 | | | | | |
| Mamiya RZ | 105.00 mm | SLR | 6×7 cm | 1982– | | | | | |
| Mamiya RB | 112.00 mm | SLR | 6×7 cm | 1970– | | | | | |
| Ricoh 126C-Flex | 62.22 mm | SLR | 24×24 mm | 1968-1969 | | | | | |
| 16-SP | 52 mm | Cine | 16 mm | 1965-1991 | | | | | Used on the Soviet Kinor 16 and Krasnogorsk cameras |
| Kiev-16U | 31 mm | Cine | 16 mm | | 3 | | | | Used on the Soviet Kiev-16U camera |
| 1KSR-1M | 57 mm | Cine | 35 mm | | | | | | Used on the Soviet Konvas-1M, 7M, Automat cameras |
| 1KSR-2M | 61 mm | Cine | 35 mm | | | | | | Used on the Soviet Konvas-2M, 8M, Kinor-35 cameras |
| Vivitar TX | 56.25 mm | SLR | 24×36mm | 1976- | 10 | | | 10 | Generic mount used to be attached on many cameras thanks to differents adapters |

## Precision

Flange focal distance is one of the most important variables in a system camera, as lens seating errors of as little as 0.01 mm will manifest themselves critically on the imaging plane and focus will not match the lens marks. Professional movie cameras are rigorously tested by rental houses regularly to ensure the distance is properly calibrated. Any discrepancies between eye focus and measured focus that manifest them­selves across a range of distances within a single lens may be collimation error with the lens, but if such discrepancies occur across several lenses, it is more likely to be the flange focal distance or the ground glass (or both) that are misset.

### Film use

Due to research on optimal flange focal distance settings, it is currently considered better for flange focal distance to be set to somewhere within the film's emulsion layer, rather than on the surface of it. Therefore, the nominal flange focal depth will be equivalent to the distance to the ground glass, whereas the actual flange focal depth to the aperture plate will in fact be ~0.02 mm less.