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), 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 known as the depth of focus (not to be confused with the similarly named depth of field).

Diagram illustrating the flange focal length of an SLR–type and a mirrorless–type camera

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 higher FFD lens the appropriate additional distance away from the sensor or film on the lower FFD camera. A camera body with a lower FFD can accept a larger number of lenses (those with a higher FFD) by using a simple adapter. A lens with a higher FFD can be more readily adapted to a larger number of camera bodies (those with a lower 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[1]	Mirrorless	1/2.3" (6.17×4.55 mm) / 1/1.7"	2011–	5	3	0	1
D-mount	12.29 mm	cine	8 mm						(8 mm movie cameras)
CS-mount	12.526 mm[2][3][4]	TV	1/4", 1/3", 1/2"						(surveillance cameras)
Nikon Z-mount	16 mm	Mirrorless	24×36 mm	2018–	5	3		1
Nikon Z-mount	16 mm	Mirrorless	APS-C (DX)	2019-		2			Can use any of the 24x36 mm lenses and the FTZ mount adaptor.
DJI DL-mount	16.84[5]	Mirrorless	Super 35	2017–	4	0
Nikon 1-mount	17 mm[6]	Mirrorless	CX	2011–				1
C-mount	17.526 mm[7]	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–	12	11	2	1[8]
Canon EF-M-mount	18 mm	Mirrorless	APS-C	2012–	3	5	0	1
Sony E-mount	18 mm	Mirrorless	APS-C	2010–	6	11	4	2
Sony E-mount	18 mm	Mirrorless	24×36 mm (FE)	2013–	11	13	4	2
Sony FZ-mount	19 mm	cine	Super 35	2011–	0	2	0	3
Sony FZ-mount	19 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–	8			1	for Hasselblad#XCD-System
Canon RF mount	20 mm	Mirrorless	24×36 mm	2018–	2	2		3
Leica L-Mount (formerly CL-mount)	20 mm	Mirrorless	24×36 mm, APS-C	2014–	3	3
JVC 1/3" bayonet mount	25 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
Pentax Auto 110	27 mm	SLR	13×17 mm	1978–1985	5	1	0	0
RED ONE interchangeable mount	27.30 mm	cine
Leica M-mount	27.80 mm[8]	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 mm[9]	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 L39 (not to be confused with M39×1)
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
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 mm	TV	1/2" 3-CCD
Olympus Four Thirds System	38.67 mm	SLR	4/3"	2003–2017	12	30	2
Aaton mount	40 mm	cine	16mm/S16
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
Pentaflex (16 mm cameras)	44 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
Sigma SA-mount	44.00 mm	SLR	24×36 mm / APS-C	1992–				0
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
QBM	44.5 mm[10]	SLR	24×36 mm						Rollei, Voigtländer
Exakta	44.7 mm[11]	SLR	24×36 mm	1936–1969
M39x1	45.2 mm[12]	SLR	24×36 mm	1952–1968					Early Russian SLRs (Zenit) (not to be confused with M39×26tpi and M39×1/28,8)
M42×1	45.46 mm	SLR	24×36 mm	1949–					Pentacon, Pentax, Contax S, Praktica, Zeiss ZS, Zenit (not to be confused with T-mount, which is M42×0.75)
Pentax K-mount	45.46 mm	SLR / Mirrorless	24×36 mm	1975–	141[13]	105	8	3	lens count only for Pentax-branded lenses
Contax C/Y-mount	45.50 mm	SLR	24×36 mm	1974–2005	24	5	3
Petri Bayonet	45.50 mm	SLR	24×36 mm
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	45.8 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			Only Nikon manufactured lenses counted. Nikon claims that there is over 400 Nikkor lens models manufactured. [14]
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)
Contax N-mount	48.00 mm	SLR	24×36 mm	2000–2005	4	5	0	1
Arri STD	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
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
Panavision PV-mount	57.15 mm	cine		1972–					35 mm & 16mm
OCT-19	61.00 mm	cine
Mamiya 645	63.30 mm	SLR	6×4.5 cm
Novoflex A-mount	63.3 mm	SLR							(measured) "A"-type adapters for follow-focus system
Contax 645	64.00 mm	SLR	6×4.5 cm
Pentax 645	70.87 mm	SLR	6×4.5 cm	1984–
Rollei SLX	74.00 mm	SLR	6×6 cm	–2005
Pentacon Six	74.1 mm	SLR	6×6 cm	1956–1992
Hasselblad 2000 & 500	74.90 mm	SLR							Hasselblad V mount
Hasselblad 1000F & 1600F	82.10 mm	SLR
Pentax 6×7	84.95 mm or 85.00 mm	SLR	6×7 cm	1969–1999
Rollei SL66	102.80 mm	SLR	6×6 cm
Mamiya RZ67	105 mm	SLR	6×7 cm
Mamiya RB67	111 mm	SLR	6×7 cm

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 groundglass (or both) that are misset.

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 groundglass, whereas the actual flange focal depth to the aperture plate will in fact be ~0.02 mm less.

References

Archived 2012-03-19 at the Wayback Machine pentax.jp
Hornberg, Alexander (2007-02-27). Handbook of Machine Vision. John Wiley & Sons. ISBN 9783527610143.
"CS-Mount | Edmund Optics". www.edmundoptics.com. Retrieved 2018-07-28.
"Flangeback Distances | Universe Optics". Universe Optics. Retrieved 2018-07-28.
https://www.dpreview.com/news/2095513456/dji-launches-zenmuse-x7-super-35mm-camera-module-with-raw-video-capture
http://www.ikegami.com/cb/products/pdf/tech/lensmount.pdf
http://photo.net/nikon-camera-forum/00Zu0J
Bertram Hönlinger, Carl Zeiss AG (2014): All Zeiss QBM lenses were designed for 44.5 mm. The 44.7 mm value found on some US sites is wrong.
Wrotniak, J. Andrzej
Zenit's mount history: M39x1/45,2
Pentax Lens Search | PentaxForums.com
Nikon F-Mount, nikonusa.com

Markerink, Willem-Jan. Camera Mounts & Registers. Retrieved on November 6, 2005.

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.

[1] Archived 2012-03-19 at the Wayback Machine pentax.jp

[2] Hornberg, Alexander (2007-02-27). Handbook of Machine Vision. John Wiley & Sons. ISBN 9783527610143.

[3] "CS-Mount | Edmund Optics". www.edmundoptics.com. Retrieved 2018-07-28.

[4] "Flangeback Distances | Universe Optics". Universe Optics. Retrieved 2018-07-28.

[5] ttps://www.dpreview.com/news/2095513456/dji-launches-zenmuse-x7-super-35mm-camera-module-with-raw-video-capture

[ikegami.com-7] ttp://www.ikegami.com/cb/products/pdf/tech/lensmount.pdf

[9] ttp://photo.net/nikon-camera-forum/00Zu0J

[10] Bertram Hönlinger, Carl Zeiss AG (2014): All Zeiss QBM lenses were designed for 44.5 mm. The 44.7 mm value found on some US sites is wrong.

[11] Wrotniak, J. Andrzej

[12] Zenit's mount history: M39x1/45,2

[13] Pentax Lens Search | PentaxForums.com

[14] Nikon F-Mount, nikonusa.com

Flange focal distance

Standard mounts

See also

References