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What is Flange Focal Distance? Lengths for Lens Mounts

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The Flange Focal Distance is the distance from the mounting flange to the image sensor in a camera, and it determines the compatibility of different lenses with different cameras, with a lens's flange distance needing to be longer than a camera's for successful adaptation without additional modifications or optics.

The Flange Focal Distance is the space between a camera lens mount and the film plane or image sensor.

The short distance on mirrorless cameras is why it is easy to adapt film lenses to those mounts. Space taken up by the mirror is replaced with a lens adapter.

Flange distance is also referred to as:

  • flange focal depth
  • flange back distance
  • flange focal length
  • back focus
  • flange-to-film distance
  • register

Film Plane Indicator / Focal Plane Mark

Film Plane Indicator on a Canon AE-1
Film Plane Indicator on a Canon AE-1

Each manufacturer uses a different mark to show the film or sensor plane location. The most common symbol is a circle with a line through it.

For Canon 35mm film cameras, such as the Canon AE-1, the mark is to the left of the prism. The distance from that mark to the front of the lens mark represents the flange focal distance.

Focal Plane Mark on a Nikon D750 DSLR
Focal Plane Mark on a Nikon D750

Example shown on a Nikon D750 DSLR. The digital camera obviously doesn’t use film, so Nikon referrers to it as the focal plane mark.

Flange Distance as Shown on a Minolta SRT-101
The Distance Between the Red and Blue Lines is the Flange Distance

The flange distance is what will determine if a lens can be adapted to a camera body. The flange distance of the lens needs to be larger than the camera it will be used on.

Mounting a lens further away than it was designed is possible. There are M42 (45.46mm) to Nikon F-mount (46.50mm) adapters. The added space acts like a short extension tube. The lens will not be able to focus to infinity.

Avoid adapters that use a correcting lens element. The cheap optics will degrade the lens’s image quality.

Different camera systems have different standard flange focal distances. Mirrorless cameras can all use lenses designed for DSLRs and film SLR cameras.

Lenses designed for manual focus 35mm film cameras are popular to adapt. They have physical aperture rings. The adapters are simple because no connections are needed between a lens and the camera body.

For instance, it is possible to mount M42 screw mount lenses on Pentax K mount bodies by using an adapter.

“Smart adapters” have electrical contacts for control over auto focus and aperture. Compatibility will vary between different systems.

An example is using a Canon EOS lens on a Micro Four Thirds camera body.

Minolta Auto Bellows Rokkor X 100mm f/4 Lens
Minolta Auto Bellows Rokkor X 100mm f/4 Lens

There are some lens adapters that do not include optics to correct for infinity focus. These are for mounts with a longer flange distance than the design for the adapted lens.

A good example is a Minolta MD-mount to Nikon F-mount.

These can be useful for macro photography for attaching a lens onto a bellows. In my instance I wanted to attach a Minolta bellows lens onto a Nikon PB-4 bellows.

Mount Flange Focal Distance Type Format
Samsung NX mini 6.95 mm Mirrorless 1"
Pentax Q-mount 9.2 mm Mirrorless 1/2.3"
M58×0.75 mm mount 12 mm Industrial 24×36 mm
D-mount 12.29 mm cine 8 mm
CS-mount 12.526 mm TV 1/4", 1/3", 1/2"
Nikon Z-mount 16 mm Mirrorless 24×36 mm
DJI DL-mount 16.84 mm Mirrorless Super 35
Nikon 1-mount 17.00 mm Mirrorless CX
C-mount 17.526 mm cine / TV 8 mm, 16 mm, 1/3", 1/2", 2/3", 1", 4/3"
Fujifilm X-mount 17.7 mm Mirrorless APS-C
Canon EF-M mount 18.00 mm Mirrorless APS-C
Sony E-mount 18.00 mm Mirrorless APS-C & Full Frame
24×36 mm (FE) - - -
Sony FZ-mount 19.00 mm cine Super 35
Micro Four Thirds System 19.25 mm Mirrorless 4/3"
Hasselblad XCD mount 18.14 mm Mirrorless Medium Format (127) 43.8×32.9 mm
Canon RF mount 20.00 mm Mirrorless 24×36 mm
Leica L-Mount (formerly CL-mount) 20.00 mm Mirrorless 24×36 mm, APS-C
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
Fujifilm G-mount 26.7 mm Mirrorless Medium Format (127) 43.8×32.9 mm
Pentax Auto 110 27.00 mm SLR 13×17 mm
RED ONE interchangeable mount 27.30 mm cine -
Leica M-mount 27.80 mm Mirrorless 24×36 mm
Nikonos 28.00 mm underwater 24x36 mm
M39 lens mount (M39x26tpi mount) 28.80 mm Mirrorless 24×36 mm
M39 lens mount (M39×1/28.8 mount) 28.80 mm Mirrorless 24×36 mm
Contax G-mount 29.00 mm Mirrorless 24×36 mm
Olympus PEN F (film) 28.95 mm SLR 18×24 mm
Hasselblad XPan 34.27 mm Mirrorless 24×36 mm & 24×65mm
Contax RF-mount 34.85 mm Mirrorless 24×36 mm
Nikon S-mount 34.85 mm Mirrorless 24×36 mm
1/2" TV bayonet mount 35.74 mm TV 1/2" 3-CCD
Minolta V-mount 36.00 mm SLR APS-H
Sony 1/2" TV bayonet mount 38.00 mm TV 1/2" 3-CCD
Olympus Four Thirds System 38.67 mm SLR 4/3"
Aaton mount 40.00 mm cine 16mm/S16
Panavision SP70 mount 38.00 mm cine -
Konica F-mount 40.50 mm SLR 24×36 mm
Konica AR-mount 40.50 mm SLR 24×36 mm
Canon FL-mount 42.00 mm SLR 24×36 mm
Canon FD-mount 42.00 mm SLR 24×36 mm
Start (Soviet camera) 42.00 mm SLR
Minolta SR-mount 43.50 mm SLR 24×36 mm
Fujica X-mount 43.50 mm SLR 24×36 mm
Pentaflex (16 mm cameras) 44.00 mm cine
Canon EF-mount 44.00 mm SLR 24×36 mm
Canon EF-S-mount 44.00 mm SLR APS-C
Praktica B-mount 44.40 mm SLR 24×36 mm
Sigma SA-mount 44.00 mm SLR 24×36 mm
Arri LPL 44.00 mm cine 25.54x36.70 mm
Minolta/Konica Minolta/Sony A-mount 44.50 mm SLR 24×36 mm
Minolta/Konica Minolta/Sony A-mount (APS-C) 44.50 mm SLR APS-C
Rollei QBM 44.50 mm SLR 24×36 mm
Samsung Kenox mount 44.50 mm SLR 24×36 mm
Exakta 44.7 mm SLR 24×36 mm
M39x1 45.20 mm SLR 24×36 mm
M37×1 45.46 mm SLR 24×36 mm
M42×1 45.46 mm SLR 24×36 mm
Pentax K-mount 45.46 mm SLR 24×36 mm
Contax/Yashica (C/Y)-mount 45.50 mm SLR 24×36 mm
Petri Bayonet 45.50 mm SLR 24×36 mm
Mamiya Z 45.50 mm SLR 24×36 mm
Kodak Retina DKL-mount 45.7 mm SLR 24×36 mm / 28×28 mm
Voigtländer Bessamatic DKL-mount 45.7 mm SLR 24×36 mm
Braun Paxette Reflex DKL-mount 45.7 mm SLR / Mirrorless 24×36 mm
Voigtländer Vitessa T DKL-mount 45.7 mm Mirrorless 24×36 mm
Yashica MA-mount 45.80 mm SLR 24×36 mm
Olympus OM-mount 46.00 mm SLR 24×36 mm
Nikon F-mount 46.50 mm SLR 24×36 mm / APS-C
Leica R-mount 47.00 mm SLR 24×36 mm
KMZ Zenit DKL-mount 47.58 mm SLR 24×36 mm
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
Tamron Adaptall/Adaptall-2 50.7 mm SLR 24×36 mm
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
T-mount 55.00 mm SLR 24×36 mm
YS mount 55.00 mm SLR 24×36 mm
Mamiya 6 56.20 mm Mirrorless 6×6 cm
Panavision PV-mount 57.15 mm cine
Mamiya 7 59.00 mm Mirrorless 6×7 cm
OCT-19 61.00 mm cine
Hasselblad H-mount 61.63 mm SLR 6×4.5 cm
Mamiya 645 63.30 mm SLR 6×4.5 cm
Novoflex A-mount 63.3 mm SLR
Contax 645 64.00 mm SLR 6×4.5 cm
Zenza Bronica ETR 69.00 mm SLR 6×4.5 cm
Pentax 645 70.87 mm SLR 6×4.5 cm
Rollei SLX 74.00 mm SLR 6×6 cm
Pentacon Six 74.1 mm SLR 6×6 cm
Hasselblad V-mount 74.90 mm SLR 6×6 cm
Kowa Six/Super 66 79.00 mm SLR 6×6 cm
Hasselblad 1000F & 1600F 82.10 mm SLR 6×6 cm
Salyut/Kiev mount 82.10 mm SLR 6×6 cm
Pentax 6×7 84.95 mm or 85.00 mm SLR 6×7 cm
Zenza Bronica SQ 85.00 mm SLR 6×6 cm
Zenza Bronica GS 85.00 mm SLR 6×7 cm
Zenza Bronica S2A 101.70 mm SLR 6×6 cm
Rollei SL66 102.80 mm SLR 6×6 cm
Mamiya RZ 105.00 mm SLR 6×7 cm
Mamiya RB 112.00 mm SLR 6×7 cm
Updated on 2023-07-18
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