Sony E
FLANGE 18 mm2010–
Fairly compact throat with a ring of ten gold contacts. The most common mirrorless mount you'll meet.
Found on Sony a7 / a9 / FX3 / a6000 series
How to identify
your lens mount
▸ Open the simulator
Found a lens in a drawer and have no idea what it fits? You don't need the model number — the back of the lens tells you almost everything. Here's what to look at, then a rear-view illustration of every mount so you can match yours by eye. We do it for the obscure vintage mounts, so we did it for all of them.
1
Does it screw or click?
A thread that spins in like a jar lid = M42 screw mount. Tabs that lock with a quarter-turn = a bayonet. A chrome collar you rotate while the lens stays still = Canon FD breech-lock.
2
Are there gold contacts?
A ring of gold electrical pins means it's modern (mirrorless or autofocus DSLR). No contacts at all means a vintage manual or classic cinema lens.
3
Is there an aperture ring?
A marked f-stop ring on the barrel points to vintage, cine, or Fuji glass. No aperture ring (aperture set in-camera) points to Canon EF/RF and most mirrorless.
4
How big is the throat?
A very wide opening = full-frame mirrorless or medium format. A small opening = Micro Four Thirds, APS-C, or a rangefinder mount. Throat size narrows it down fast.
Wide throats, a ring of gold electronic contacts, and no aperture ring on the lens (aperture is set in the camera). If your lens has clean gold pins and no manual aperture ring, it's one of these — the brand tells you which.
Canon RF
FLANGE 20 mm2018–
Very wide throat, a dense band of twelve contacts, and a red mounting dot. Larger than the old EF opening.
Found on Canon R5 / R6 / R8 / C70
Nikon Z
FLANGE 16 mm2018–
The widest throat of the big three, with a very short flange — the glass sits almost flush with the contacts.
Found on Nikon Z6 / Z7 / Z8 / Z9
L-Mount
FLANGE 20 mm2015–
Shared by Leica, Panasonic and Sigma. Wide throat, red dot, and a squared contact block — one lens fits all three brands.
Found on Panasonic S / Leica SL / Sigma fp
Fujifilm X
FLANGE 17.7 mm2012–
APS-C, so a medium throat. Many X lenses keep a marked aperture ring — but the gold contacts give away that it's modern.
Found on Fujifilm X-T / X-H / X100 series
Micro Four Thirds
FLANGE 19.25 mm2008–
Notably smaller opening than full-frame mirrorless, with contacts. Shared by Panasonic and Olympus/OM System.
Found on Panasonic GH / OM System / BMPCC 4K
Fujifilm G
FLANGE 26.7 mm2017–
Medium-format mirrorless — an even bigger throat than full frame, with a deep contact band.
Found on Fujifilm GFX 50 / 100 series
Hasselblad XCD
2016–
Big medium-format throat; most XCD lenses hide a leaf shutter, so the barrel is chunky behind the mount.
Found on Hasselblad X1D / X2D / 907X
Longer flange distances (the mirror needs room), so these lenses stick out further from the mount. Modern ones have contacts; older manual ones add an aperture ring.
Canon EF
FLANGE 44 mm1987–
Eight gold contacts, a red dot (and a white square for EF-S), and NO aperture ring — Canon went all-electronic in 1987. The most adapted mount on earth.
Found on Canon 5D / 6D / 7D / Rebel
Nikon F
FLANGE 46.5 mm1959–
The great survivor — unchanged bayonet since 1959. Look for the metering coupling ridge on the aperture ring; older lenses add chrome 'rabbit ear' prongs.
Found on Nikon D850 / D780 / film SLRs
Pentax K
FLANGE 45.5 mm1975–
Pentax's bayonet replacement for the M42 screw. Aperture ring on manual versions; the same basic mount for 50 years.
Found on Pentax K1000 / KX / modern K-1
Big, all-mechanical mounts built for rugged film and digital-cine cameras. No electronics in the classic versions — the lens locks with a rotating collar on the camera, not by twisting the lens.
ARRI PL
FLANGE 52 mm1982–
"Positive Lock." Four flanges and a large 54 mm throat; you twist a ring on the camera to lock it, and the lens never rotates. The film-industry standard.
Found on ARRI / RED / Sony Venice (with adapter)
ARRI LPL
FLANGE 44 mm2018–
Large-format PL. Wider throat and shorter flange than PL, with LDS data contacts — made for full-frame cine sensors.
Found on ARRI Alexa LF / Mini LF / 35
XPL
2010s–
An oversized PL variant for ARRI's 65 mm sensor — the biggest of the family. You'll only see it on rental large-format bodies.
Found on ARRI Alexa 65
B4 (2/3")
FLANGE 48 mm1980s–
Unmistakable: a fat multi-pin connector and often a built-in zoom/focus servo grip. Designed for 2/3-inch broadcast sensors.
Found on Broadcast ENG / studio video lenses
Sony FZ
2011–
Sony's native cine mount. Rare — most shooters run a PL or E adapter on top of it rather than native FZ glass.
Found on Sony PMW-F3 / F5 / F55
This is where the "what mount is my old lens?" question usually lands. None of these have electronic contacts. Every one has an aperture ring. The giveaways are the locking mechanism and a few distinctive details.
M42 screw
FLANGE 45.5 mm1949–1970s
It SCREWS in — no bayonet tabs at all, just a 42 mm thread. If your old lens spins in like a bottle cap, it's M42 (a.k.a. "universal screw"). Often a single aperture pin at the back.
Found on Pentax Spotmatic · Praktica · Zenit · Takumar
Canon FD
FLANGE 42 mm1971–1987
A silver "breech-lock" ring: you twist a chrome collar to mount it while the lens body stays still. Aperture ring has an 'A'/'O' position with a lock. Canon's pre-EF manual mount.
Found on Canon AE-1 · A-1 · F-1
Minolta SR (MC/MD)
FLANGE 43.5 mm1958–2001
Three-claw bayonet with an aperture ring and a small MC/MD coupling tab. The short 43.5 mm flange makes these a favourite to adapt to mirrorless.
Found on Minolta SRT · X-700 · XD-11
Olympus OM
FLANGE 46 mm1972–2002
The tell is the aperture ring sitting right at the FRONT of the barrel near the filter, not by the mount, plus a DOF-preview slider. Compact, beautifully made primes.
Found on Olympus OM-1 · OM-2 · OM-4
Contax / Yashica (C/Y)
FLANGE 45.5 mm1975–2005
Bayonet with an aperture ring; the prize here is the Carl Zeiss glass (Planar, Distagon) marked 'C/Y'. Green/orange focal markings are a hint.
Found on Contax RTS · 139 · Yashica FX
Leica R
FLANGE 47 mm1976–2009
Leica's SLR bayonet — tall, precise, with one to three metering cams stepping down the barrel. Not to be confused with the smaller rangefinder M mount.
Found on Leica R3 · R6 · R8
Konica AR
FLANGE 40.5 mm1965–1987
Bayonet with an aperture ring; the giveaway is the "Hexanon" name and an EE (auto) lock on the aperture ring. The short 40.5 mm flange makes Hexanons superb mirrorless-adapt glass.
Found on Konica Autoreflex T · FT-1 · Hexanon glass
Leica M
FLANGE 27.8 mm1954–
Rangefinder, not SLR — very shallow, with a small silver rangefinder cam follower inside the throat. Tiny, jewel-like lenses with no room for a mirror behind them.
Found on Leica M3 · M6 · M10 · M11
Large, mostly electronic mounts on big digital-back and medium-format bodies. You'll rarely misidentify these — the sheer throat size gives them away.
Hasselblad H
FLANGE 61.6 mm2002–
Huge throat with leaf-shutter lenses and a full contact ring. Built for 645-size digital backs.
Found on Hasselblad H4D / H6D
Phase One XF
2015–
Phase One's pro medium-format mount — big, electronic, leaf-shutter Schneider glass. Studio and landscape territory.
Found on Phase One XF / IQ backs
Mamiya / PhaseOne 645
1999–
The 645 autofocus mount, bridging film Mamiya bodies and early digital backs. Large bayonet, some manual aperture control.
Found on Mamiya 645 AFD · Phase One DF
DL
2016–
A compact electronic medium-format mount seen on Hasselblad's smaller system bodies. Wide throat, full contacts, no aperture ring.
Found on Hasselblad X (via adapter) / compact MF
Identified your lens? Drop it and your camera into the simulator to see the exact field of view — and if the mounts don't match, focalcomp shows which adapter bridges them.
How do I tell if my lens is a screw or bayonet mount?
Try to turn it. If it spins in continuously like a bottle cap, it's a screw mount — almost always M42 (42 mm thread). If it seats with a short quarter-turn and clicks, it's a bayonet. A chrome ring you rotate while the lens body stays still is a Canon FD breech-lock.
My old lens has no electronic contacts — what does that mean?
No gold pins means it's a manual-focus lens: either vintage (M42, Nikon F, Minolta, Olympus OM, Contax/Yashica, Leica) or classic cinema (PL). These set aperture with a physical ring and can be adapted to almost any mirrorless camera with a simple mechanical adapter.
Can I use an old lens on a modern mirrorless camera?
Usually yes. Mirrorless cameras have short flange distances, so a plain adapter can space almost any vintage or DSLR lens correctly. You focus and set aperture manually. focalcomp's registry shows which adapters bridge each mount, and the simulator shows exactly how the lens will frame.
What is flange focal distance and why does it matter?
It's the gap from the mount to the sensor. A lens can be adapted onto any body with a shorter flange distance (you add a spacer). That's why short-flange mirrorless mounts (E, RF, Z, L) accept nearly everything, and why you can't easily go the other way.