An Overview of The Pentax K-Mount: History & Compatibility

The Pentax K-mount, also referred to as the “PK-mount” has been around since 1975. It is a bayonet lens mount that was originally designed for 35mm film SLR cameras. (Single-lens reflex)

The mount is still being used by Pentax for their DSLRs. This can lead to compatibility problems as there have been significant modifications to the mount to allow for autofocus and electronic controls.

As cameras added features and technology, lenses and the camera mount needed to be modified. Early autofocus systems and electrical contacts are the easiest differences to see.

  • A three tab bayonet connection launched with K series cameras.
  • Mechanical linkage to communicate aperture for open-aperture metering.
  • Supported by K series, M series (except ME F), and LX cameras.
  • Pentax’s first attempt at an autofocus system.
  • Only one camera and one lens used this mount: Pentax ME F and SMC Pentax-AF 35-70/2.8.
  • Adds aperture priority mode.
  • Introduced in 1983 and supported by A-series and P-series bodies.
  • An attempt at adding auto-focus to lenses.
  • Introduced a small drive shaft to the KA-mount. (Similar to Nikon F-mount lenses of the time.)
  • Added electrical contacts for digital communication with a camera body. Removes the physical linkage used to set maximum aperture information.
  • Bodies lose open-aperture metering and will need to use stop-down metering on pre-A lenses. This is done by pressing the green button.
  • A variation by Ricoh for Rikenon P lenses. It supports Ricoh’s implementation of shutter priority and auto exposure metering modes.
SMC Pentax-M 50mm f/2 Lens for the K-mount
SMC Pentax-M 50mm f/2 Rear Lens Mount

The Pentax K-mount is a bayonet style lens mount with 3 tabs for mounting. Originally designed to be used on 35mm SLRs. It is similar in appearance to the Nikon F-mount and Minolta MD-mount.

Later versions of the lens mount had electrical contacts and a drive shaft for autofocus added. The drive shaft would connect to an autofocus motor inside a camera body.

The flange focal distance is 45.46 mm. This is the same distance as the M42 mount. This was done so that Pentax M42 lenses, used on cameras like the Spotmatic, could be used on K-mount cameras with a lens adapter.

However, due to the relatively large flange distance for a 35mm SLR camera, Pentax K-mount lenses cannot be easily adapted to other SLR or DSLR cameras. There are K-mount lens adapters for all mirrorless camera mounts.

Mirrorless cameras are ideal as autofocus and electronic features will not work. The adapted lens will have to be used in manual mode or aperture priority. If the lens doesn’t have a physical aperture ring, you will not be able to change the aperture.

There are some adapters that have glass optics to allow for focus to infinity. The optics are to compensate for the lens being further away from the imaging plane than it was designed for. Unfortunately, the optics are of poor quality, which greatly reduces image quality.

  • K2 (1975–1980)
  • K2 DMD (1976–1980)
  • KX (1975–1977)
  • KM (1975–1977)
  • K1000 (1976–1997)
  • ME (1976–1980)
  • MX (1976–1985)
  • ME Super (1979–1984)
  • MV (1979–1982)
  • MV1 (1979-1982)
  • ME F (1981–1988)
  • MG (1982–1985)
  • LX (1980–2001)
  • Super A / Super PROGRAM (1983–1987)
  • Program A / Program PLUS (1984–1988)
  • A3/A3000 (1985–1987)
  • P5/P50 (1986–1989)
  • P3/P30 (1985–1988)
  • P3n/P30n (1988–1990)
  • P30t (1990–1997)
  • SFX/SF1 (1987–1989)
  • SFXn/SF1n (1989–1993)
  • SF7/SF10 (1988–1993)
  • Z-10 (1991)
  • Z-1 (flagship model) (1991)
  • Z-20 (1992)
  • Z-50 (1992)
  • Z-1P (flagship model) (1994)
  • Z-5P (1994)
  • Z-70 (1995)
Pentax ZX-50 35mm Film SLR
Pentax ZX-50 35mm Film SLR
  • MZ-S (Flagship model)
  • MZ-3
  • MZ-5 MZ-5n
  • MZ-10
  • MZ-7
  • MZ-6/ZX-L
  • MZ-M
  • MZ50
  • MZ30
  • MZ60
  • *ist (2003–2006)
Pentax 100D DSLR with SMC Pentax-DA f/4-5.6 55-200mm Zoom Lens
Pentax 100D with SMC Pentax-DA f/4-5.6 55-200mm Zoom Lens
  • *ist D Flagship model (2003–2006)
  • *ist DS (2004–2005)
  • *ist DS2 (2005–2006)
  • *ist DL (2005–2006)
  • *ist DL2 (2006)
  • Pentax K100D (2006–2007)
  • Pentax K110D (2006–2007)
  • Pentax K10D (2006–2008)
  • Pentax K10D Grand Prix (limited edition) (2007)
  • Pentax K100D Super (2007–2008)
  • Pentax K200D (2008–2009)
  • Pentax K20D (2008–2009)
  • Pentax K-m (Pentax K2000 in U.S.) (2008–2009)
  • Pentax K-7 (2009–2010)
  • Pentax K-x (2009–2011)
  • Pentax K-r (2010–2012)
  • Pentax K-5 (2010–2012)
  • Pentax K-01 (2012–2013)
  • Pentax K-30 (2012–2013)
  • Pentax K-5 II (2012–2014)
  • Pentax K-5 IIs (2012–2014)
  • Pentax K-50 (2013–2016)
  • Pentax K-500 (2013–2014)
  • Pentax K-3 (2013–2015)
  • Pentax K-S1 (2014–2016)
  • Pentax K-S2 (2015–present)
  • Pentax K-3 II (2015–2018)
  • Pentax K-1 (2016–2018)
  • Pentax K-70 (2016–2022)
  • Pentax KP (2017–2021)
  • Pentax K-1 II (2018–present)
  • Pentax K-3 III (2021–present)
  • Pentax KF (2022–present)

Numerous cameras have utilized the K-mount over the years. Some notable ones include:

CE-4 CE-4s CA-4
CA-4s CM-4 CM-4s
CE-5 CG-5 CM-5
CP-5 CP5s
CP-7m CM-7
C1 C1s CE-4
CE-4s CE-5 CS-2
CS-3 CT-1A CT-1G
CT-4 CT-7 CT-9
CT-10 CT-20
HS-1 HS-2 HS-4
HS-10 HS-40 KE 5
MS-1 MS-2 Super MS-3
Porst Compact Reflex OC Porst Compact Reflex OCN
KR-5 KR-5 Super KR-5 Super II
KR-5 III KR-10 KR-10 Super
KR-10M KR-30sp XR-1
XR-1s XR-2 XR-2s
XR-500 XR500 auto XR-6
XR-7 XR-10 XR-P
XR-20sp XR-Solar XR-M
KS-1000 (Ricoh XR-1) KS-500 (Ricoh XR-500) KS Auto (Ricoh XR-2S)
KS-1 KS-2 (Ricoh XR-7) KSX (Ricoh KR-10)
KSX-P (Chinon CP-5) KS Super KS Super II
V635 V4000 V3800N
V3000N V3000s V2000
XV1 (rebadged Cosina CT-1) XV20 (rebadged Cosina CT-20)

There had to be a better solution than what’s below. You shouldn’t have to start a research project to figure out the compatibility of a lens and camera combination.

This is not a customer friendly process. I am sure this is one of the reasons that has contributed to Pentax having a small share of the camera market.

Table of K-Mount Lens Variations:

Series Prime Lenses Zoom Lenses
K series 34 7
M series 22 8
A series 19 11
F series 7 10
FA series 12 17
D FA series 3 5
DA series 4 18
DA Limited 10 1
DA* series 3 4
  • The first generation of Pentax K-mount lenses.
  • Not officially referred to as K series lenses but are often designated as such to distinguish them from later K-mount lenses.
  • Exclusively manual focus lenses with no electronic features.
  • Name starts with either upper case “SMC” or lower case “smc”, representing the Super-Multi-Coated lens coating.
  • Followed the K series lenses.
  • Manual K-mount lenses without electronic features.
  • Generally smaller in size to match compact camera bodies like the Pentax MX and Pentax ME Super.
  • Introduced “automatic” aperture settings.
  • Had an aperture ring but also an “A” mode, allowing the camera to control the aperture automatically.
  • First autofocus lenses for Pentax.
  • Screw-drive type autofocus.
  • Featured an aperture ring for manual control.
  • Designed for full-frame film SLR cameras.
  • Screw-drive type autofocus.
  • Introduces power zoom lenses.
  • No aperture ring.
  • Coated for digital cameras but also support older 35mm camera formats.
  • Some are weather resistant.
  • Some lenses have aperture rings and others don’t.
  • Designed for Pentax digital cameras with an APS-C digital sensor.
  • No aperture ring.
  • Lighter and cheaper versions of DA series zoom lenses.
  • No aperture ring.
  • Higher quality optics and better weather sealing.
  • No aperture ring.
  • High-quality prime lenses with metal housing.
  • Compact in design.
  • No aperture ring.

Some notable third party K-mount lenses include:

  • Access: 28 mm f2.8 P-MC Macro, 75–300 mm f5.6 PMC Zoom.
  • Angenieux: 70–210 mm f3.5.
  • Agfa: Agfa Color 50 mm f1.4.
  • Arsat: PCS Arsat 35 mm f2.8 Shift Lens.
  • Carl Zeiss Jena: 20 mm f4, 28 mm f2.8, 70–210 mm f4.5, 75–300 mm f4.5-5.6 ED IF MC Macro.
  • Carl Zeiss: Introduced a line of lenses for the K-mount in 2008.