Pentax K-mount

The K- bayonet lens mount is a camera brand Pentax SLR. It was introduced in 1975 as a successor to the M42 screw thread which used Pentax since 1957 in the Asahi Pentax and all subsequent models including the Spotmatic. The back focal length of 45.46 mm was maintained. Pentax has introduced the original K -mount with the introduction of the first three K- cameras: KM, KX and K2. The lens mount has evolved several times and is used in a modified form even in the digital SLR Pentax and Samsung.


The K- bayonet was proposed by Pentax as an open standard for SLR cameras, which is why it is also found in a number of different brands and manufacturers, such as Zenit, Revueflex (brand Quelle GmbH ) or Ricoh (which in October 2011 took over the division of the brand Pentax Photo of the Hoya Group). From 2005 to 2008, finally, Samsung offered with his camera models GX -1S, GX -1L, GX -10 and GX- 20 digital SLR cameras with K bayonet to where it * is to slightly modified versions of the Pentax models DS2, * ist DL2, K10D and K20D acted. As a result, however, Samsung decided to also develop their own bayonet system, which in 2010 placed on the market and no longer compatible with the K bayonet NX bayonet.

Pentax has a high degree of compatibility between lenses and cameras of different generations ensured. As a result, you can - with limitations - also use more than 30 -year-old K -mount lenses with a modern AF body or a DSLR, and vice versa, it is also many modern lenses on an old Pentax K2 use by 1975. Due to the identical back focus many M42 and T-2 lenses can be used with an adapter ring on a camera with K bayonet. Pentax also offers adapters to connect lenses of medium format systems 645 and 67 on cameras with K bayonet on.

The various versions of the K bayonet ( such as K, KA, KAF, see below ) are only mechanically fully compatible with each other, they differ in a row with the modified time details. So light up many newer lenses Series SMC -DA and SMC -DA * not from the full image circle of a small camera as they are provided from the outset only for DSLRs with smaller image sensor. In addition lenses allow the Series SMC -FA -J, SMC -DA and SMC -DA * which have no aperture ring, no manual aperture control required for older cameras. Conversely, with old lenses (up to about 1982), the aperture rings no A- position offered ( for automatic transmission), use only limited exposure programs newer cameras.

The aligned for compatibility policy is also reflected in the fact that with the introduction of lenses with ultrasonic motor ( since 2007 ) both cameras as well as on most lenses, a double focus drive is installed, it allows new lenses with older cameras and Collaborate new cameras with old lenses.

Variant of the K- bayonet


  • Since 1975: "K" - in SMC / SMC - M lenses Original version with mechanical aperture coupling (aperture simulation and automatic diaphragm ).
  • Since 1983: " KA" - in SMC-A lenses "A " position on the aperture ring with locking facility. Six electrical contacts on the bayonet of the camera body keys from electrically conducting or insulating surfaces on the lens and the " A" -position pin. The contacts transferred to a 5-bit code, the smallest aperture (16, 22, 32 or 45) and the number of steps by which the aperture can be opened (giving both the aperture value ) and allow aperture priority and programmed auto and matrix metering. The sixth contact indicates the "A " position camera series. A and P.
  • Since 1987: " KAF " - in SMC -F lenses Similar to the KA- bayonet, but with additional mechanical coupling for the internal camera auto-focus motor and a further electrical contact for serial transmission of information from the lens to the camera body. Introduced for SF series, is also found in the first MZ models.
  • Since 1991: " KAF2 " - for SMC -FA lenses The second generation of autofocus -capable K- bayonet allows the transmission of MTF values ​​from the lens and has two electrical contacts for Power Zoom Lenses certain; for the PZ models and later MZ models (MZ -S, MZ -3, MZ- 5, etc. )
  • Since 1997: " KA2 " How KAF, but without autofocus function specifically for the MZ-M/ZX-M models
  • Since 1997: " KAF " version without mechanical aperture simulator Used in models MZ-30/ZX-30, MZ-50/ZX-50, MZ-60/ZX-60 which is * / * ist D series and the K100D/K110D.
  • Since 2006: " KAF2 " version without mechanical aperture simulator Originally built for driving power zoom lenses contacts are now to control the SDM autofocus drive ( SDM: Supersonic Drive Motor and Super Dynamic motor, ultrasonic motor ) used new lenses. Used in all DSLRs since K10D K100D Super and. The K10D can optionally control the SDM autofocus or power zoom.
  • Since 2008: " KAF3 " (previously only on the objective side ) Lenses with integrated SDM drive, without mechanical AF coupling to the camera body. These lenses can be manually focused camera models that have come on the market before the fall of 2006, work otherwise as KAF2. With cameras there is the name KAF3 not, because until 2013 Pentax has released no housing, lack analogous to the KAF3 lenses, the AF motor in the housing in which.


The original Pentax - K bayonet has two mechanical interfaces between the camera and lens: the driver for the aperture simulator that transmits the set on the lens aperture to the camera and the aperture lever is switched to that between working aperture and open aperture. On the removed lens aperture closes by spring force directly to the value set on the aperture ring can be opened via the diaphragm lever, however. The lens is attached to a camera body, a lever is operated in the camera body to the shutter arm so that the iris is opened fully. Only during the exposure - coupled to the mechanics of the mirror - shows the camera the aperture lever and free the aperture is closed by spring force on the set value. The driver for the aperture simulator rotates a circular potentiometer, the resistance of the meter purports to change the aperture.

The P- KA- bayonet has in addition to the six described above electrical contacts yet another non-obvious change: the displacement of the diaphragm lever is proportional to the area of the aperture so the light value, rather than proportional to the diameter of the aperture. Otherwise, the function is identical to the PK bayonet and so on older cameras fully compatible.

Thus, a camera body with shutter priority over the displacement of the diaphragm lever control the aperture -free, provided the aperture ring in position A ( smallest aperture and A contact closed).

Development since 1997

1997 was introduced with the MZ-50/ZX-50 also a simplified version of the previous autofocus bayonet. This lacks the electrical contacts for the power zoom function and the mechanical scanning of the lens pre-selected aperture value. The aperture can therefore not be set on the lens itself in automatic mode, but only via a rotary knob on the camera. Thus, automatic exposure controls can no longer use with lenses that have an aperture ring without A -position.

These restrictions also apply to the built from 2003 film based camera * is the DSLRs and the * ist D series as well as K100D/K110D. For the exposure to the traditional use of the aperture ring a workaround was at the Pentax DSLRs introduced: In M mode (manual setting ) is dimmed automatically just by pressing a button, measure the exposure and set which matches the preselected aperture exposure time (auto working aperture ). The use of the aperture ring must first be enabled for the camera menu.

To match the cameras without a mechanical aperture scanning published from 2003 to the SMC -FA -J series first lenses without aperture ring. The starting in 2004 built Lenses Series SMC -D FA will continue to have an aperture ring, are for use on DSLRs optimized ( like the letter "D " in both names) and highlight how all existing lenses, the image circle of miniature cameras from. The also sold from 2004 Lens Series SMC -DA is also " digitally optimized " has no aperture ring and is corrected for the smaller image circle of DSLRs with APS-C image sensor format.

In 2006 came with the K10D the first Pentax camera on the market that is capable of lenses with ultrasonic focusing ( for Pentax called SDM) to drive. For this purpose, the power zoom contacts of KAF2 bayonet were integrated into the bayonet again, the support for this model either Powerzoom or SDM lenses. As more cameras, the K100D Super, K20D, K200D and all later models were given the ability to SDM focusing with appropriate lenses. In this case, all the cameras also retain the autofocus motor in the body and can also focus older AF lenses automatically that do not have their own motor.

The first lenses with SDM - drive are standard SMC -DA * and have a dual focus drive, so they can be focused on older, non- SDM -enabled cameras via the housing-side AF motor. As the DA series they have no aperture ring. In summer 2008, Pentax smc PENTAX - introduced with the DA 17 -70mm F4 AL [ IF] SDM a first lens on the market which can be automatically focuses exclusively on SDM drive. On older cameras like the K100D (not Super) and * ist DL this lens can be focused manually.

Ricoh R- K bayonet

The RK mount is a variation of the Pentax K bayonet that was used by the company Ricoh and similar to the KA mount enables iris control from the camera. It differs from the Pentax version by a spring loaded pin in the lens mount, which in newer Pentax cameras can hook into the recess for the AF - spindle in the camera's bayonet mount and prevents the removal of the lens. The Ricoh pin also called pin should be removed before mounting the lens on a modern Pentax camera. This does not apply to all Ricoh lenses, but only for those with an A- position corresponding aperture ring setting that were designed for camera-side aperture control.

Sigma SA bayonet

Hybrid between K and Canon EOS bayonet. EOS contacts and - flange focal length of 44.0 mm instead of 45.46 mm. Mechanically identical to the K- bayonet, but rotated 90 ° clockwise. K- lenses fit on Sigma SD cameras, if the incoming project into the camera parts such as automatic diaphragm lever are mounted out. Thanks to the lower by 1.5 mm flange focal length of SA to K K lenses focus beyond infinity then, but shall, in most cases not sensitive to UV - IR dust protection filter the Sigma SD cameras. If this is the case, can be inserted between the lens and bayonet basically a spacer made of eg 1.5 mm entkupfertem -FR- PCB material. For fixed focal length is often a easy way to set the new stop of the focus ring. For zoom lenses, this second option is valid only if it can be dispensed with synchronization between focusing and zooming, ie refocusing when zooming is accepted.

Summary Table

The following table shows the compatibility of Pentax K lenses with the corresponding cameras. The cameras are analog or digital differed only in the bayonet and, bearing in mind that not all listed cameras always really support all possible with the bayonet exposure measurements ( eg, M, Av ) also. The Pentax ME -F is not considered as a special case.


  • M - manual exposure with Metered
  • M - manual exposure with auto working aperture, no Metered
  • Av - Aperture Priority
  • Av0 - Automatic timer with open aperture
  • P - Program AE
  • AF - Autofocus with rod engine
  • PZ - Power Zoom ( K10D only with severely impaired function)
  • SDM / DCM - Auto focus with ultrasound or DC motor ( K10D with firmware 1.3)
  • X - not useful useful because smallest aperture is always set
  • 1 - image circle is not sufficient or edges with aberrations
  • 2 - The K10D can be changed by a software update PowerZoom operating on SDM operation.


  • On cameras with the KAF/KAF2-Bajonett without aperture simulator, the aperture is set on the camera side rotary wheel at Av Metering.