Pentax K mount
From Wikipedia, the free encyclopedia
The Pentax K mount, sometimes referred to as the "PK mount", is a lens mount standard for mounting interchangeable photographic lenses to 35 mm single-lens reflex (SLR) cameras. It was created by Pentax in 1975,[1] and has been used by all 35 mm and digital Pentax SLRs since. A number of other manufacturers have also produced many K-mount lenses and K-mount cameras.
Contents |
[edit] Mounts
The Pentax K mount has undergone a number of evolutions over the years as new functionality has been added. In general, the term K mount may refer to the original K mount, or to all its variations.
[edit] K mount
The original K mount is a simple bayonet connection with three tabs. It was introduced with the K series of cameras. The lens is locked into the camera with an approx. 70° clockwise turn (when looking at the front of the camera).
The only linkage with the camera is mechanical and involves the aperture. A slot between two of the bayonet tabs on the lens allows the stop-down coupler from the camera to sense the aperture setting on the lens and adjust the light meter display accordingly. Opposite this is the diaphragm release from the lens which extends into the camera body and holds open the spring loaded diaphragm of the lens. When setting up a shot this keeps the diaphragm fully open. When the shutter is released, so is this lever. It allows the diaphragm to close to the desired setting while the film is being exposed, and opens it again after the shutter closes.
Both of these linkages are of course arranged so that they are aligned and spring-loaded by the act of inserting the lens and turning it until it locks.
Bodies equipped with the original K mount include the K series, the M series except the ME F, and the LX. Lenses that support it include those labelled 'SMC Pentax' and 'SMC Pentax-M'. These K mount bodies cannot use lenses that lack an aperture ring, such as FAJ, DA or D-FA.
K-mount lenses can be used on all Pentax bodies, but can only be used in stopped down mode with "crippled" KAF mount bodies (see below).
[edit] KF mount
The KF mount was Pentax's first attempt at an autofocus system. This autofocus system used sensors in the camera body and a motor in the lens. The two were connected via five new electrical contacts on the bayonet mount itself. One permitted the lens to turn on the camera's metering and focus sensors, two focused the lens (towards and away from infinity) and two appear to have been unused and may have been reserved for future functionality.
The KF mount was largely a failure. Only one camera and one lens ever used this mount, the Pentax ME F and SMC Pentax-AF 35-70/2.8. The lens was somewhat large and cumbersome[1] since it had to enclose both the focusing motor (with gears) and batteries to power it. KF and the ME-F are similar in many ways to the system used by Canon in the ill fated Canon T80, introduced several years later.
The ME F can use all Pentax K-mount lenses except for FAJ lenses, which lack an aperture ring. The 35-70 mm lens can be used on all other Pentax K-mount bodies in manual focus mode, but it must be used stopped down on "crippled" KAF bodies.
[edit] KA mount
The KA mount is derived from the original K mount. It allows the lens' aperture to be set by the body, and thus permits shutter priority and program auto exposure modes. It was introduced in 1983, and is supported by A-series and P-series bodies; Pentax lenses that support it are marked 'SMC Pentax-A'. It is completely backward-compatible with the original K mount.
The aperture on the lens is set from the body by the same stop-down lever found on the original K mount, but on KA lenses this lever is proportional to the area of the aperture opening, rather than the diameter as on previous lenses. This allows the body to easily set a specific aperture, since the relationship to F stops is linear. The lenses add an 'A' setting on the aperture dial, which gives the body control of the aperture. Other, numeric settings are used for manual aperture modes—aperture priority and full manual mode.
Six electrical contacts are added to the bayonet ring. One is slightly recessed and allows the lens to indicate whether the aperture ring is set at 'A' or not. If it is, a pin on the lens extends slightly and makes contact, while if the lens is at any other setting the pin is retracted and does not make contact. The other five contacts are used to encode the lens' aperture range. Each contact on the lens is either conducting or non-conducting, providing a binary 1 or 0, respectively. Two contacts encode the lens' minimum aperture—f/16, f/22, f/32 or f/45; although no Pentax K-mount lens has ever had an f/16 minimum aperture, OEM lenses often have. The other three contacts encode the lens' maximum aperture; their meaning is dependent on the minimum aperture indicated by the lens.
[edit] KAF mount
The KAF mount was Pentax's second and much improved attempt at adding auto-focus to lenses. It adds a small drive shaft to the KA mount, allowing the body to adjust the focus of the lens. This makes the lenses less bulky than the earlier KF mount, which had both a motor and batteries inside the lens.
It also adds a seventh electrical contact, this one carrying digital information from the lens to the camera. It carries the following information: focal length, distance to the subject, exact absolute f-stop value, and lens size. This information is used to make better exposure decisions, along with the multi-segmented metering that was introduced in cameras using the KAF mount.
[edit] KAF2 mount
.jpg/180px-K-mount-late-(Pentax-MZ3).jpg)
The KAF2 mount is the same as the KAF mount except that it adds two extra contacts to the inside of the mounting ring for power zooming, and transmits modulation transfer function (MTF) data through the digital seventh contact. On the K10D digital SLR model the two power contacts can also power Supersonic Direct Drive lenses.
[edit] KA2 mount
The KA2 is identical to KAF, but lacks the autofocus drive shaft. Another way of looking at it is that it adds the seventh contact for digital information to the KA mount.
[edit] "Crippled" KAF mount
The "crippled" KAF mount is used on the MZ-30/ZX-30, MZ-50/ZX-50, MZ-60/ZX-60, the *ist series and the K100D/K110D. The only difference between the regular KAF mount and the crippled version is the removal of the mechanical stop-down coupler/indicator. The result is that most of these bodies can only correctly use lenses which have an "A" setting on the aperture ring or "crippled" KAF lenses. With a K/M (also known as "pre-A") lens, the body cannot tell what aperture the lens is set to with the "crippled" mount. The *ist series and K series digital cameras have a work-around which allows K/M lenses to be used in full manual exposure mode by simply pressing the AE-Lock button to stop down the lens and take a meter reading. The onbody flash only fires at full power, making it difficult with pre-A lenses (a Flash Guide Number calculation is required). This lens mount includes DA and FA-J series lenses.
[edit] "Crippled" KAF2 mount
The "crippled" KAF2 mount is found on Pentax DSLRs released beginning with the K10D. It supports the extra features of the KAF2 mount including the two power contacts for the lens. Power zoom is supported (not full support and only in K10D), as well as lenses with focus motors. Such lenses support Supersonic Drive Motor (SDM), allowing for quieter autofocus. Like the "crippled" KAF mount, it does not have a mechanical stop-down coupler/indicator and thus can only use stop-down metering on pre-A lenses.
[edit] R-K mount
The R-K mount is a variation on the original K mount by Ricoh. It supports Ricoh's own implementation of shutter priority and auto exposure modes, similar to the KA mount but much simpler. The only addition to the original K mount is a small pin at the bottom which tells the body when the aperture ring has been set to the "P" setting (similar to the "A" setting on Pentax KA lenses).
Warning: This pin will catch on the drive-shaft hole in KAF and KAF2 cameras when turning the lens to lock it in place. It will jam part way and depending on the characteristics of this pin, it may be quite difficult to remove the lens from the camera.[2][3]
The R-K mount is used on Rikenon P lenses, Ricoh bodies that include the letter 'P' in their model number, and some non-Ricoh lenses. It is compatible with all other K-mount cameras and lenses when in manual or aperture-priority exposure modes, however the extra pin needs to be removed for safe use on autofocus Pentax cameras.
[edit] Adaptors
Pentax supplies adaptors to fit M42 screw-mount lenses and for lenses for its medium-format cameras, both the 645 and 6x7.
[edit] Cameras
[edit] PentaxManual focus
Auto focus
[edit] Chinon
[edit] Cosina
|
[edit] Miranda
[edit] Ricoh
[edit] Samsung[4][edit] SearsA lot of Sears cameras were made by Ricoh and use the Pentax K mount. Some are simply rebadged Ricoh models, while others are quite different.
[edit] Vivitar
[edit] Zenit
|
[edit] List of Lenses with any K-Mount Variant
- Cosina 40 f2.5
- Pentax 50 f1.2
- Pentax 50 f1.4
- Pentax 50 f1.7
- Revu 50 f1.2 (1975)
- Revuenon 135 f2.8
- Revuenon 55 f1.2
[edit] References
- ^ Bojidar Dimitrov's Pentax K-Mount Page. Retrieved on 2007-09-30.
- ^ Caution regarding Ricoh lenses on Pentax bodies. DPreview (December 17, 2004). Retrieved on 2007-07-24.
- ^ Sears 60-300 (auto aperture, push pull zoom). DPreview (July 15, 2006). Retrieved on 2007-07-24.
- ^ Samsung Digital Camera. Samsung Techwin (subsidiary of Samsung Group) (April 4, 2008). Retrieved on 2008-04-05.
![[1]](http://www.bdimitrov.de/kmp/bodies/photos/ME_F_AF35-70f2.8.jpg){kind=link}