The Pentax System Part #2 - K-mount

First- and Third-Generation K-mount Pentax Models

   Updated May 3, 2022

    Here is the second part of the fifth entry in our "Choosing a Vintage SLR System" series for manual focus SLRs. In Part #1 we looked at the Pentax M42 screwmount system. Pentax was the last of the "Big 5" (Canon, Minolta, Nikon, and Olympus being the others) to adopt a bayonet-style lensmount, doing so in 1975. The K-mount has continued to serve (in modified form) into the digital era. For now we will confine ourselves to the manual focus film era. So let's get to it with our standard format of: 1) Lenses, 2) Bodies, 3) Flash, 4) Accessories, and 5) Reliability & Servicing.

  Lenses

   Nomenclature. Ironically, the K-mount resulted from a short-lived collaboration between Pentax and Zeiss in the early-1970s. Both were hoping to make it a universal mount that they would license to other manufacturers. This was very similar to Zeiss' aim with the M42 mount decades earlier. The collaboration was short-lived, with Pentax ending up with the K-mount and the optical formulas for 15mm f/3.5 & 28mm f/2 lenses and Zeiss partnering with Yashica to produce the new CONTAX line of SLRs and lenses.

    There were three basic series of manual focus Pentax bayonet lenses: "K", "M", & "A". The "K" lenses had no visible marking designating them as such, just "SMC PENTAX" engraved on the front trim ring. The following two series were easily identified by an "-M" or "-A" suffix following "SMC PENTAX". "K" & "M" lenses were designed for use with manual and aperture-priority exposure modes. "A" lenses brought about the first major change to the lensmount to facilitate the program mode that became widely used in the early-1980s. There was a bit of overlap between the generations as certain low-production lenses, like the K-18/3.5 and 50/1.2 lived on through the "M" and up to the "A" era.

• "K" Lenses (1975-85) - The "K" series was a bit of an anomaly among Pentax lenses. Most of them were bumped up in size from their SMC Takumar predecessors although many of them retained the same optical formulas (the 28/3.5 being a notable exception). Standard filter size jumped to 52mm from 49mm, while 58mm and 67mm rounded out the range. A different pattern for the rubber focusing grip and the dropping of the "Takumar" designation served as a visual break from the last of the M42 screwmount lenses. Construction and build quality were otherwise much the same if not identical to the late SMC Taks. New prime lenses introduced in the "K" series included: 15/3.5, 18/3.5, 24/2.8, 28/2, 28/3.5 Shift, 30/2.8, 50/1.2, 85/2.2 Soft, 200/2.5, and the 2000/13.5 Reflex (Mirror). Four new zooms joined the lineup, with one model of the previous five-member SMC Zoom-Takumar line being dropped completely while the others were updated with the new mount and cosmetics. The "K" series lenses were sized to match the "K" bodies. With the debut of the Olympus OM SLRs and their very compact Zuiko lenses, Pentax felt the need to reclaim their previous role of leadership as the purveyor of the most compact and lightweight SLR system. In other words, the "Ks" needed to go on a diet...

• "M" Lenses (1976-83) - Put a wet "K" lens in the dryer and you would come up with an "M" version of the same lens. Wellll...that may be an oversimplification, but you get the basic idea :-). The name of the game was to cut size, weight, and costs with the "M" series. The size and weight part is understandable when looking at Olympus Zuiko lenses. But why the rush to cut costs? Another competitor, Canon, provided the impetus to do so. 1976 saw the debut of what became the best-selling manual focus SLR of all time, the Canon AE-1, aimed at the average consumer. Every other manufacturer, including Pentax, strove to keep up (or is that down?) in this race to the bottom of the market. Thus, it was not going to be enough to reduce only the size and weight of their lenses, costs would also have to come down to remain competitive. Heavier and costlier materials, such as brass, were reduced or eliminated and more plastics began to be used. Optical formulas were simplified wherever possible so that less glass could be used. Construction became more modular. In 1982, Pentax introduced a budget line of lenses called Takumar Bayonet. These lenses adopted simpler, cheaper coatings versus the standard SMC-Ms, in the vein of the Minolta Celtic and Nikon Series-E lenses. Optical performance was actually quite decent, aside from lesser flare and ghosting resistance. The lenses were now scaled to fit the new compact "M" bodies and returned to the 49mm standard filter size (with 58 & 77mm rounding out the range). While Pentax was able to maintain much of the quality feel of the original K series, many of the simplified designs (particularly the more budget-oriented lenses like the 28/3.5) did not hold the line optically. They were still "good enough", but the impact of the roll-backs in quality could not be denied. The late '70s also saw a big push in zoom development. Only two K-Zooms were carried over, with six new M-Zooms being introduced. M-Zoom optical performance was better across the board than the K-Zooms. Functionally, "M" lenses were identical to their short-lived ancestors. The next series would change that... 

• "A" Lenses (1983-2001) - The big thing in early-'80s SLRs was Program mode. This was another outgrowth of Canon's pioneering efforts to automate SLR operation to a level that would attract the typical non-enthusiast. Program enabled the camera to set both shutter speed and aperture automatically without any intervention from the photographer. Again, Pentax was forced to jump on the bandwagon or be left behind, and the biggest design change to the manual focus K-mount was set in motion. A series of electrical contacts was built in to the flange of the mount to convey information to the camera body from the lens. A new "A" setting followed the highest number on the aperture ring. A less-visible, but no less-important change was to the diaphragm actuator or lever. To allow for the precision necessary for Program and Shutter-priority modes, the operation of the lever was now linear, which meant that it now physically moved an equal distance between f-stop settings allowing for greater exposure accuracy. The exposure algorithms were now calculated using the area of the diaphragm opening rather than just its diameter. "A" lenses were fully backwards compatible with older "K" and "M" bodies. Other manufacturers made similar changes to the aperture operation of their lenses (Nikkor AI-s lenses had already adopted this same "linear" approach). "A" lenses adopted even more modular construction with ever-increasing use of plastics. This contributes to a cheaper feel with some of the budget-level lenses (particularly zooms). Optically, many "A" lenses improved on their "M" counterparts' performance and Pentax also introduced some new, high-performance optics such as: an updated version of the 15/3.5, a new 16/2.8 fisheye, 20/2.8, 85/1.4, 135/1.8, 200/2.8 ED (Extremely-low Dispersion glass), 200/4 Macro ED, 300/2.8 ED IF (Internal Focus), 400/2.8 ED IF, 600/5.6 ED IF, and 1200/8 ED IF. That's some heavy duty development, particularly in the telephotos as Pentax was trying to gain more traction with professionals. There was only one carryover from the M-Zoom lineup (the 24-50/4), and the design was revised and improved in the A-version. A pile of consumer-targeted zooms proliferated in A-series guise that were nothing special, as good old cost-cutting was the primary driver, not performance. The budget-oriented Takumar Bayonet line was modified to "A"-spec, as well. "A" lenses are highly sought-after by Pentax DSLR users as they offer full metering capability with the newer bodies which the "K" & "M" versions cannot. Standard filter size held at 49mm with 52, 58, 67, and 77mm filling out the line.    

    Features. Focal lengths covered a range of 15mm - 2000mm in the original "K" series of lenses. This dropped to 20mm - 2000mm in the "M" series, and then morphed into 15mm - 1200mm with the "A" series. "K" focusing helicoids retained the SMC Takumar construction of aluminum-on-brass for best feel and durability. A few "M" lenses did the same, but most "M" & "A" lenses moved to all-aluminum helicoid construction, excepting the higher-end lenses. They still provide very good feel but will not go as long between re-lubings as their predecessors. Aperture ring feel was excellent on "K" and very good on most "M" series lenses, but the consumer grade "A" zooms and primes do not hold to the same standard. Focus rings turn clockwise toward infinity and aperture numbers increase from right-to-left in typical Pentax fashion. All series featured Pentax' SMC lens coatings which were always among the best in the business, offering high contrast and color saturation, with excellent flare resistance.

    Noteworthy Lenses. From their short-lived collaboration with Zeiss, Pentax scored the optical designs for the K-15/3.5AL & K-28/2 lenses that are among the best lenses they ever made. The K-15/3.5AL (AL designated the use of AsphericaL elements) was short-lived, and is thus very rare, and was soon replaced with a standard spherical version. The K-series also brought a new design for the 28/3.5 that is definitely the best bang for your wide angle buck in the Pentax pantheon. The K-35/3.5 was the final version of one of Pentax' classics, and as a bonus was the lightest, most compact K and makes for a great walkabout or street lens. The K-50/1.4, 55/1.8 & 2, 85/1.8, 105/2.8, 120/2.8, and 200/4 are excellent lenses, too. As far as the M's go, the 50/1.4, 50/1.7, 85/2, 100/2.8 are probably the pick of the crop as far as standard focal lengths go. The M*300/4 was the best telephoto lens of the M-line by far, and was remarkably compact and light for its performance capability. It was the forerunner of the greatly expanded A* line which included: 85/1.4, 135/1.8, 200/2.8 ED, 200/4 Macro ED, 300/4, 300/2.8 ED IF, 400/2.8 ED IF, 600/5.6 ED IF, and 1200/8 ED IF lenses. Obviously, the big telephotos are more specialized and expensive but they were competitive with the offerings of the other manufacturers and demonstrated Pentax' lens-making prowess when they were not trying to economize. The spherical K 15/3.5 was modernized to "A"-spec with no other changes and remained the widest rectilinear MF Pentax lens. ​When it comes to zooms, the -M 35-70/2.8-3.5 & -M 75-150/4  are a steal of a deal at $60 -$100 USD apiece. In the "A"-lineup, the 24-50/4 & 35-105/3.5 are the two standouts at about $140 USD on average.

    Recommendations. With three generations of lenses, there are plenty of options that deserve consideration. So let's consider some generalities:

• If you already have or are considering a Pentax digital SLR, remember that only "A" lenses allow for automatic metering and auto-exposure on such bodies. "K" & "M" lenses only work in Manual mode and with stop-down metering on Pentax DSLRs. 
• Pentax was very strong when it came to normal lenses. The K-55/1.8, -M 50/1.7, and -A 50/1.7 were among the best moderate-aperture normal lenses available from any Japanese manufacturer. The 50/1.4s from all three series are well-regarded, and had 8-blade apertures versus the 6-blade versions of the moderate-aperture normal lenses. Some people prefer the 1.4's bokeh (out of focus rendering) to the that of the slower normals, but your mileage may vary ;-).
• Generally, "K" prime lenses are at least as good or a bit better optically than the corresponding "M" versions. This was due mostly to the simplification of many "M" optical designs which reduced the amount of glass elements to cut down size, weight, and cost. One exception was the M*300/4, which was the first of the famed "green-star" telephotos that expanded with the A-series to nine lenses. Such lenses were built to Pentax' highest standards. They handily outperform the standard telephotos and carry a price premium as a result. The rest of the A-series primes either match or exceed M-level performance and shave a few more grams of weight.
• When it comes to zooms, both the "M" & "A"-series outperform the "K"s with less weight and bulk due to improvements in zoom optical design. 
• See this article for a selection of the best bargains in "K" primes in comparison to their "M" descendants.

  Bodies

    There were three basic generations of manual focus K-mount bodies, just as there had been in the M42 screwmount era. There was also a certain amount of overlap in time between the generations. The breakdown was like this:

• 1975 - 1997 - The original K-bodies
• 1976 - 1987 - The M-bodies
• 1983 - 1997 - The A- & P-bodies

   
​    K-Series. Three different bodies were introduced with the K-mount in 1975, and two more in 1976. They closely followed the form factor and control layout of their M42 Spotmatic ancestors. Major changes included: depth of field (DOF) buttons on the bodies rather than the stop-down levers of the M42 lenses, new meters and viewfinder displays for the two-higher-end models, and power for the meters (and shutters on the electronic bodies) was now supplied by silver-oxide 357/SR44/S76 cells instead of the mercury cells of the Spottie era. There were a few cosmetic tweaks to the prism housings, the advance levers were a different shape and plastic-tipped, and the model designations were more prominent on the front of the cameras. 

• KM (1975) - This was the original base model of the K-series. It was basically a Spotmatic F with the following changes: the bayonet mount, no shutter release lock, the new DOF button, and the new power source for the meter. Other than the DOF button, control layout was identical to the F. The viewfinder and CdS (cadmium sulfide) metering system were exactly the same. There was a KM Motor version that was a special order item like the previous Spotmatic Motor models and was exceedingly rare as few people were interested in upgrading a base model with a motor drive at the time. Discontinued in 1976.

• KX (1975) - More than just a dolled-up KM, the KX was sort of a combination of the Spotmatic F and ESII models with some new bits thrown in. The top deck layout was much like the ESII. The KX sported a faster-reacting and more sensitive SPD (silicon photo diode) meter, a smoother film advance than the KM, and a brighter (+ 1/2-stop), more descriptive match-needle viewfinder display than the otherwise similar ESII's. It also featured a mirror lock-up (MLU) lever incorporated with the DOF button, and a wider ISO range of 8-6400, making it the top-of-the-line mechanical-shuttered Pentax at the time. The KX Motor option was available, too (and was about as rare as the KM version). Discontinued in 1976.  

• K2 (1975) - The K2 was the direct successor of the ESII, but with similar upgrades as the KX. Its biggest change was the introduction of the first vertical-travel shutter in a production Pentax. The shutter was electronically-controlled, with a mechanical back-up speed of 1/125 sec. This allowed for both manual and aperture-priority exposure modes. The next major change was the relocation of ISO settings and exposure compensation to a ring concentric to the lens mount. MLU was actuated by a lever on the left side (as you held the camera to your eye) of the lens mount, basically in the same spot as the older Spotmatic bodies had their metering switch. The K2 used a silver-coated pentaprism which made for a brighter viewfinder than in the KX (+ 1 1/2-stops), KM & K1000 (+ 2-stops) models. It was the most fully-featured body in the lineup at the time. Discontinued in 1980.  

• K1000 (1976) - The most famous K-body was, ironically, the most stripped-down, basic model. You can call it a KM with the self-timer and DOF deleted or an SP1000 with a K-mount and a hot shoe. Either way its sales success soon made the KM superfluous and that model was dropped in 1977. The K1000, meanwhile, went on to a 20+ year run and is probably the most famous student camera of the last 2 decades of the 20th century. Its long life saw changes in construction (read: cost-cutting) and movement of production from Japan...to Hong Kong...to China. Discontinued in 1997.

• K2DMD (1976) - The final K-series camera to be introduced was posited by Pentax to be fit for professionals. It was a K2 with eight improvements over the original with the two most noteworthy being highlighted in the model name. "DMD" stood for Data Motor Drive denoting the capability to mount a databack and/or motor drive. The prices for these two accessories were higher than both Nikon's & Canon's for their motor drives and databacks. That obstacle, along with no provision for interchangeable finders and only a few focusing screens that required a trip to a service center for installation, doomed the K2DMD as far as the pro market was concerned. Discontinued in 1980.

    Recommendations. The KX and KM are my picks for the best of the original bodies. There is no reason to buy a K1000 when you can get a KM for the less and have the DOF and self-timer features thrown in. The KX has a great meter and viewfinder and is about as reliable as you can get and more so than the K2. The K2 in original or DMD form often gets stiff in the operation of the ISO/Exposure Compensation ring and can also get a bit finicky electronically in its old age. Slip a K35/3.5 or 55/1.8 onto a KX and you have one of the all-time great combinations for photographic fulfillment. Of course, that is just my opinion. YMMV ;-). All that said, any original K can make great pictures and they feel great in your hands. Be aware that the mechanical Ks can all suffer from the same draggy 1/1000 sec. shutter speed syndrome inherited from the Spotmatics, particularly if the body in question has sat idle for a long time. I would say about 75% of the 25 or so mechanical 35mm Pentaxes of both M42 and K-mount persuasions that have passed through my hands have suffered from this. Nothing a CLA can't fix, but forewarned is forearmed :-).

    M-Series. The M-series was a direct response to the compact Olympus OM bodies. Pentax sought to reclaim their position as the builder of the tidiest SLRs and also outdo Olympus with bigger and brighter viewfinders. In 1976, only a year after the original Ks debuted, came Pentax' answers to the mechanical OM-1 and electronic OM-2...

• MX (1976) - Put a wet KX into the dryer...hmm...this is sounding too familiar ;-). The MX replaced the KX as the top-of-the-line mechanical body and was positioned as a direct competitor for the Olympus OM-1. Major changes from the KX (besides the size/weight reduction) were: a simplified viewfinder display with a semi-circular shutter speed setting and tri-color (red, yellow, green) LED metering readout versus the match-needle of the KX; the viewfinder now had 95% coverage at 0.97x versus 93% @ 0.88x; MLU was deleted; the (SPD) meter of the KX was replaced with a gallium arsenide phosphorus (GPD) meter which was not susceptible to the effects of infrared light on its readings as unfiltered SPD cells were (a blue filter was used to mitigate that issue); ISO range was reduced to 25-1600 from 8-6400; all MXs were motor drive-ready (up to 5 fps); there were now 8 interchangeable focusing screens available; the "magic finger" film loading replaced the traditional slotted reel to speed up film loading. Discontinued in 1985.

• ​​ME (1976) - The ME was a greater departure from the K2 as a new auto exposure-capable model than the MX/KX and was not intended as a direct replacement for the K2 or as a direct competitor for the Olympus OM-2. It was more of a foil to the Canon AE-1 in the consumer SLR market. While it retained the aperture-priority mode and single mechanical backup speed of the K2, there was no provision for manual exposure, MLU, DOF preview, aperture display in the viewfinder, or a motor drive (though it did accept the 1.5 fps ME winder). This stripping-down was necessary to meet the general price-point of the AE-1. The viewfinder was a Pentax giveth/Pentax taketh away situation: the 95% coverage of the K2 was reduced to 92% while magnification increased from 0.88x to 0.97x. As with the MX, a GPD replaced the SPD and LEDs replaced the match-needle readout of the K2, albeit in a different arrangement than the MX. ISO range was 12-1600 with exposure compensation of +/- 2 EV. Discontinued in 1980.

• ME super (1980) - Four years later, Pentax moved a bit upscale with the ME super, adding manual exposure, extending the top shutter speed to 1/2000 sec., while reducing the slowest speed to 4 sec. versus 8 sec., and increasing the mechanical backup speed to 1/125 sec. from 1/100 sec. There was also now a warning light in the viewfinder when exposure compensation was engaged. The LED display now used green LEDs for shutter speeds from 1/2000 to 1/60 sec., yellow LEDs from 1/30 to 4 sec. (to warn of possible blurring due to the slow speed), and red LEDs for the over-/under-exposure warnings. Fittingly (for the '80s :-)), the ME super introduced two push buttons for adjusting shutter speeds in manual mode, a pattern that would hold for several succeeding enthusiast/consumer models. The viewfinder maintained the 92% coverage of the original ME but reduced the magnification very slightly to 0.95x. The accessory MEII winder increased its top speed to 2 fps. Discontinued in 1987.

• MV (1980) - When replacing the ME, Pentax basically did so with two models, pushing upward with the aforementioned ME super, and dropping below with the MV. The full shutter speed viewfinder scale was replaced by a simple red-green-yellow three LED window, exposure was aperture-priority only, exposure compensation and the self-timer were deleted, and the GPD meter was replaced with an SPD that only measured from 3-19 EV versus 1-19 on the ME and ME super. More plastic was used in the construction and weight dropped to the lightest ever for a Pentax MF SLR, 420 grams. The final major trimming took place with the viewfinder, the magnification was dropped to 0.85x and the prism was now aluminum coated (versus the brighter silver coating of the ME/ME super) to save more money. Discontinued in 1982.

• MV 1 (1981) - The MV 1 appeared with a self-timer and the capability to accept the a winder. It was otherwise identical to the MV. Discontinued in 1982.
• ME F (late-1981) - The ME F was the first attempt at a production 35mm Auto Focus (AF) SLR (albeit, only if was used with an AF-capable lens ;-)). It was basically an ME super with the addition of an electronic module (Pentax called it "electronic-focus control" or EFC) that could be turned on to provide focus information to the simultaneously-introduced SMC Pentax AF ZOOM 35-70mm f/2.8 lens with a built-in focusing motor assembly. The lensmount was modified to KF spec, which meant that there were now electronic contacts in order for the body and lens to communicate with each other. (***NOTE*** Although the KF mount closely resembles the succeeding KA and KAF mounts, they are not the same electronically.) EFC could also be used as an electronic rangefinder with manual focus lenses. With the EFC switched off, the ME F operated exactly as an ME super would with all K-mount MF lenses with the standard split-image rangefinder/microprism collar focusing aid. Viewfinder coverage still held at the ME super's 92%, but magnification dropped to 0.87x, which was still very good and offered a bit more eye relief. The film wind throw was also shortened slightly from the ME super's to 130 degrees versus 135. Weight increased by 10% and two more SR44/357/S76 cells were required to power the camera (TIP: keep the EFC turned OFF and you will get even longer battery life than the excellent ME super's). Discontinued in 1984.

• MG (1982) - The final direct descendant of the ME was the MG. It utilized the same style viewfinder shutter speed display as the ME super, except that the speed range was only from 1/1000 to 1 sec. The viewfinder magnification was slightly better than the MV 1, at 0.87x, otherwise the two were identical apart from their viewfinder displays and the inclusion of another feature lifted from the ME super: the flash ready signal in the viewfinder via a second contact on the hot-shoe. The MG was the final M-series body and it replaced both the MV & MV 1 in one fell swoop. Discontinued in 1985.

    Recommendations. The MX is probably viewed by the majority of Pentaxians as the most desirable of the M-bodies. And if a mechanical shutter and compact dimensions/ low weight are high on your priority list, it is tough to beat. Here are a couple of caveats:

1. The lightness of the body means that there is less mass to absorb vibrations from the mirror and shutter in comparison to the KX. This was offset by the adoption of an air-dashpot damper for the mirror. The deletion of MLU also restricts the user from minimizing vibration when shooting on a tripod in macro or telephoto situations. Now, if you do not shoot in the 1/30 to 1 sec. range much, this is not going to be a big deal. Another penalty of the compact size of the MX (and any M-body, for that matter) is that longer & heavier lenses do not balance as well as they do on the larger K-bodies. Again, if you are not a telephoto shooter, this may not present a problem. Attaching a motor drive is one way to improve the balance of the MX with longer lenses.
2. That massive viewfinder is another drawing card for many people. The penalty for 95% coverage @ 0.97x magnification is minimal eye relief. If you wear glasses, you have no chance of utilizing the whole viewfinder on an MX. I do not wear glasses and I still have to jam my eye right against the eyepiece to see the whole thing. The structure of your face will determine if you can gain the full benefit of the MX' expansive view. Try before you buy, if at all possible. Be warned, if the MX viewfinder does work for you, it will spoil you as far as other cameras go ;-). 

    The ME super is perhaps the best all-rounder of the M-series. The viewfinder, while not quite at the level of the MX's, is still excellent and is more forgiving when it comes to eye-relief. Some people detest the push-buttons for shutter speed adjustment, for others it's not a big deal. The shutter itself is a good one, reliable as the tides, and that 1/2000 sec. top speed can come in handy in bright light or for stopping action. The viewfinder, while not quite at the level of the MX's, is still excellent and is more forgiving when it comes to eye-relief. The backup mechanical speed of 1/125 is a nice touch if the batteries die. One thing that might put some people off is the slightly longer travel of the shutter button. The ME F is often overlooked due to its rudimentary AF that was, at best, SLOWWWW and annoyingly jumped back and forth as its contrast-detect system hunted to find best focus. That has kept values lower, particularly if it is found with a standard M or A lens rather than the much rarer AF 35-70mm f/2.8 zoom (which pumps up the price considerably). The large battery door can be an issue as its opening mechanism's action is not readily apparent (the instruction sticker is often missing) and many have been damaged by overeager opening techniques. As long as the battery door checks out and the camera works, it is as good a buy as an ME super and functions identically. 

    The other M-bodies are certainly capable of taking fine pictures, but the effects of cost-cutting took their toll. Viewfinders are darker and more cramped relative to the MX & ME bodies. Compared to any modern consumer DSLR, though, an MV or MG is a picture window. Everything is relative :-).    

    LX. Deserving of its own section, the LX was the first and only truly professional Pentax body of the MF era. Introduced in 1980, the same year as the Nikon F3, it set new standards for weather-sealing. It featured such pro touches as: 8 interchangeable finders, 9 interchangeable focusing screens, wooden grips that could be customized to the individual user, a bulk film back, a 5 fps motor drive, and TTL (through the lens) flash (the first Pentax to have it). It had one of the most sensitive meters available at the time (-6.5 - 20 EV), with only the Olympus OM-2/2n coming close to its metered long-exposure capability. The shutter was a hybrid titanium-foil horizontal-travel unit that was completely electronically-controlled in aperture-priority automatic mode and used mechanical speeds from 1/2000 to 1/75 and electronic speeds from 1/60 to 4 seconds in manual mode. It also had the first proper multiple exposure function in a Pentax and MLU. It remained in production until the early 21st century, with a couple of limited editions along the way. LXs are still highly-regarded by most Pentaxians and due to their relative rarity (compared to Canon New F-1s and Nikon F3s) and build quality are definitely the most costly Pentax 35mm MF bodies to procure. A final limited edition (with matching A-50/1.2) was produced in 2001 before discontinuation. 

    A-/P-Series. The big goal of the Japanese SLR manufacturers in the early 1980s was to attract first-time buyers and so Program exposure modes became all the rage. The camera determined both shutter speed and aperture so the neophyte user wouldn't have to, so went the thinking. The KA mount, with its electronic contacts, debuted with this generation of Pentax SLRs. A-series lenses were required for Program mode to work with any of these bodies. Mechanical backup shutter speeds were eliminated.

• Super Program (1983) - AKA the Super A outside of North America, this was the most fully-featured amateur Pentax MF body. It followed the basic form of the ME super but with the addition of: the KA mount, a small (removable) handgrip, DOF preview, LCD viewfinder readouts for both shutter speed and aperture, and TTL flash. The Super Program also displayed the shutter speed on a top-deck LCD. The self-timer was now electronic instead of the clockwork style of the ME super. Besides Program, there were aperture-priority, shutter-priority and metered manual modes. The Seiko MFC-E2 shutter of the ME super was upgraded to an MFC-E3 and the shutter speed range expanded to 1/2000 - 15 sec. ISO range was also increased to 6-3200 from the 12-1600 of the ME super. The only area where the Super Program had a lower specification than the ME super was in regards to the viewfinder. While coverage remained 92%, magnification decreased from 0.95x to 0.82x, a noticeable drop. Discontinued in 1987.

• Program Plus (1984) - AKA the Program A outside of North America, this was a de-contented version of the Super Program. It used the lower-specced Seiko MFC-E5 shutter (top speed of 1/1000 sec.) and lost the shutter-priority capability, the exterior LCD, the TTL flash metering, and the internal LCD illuminator lamp of the Super Program. It does have far simpler and tidier circuitry than the Super Program, so there is less to go wrong electronically. Discontinued in 1988.

• A3/A3000 (1984) - The first Pentax with built-in film winding and DX film coding, the A3 was an entry-level model. Program and aperture-priority were the only exposure modes with no provision for manual override. A +1.5 EV exposure compensation button was the only means of adjusting exposure. Two AA batteries were supposed to be good for about 50 36-exp. rolls of film. Flash sync. speed dropped to 1/60 sec. Discontinued in 1987.
• P3/P30 (1985) - The first Pentax with an exposure lock, the P3 was otherwise a stripped-down, restyled Program Plus, with a shutter speed dial/mode selector replacing the push-button layout pioneered by the ME super. Aperture-priority mode was dropped, leaving Program and Manual. There was no provision for automatic winding. Flash sync. was 1/100 sec. Discontinued in 1988.
• P5/P50 (1985) -  Basically a replacement for the Program Plus, the P5 added a top-deck LCD display, DX film coding, exposure lock, and +/- 3 EV exposure compensation. Styling followed that of the P3. Discontinued in 1987.
• P3N/P30N (1988) - This update to the P3 added aperture-priority. Discontinued in 1990.
• P30T (1990) - Another update to the original P3, the only change was to a diagonal split-image rangefinder focusing aid. Discontinued in 1997.

    Recommendations. The Super Program and Program Plus were both high-value for the money entries versus their competitors when originally sold and are still relatively undervalued today. The Super Program is quite a bit more camera than, say a Minolta X-700, yet it routinely sells for 2/3s the price, and the Program Plus is generally half the cost of the Minolta. The Super Program also outdoes the ME Super (aside from the viewfinder) as far as specs go. The rest of the A & P-bodies were mainly targeted at entry level buyers. The A3/A3000 is kind of kludgy in the ergonomics department, with not much else to recommend it. As for the successive P-models, they can take fine pictures, are compact and light, and are dirt-cheap nowadays. They can make a great backup body if you so desire. Watch out for viewfinder/top deck LCDs that are faded or bleeding.

  Flash

    In the late '70s Pentax took control of its US distribution from Honeywell and began to provide its own branded flash units. (They had already introduced the Autorobo flash unit in non-US markets in 1973/74 with the Spotmatic F and ESII models.) The first models were auto sensor-equipped and progressed to TTL in the early '80s. They make excellent units for manual flash due to their low trigger voltages (under 8 volts) which will not harm modern digital bodies. Here is a brief outline of models and features:

• AF 080C Ring Light (1980) - The one and only macro flash from Pentax in the MF K-mount era. It offered TTL flash metering with the LX, Super Program, and Super A. There were also two manual power settings (full and 1/4). GN 8 at full power; 6 AAs; 49mm filter ring w/ adaptor for 52mm filter rings. ISO 6 - 800 w/ the LX; ISO 25 - 800 with the Super/Program/Super A.

• AF 16 (1977) - A basic, compact, low-powered unit intended for use with the compact M-bodies. As alluded to in its designation, the guide number (GN) was 16 (meters @ ISO 100). It had two auto settings, plus full-power manual. ISO range was 25 - 400. There was no bounce or swivel provision. It used 2 AA batteries (alkalines only; no Ni-cads) and had a single contact for X-sync and a socket for a PC cable. The AF16 ostensibly covered a 28mm lens' field of view (FOV). (This was a bit optimistic ;-)) 102 grams w/o batteries.

• AF 160 (1980) - Basically an AF16 with a second electronic contact for use with the ME super, MV & MG SLRs and their flash-ready lamps in the viewfinder. With such bodies, the unit also automatically set the flash-sync speed, eliminating the process of the photographer having to manually set the sync. speed on the camera body as previous Pentax bodies & flash units required. Output was the same (GN 16), but the flash duration range was reduced to 1/30,000 - 1/5000 sec. from the 1/40,000 - 1/4000 sec. of its predecessor. Recycling also took 33% longer (8 sec. vs. 6 sec.). Otherwise, it was identical to the AF16. 145 grams with batteries.

• AF 160S (1981) - The "S" suffix was added to indicate that this was a "dedicated" flash for Pentax SLRs. (This meant that the contact configuration on the hotshoe was specifically intended to interface with Pentax cameras to allow the full range of features to be utilized.) The only difference from its predecessor was a further reduction of the flash duration range to 1/15,000 - 1/3000 sec. Otherwise identical to the AF160. 100 grams w/o batteries.

• AF 160Sa (1988) - The final GN 16 flash of the MF era had a taller form factor and was designed for use as a basic flash with the Program mode Pentax SLRs. It automatically set the aperture to a single value and then matched the shutter speed to that setting. It was not a TTL flash. Duration was extended to 1/30,000 - 1/2000 sec. and recycle time returned to the 6 sec. figure of the original AF16. ISO 25 - 400. 105 grams w/o batteries.

• AF 200S (1980) - This unit was 25% more powerful and twice the weight of the AF 160S. It used 4 AAs and recycled in 6 sec. It offered the same interface with the ME super, MV, and MG as the AF 160S. ISO range was 25 - 800. It had two Auto settings as well as full manual. Flash duration ranged from 1/30,000 - 1/1500 sec. The AF 200S could cover up to a 24mm FOV with the accessory AFW1 wide-angle adapter. This diffuser also improved coverage with 28mm & 30mm lenses. Can use alkaline or Ni-cad batteries. 285 grams with batteries.

• AF 200T (1984) - An improved AF 200S, with TTL capability via a third contact on the hotshoe with appropriate Pentax SLRs (LX, Super Program/Super A, certain 645, and the 67II medium format bodies, 35mm AF, and even some early Pentax DSLRs). Along with this, it retained the two auto settings and had four manual power settings (full, 1/2, 1/4, 1/8) making it a very versatile little flash. All other specs are identical to the AF 200S. 175 grams w/o batteries.

• AF 200Sa (1988) - A stripped-down AF 200S, this was a basic flash that operated in the same fashion as the AF 160Sa with Program-capable Pentax SLRs. The AF 200Sa used the same wide-angle adapter at the AF 200S, but had a reduced duration range of 1/15,000 - 1/2500 sec., and recycling took 33% longer (8 vs. 6 sec.). ISO range was 25 -1600. 160 grams w/o batteries.

• AF 201Sa (1990) - Basically a lower-profile version of the AF 200Sa, it had coverage for a 35mm lens. It had no provision for a wide-angle adapter. 140 grams w/o batteries.

• AF 220T (mid-'80s) - A basic TTL flash with bounce capability. ISO range 25 - 1600. It was intended primarily for use with Program mode Pentax SLRs although it could be used with aperture-priority or manual modes if the user consulted a chart in the user manual and set the camera accordingly. GN 22; 4 AAs; recycle time of 6 sec. 165 grams w/o batteries.

• AF 240Z (1986) - Pentax' first zoom-head flash, covering 35 - 135mm lenses. While it could be used with Program-mode, aperture-priority and manual cameras, it was not TTL-capable. It used a set aperture as described in the bullet featuring the AF 160Sa. GN 24 @ ISO 100 and at the 50mm zoom setting. It also had the bounce feature, took 4 AAs, and recycled in 7 sec. 220 grams w/o batteries.

• AF 260Sa (1990) - This was basically a higher-powered version of the AF 160Sa. GN 26; ISO range of 25 - 800; 7 sec. recycling; 1/15,000 - 1/1000 sec. duration. There was a wide-angle diffuser that extended coverage to 28mm lenses. Non-TTL. 4 AAs. 175 grams w/o batteries.

• AF 280T (1982) - Pentax' highest specified shoe-mount TTL flash when it was introduced. GN 28; ISO range of 25 - 800; TTL setting; two auto settings; two manual settings (full & approx. 1/16); tilt & swivel; 8 sec. recycling; uses the same wide and tele adapters as the AF 200 series.

• AF 400T (1980) - The full-on professional "potato masher". The AF 400T was introduced with the LX as the first TTL Pentax flash and it came with a bevy of features: bounce/swivel head; three auto settings; four manual settings (full, 1/4, 1/16, 1/25);  6 AA batteries (alkaline or Ni-cad) in the UM-3 battery pack; TR & 510 shoulder mount power packs for longer life/faster recycling; AFW2 & AFT2 adapters to cover 24 - 200mm lenses; AF 400T clamp & bracket sold separately. Weight was 770 grams w/o batteries or bracket.

    Recommendations. If you are serious about a bounce/swivel hotshoe-mounted flash unit that will provide TTL with a Super Program or other TTL-capable MF body, you would do well to check out the autofocus-era AF 500FTZ, which is backward compatible with such bodies. It has six (count 'em) manual power settings along with a power-zooming head that covers from 24 - 85mm lenses. It is a powerful beast for its size (GN 42). If you are just looking for a compact little unit for on/off camera use, the AF 200T is a sweet little package with its 4 manual settings along with its auto and TTL capabilities. It also is half the weight and size of the AF 500 FTZ. Even the AF 16 & 160 make for a simple, super-compact short-range fill flash. 

  Accessories

​    Motor Drives & Winders. Until the debut of the M-series bodies, Pentax motor drives were uncommon and expensive.

• KX and KM motor drive models were special order and rare and not very ergonomic, with a tall vertical grip containing the batteries attached to the bottom of the drive beneath the camera.
• The K2DMD (1976) motor drive and databack were very expensive and as a result are prized by collectors. The grip and battery pack were separate components. Top speed was 2 fps at shutter speeds 1/60 sec. and faster. 12 AAs in Battery Grip M (18 V) gave a maximum of 40 rolls of 36 exposures.
• The Motor Drive MX (1976) offered more power and grip options. Top speed was 5 fps. Battery Grip M gave a maximum of 100 rolls of 36-exp. and the Ni-cad Battery Pack M (14.4 V) gave 40 rolls of 36-exp. 
• The Winder ME (1976) maxed out at 1.5 fps and at least 20 36-exp. rolls from its 6 AAs (alkaline only). Winder MEII (1980) was compatible with the ME super, MG, MV-1, Super Program/Super A, Program Plus/Program A, and P50/P5 bodies. It was boosted to 2 fps and would give a minimum of 20 36-exp but now with only 4 AAs. 
• Motor Drive A (1983) was exclusive to the Super Program/Super A, Program Plus/Program A, and P50/P5 SLRs. It used Battery Pack A with 8 AAs (alkaline or Ni-cad), and would give approx. 100 36-exp. rolls per set of batteries. Top speed was 3.5 fps in Continuous High; 2 fps in Continuous Low; there was also a Single shot mode. It was the first Pentax motor drive to feature a vertically-oriented shutter release to go with the traditional horizontal location.

    Focusing Screens. With the K-series the only options for a different focusing screen were: 1) to order the camera with your desired screen, or 2) to go to a Pentax Service center to have the other screen installed after the fact. And there were only two screens initially available: 1) matte with central microprism patch, 2) matte with central split-image rangefinder. The K2DMD was the first Pentax to come with a combined matte/central split-image rangefinder with surrounding microprism collar.

   The MX was the first Pentax with user-interchangeable screens and access was through the open lens mount (a la the Olympus OM-1). Aside from the now-standard matte/split-image w/microprism collar, there were seven available screens. It was the only M-series body to offer this option.

   The professional LX was the last MF Pentax to feature interchangeable focusing screens. Because it also had interchangeable finders, the drop-in screens were changed with the finder removed. As noted earlier, there were 9 different screens available, some for general use and the others for more specialized work. 

    Miscellaneous. The usual suspects such as extension tubes, bellows, copy stands, were all available in K-mount. When the KA mount was introduced, many lens accessories were updated with electronic contacts to permit full metering capability. 

  Reliability and Servicing

      The KX, KM, early K1000s, and MX were probably the most reliable mechanical bodies of the MF K-mount era. Most of their internals had been proven in the Spotmatics and were simple to repair if the need arose. The LX was, of course, intended to withstand punishment from pros. It was sealed with silicone during construction, so having to service it meant breaking those seals and it would not retain the same level of weather and dust sealing afterward (unless you had an ultra-dedicated repair tech :-)). Unfortunately for the LX, its electronics seem to be its greatest enemy as it ages into its fourth decade. For the price you pay for one nowadays, they are a bit sketchy for me personally. YMMV.  Same goes for the K2. 

     As for the remaining electronic models: the ME super, Super Program/Super A, and Program Plus/Program A were quite reliable and their electronic quartz-timed shutters retained their accuracy longer than a mechanical shutter could. Pentax had some of the tidiest circuitry of any SLR manufacturer, showing a high level of attention to detail in most cases. Even the base models can often be found working well after three or four decades, although the feel of their push buttons and other controls is distinctly cheaper. As with most electronic MF systems, the mid-'70s to early-'80s was the high-water mark. Post-1985, auto focus became the big thing and MF development at best stagnated and at worst regressed.

    Lenses are easily serviced on the whole, if necessary, with only the consumer "A" zooms feeling really cheap and not terribly sturdy. The higher-end lenses were built as well as anything that came out of Japan in the era and are still impressive today. Most accessories are a definite cut above aftermarket alternatives.

  Conclusion

    The continued existence of the K-mount for over 4 decades now makes it one of the higher-demand vintage systems, at least among Pentaxians ;-). This can drive prices up for some of the higher-spec lenses and bodies. Pentax LXs are just as expensive nowadays as Nikon F3s, and "A" lenses, because of their compatibility with modern DSLRs can also bring a pretty penny. If you value portability and forward compatibility with DSLRs, do yourself a favor and check out the Pentax MF K-mount system :-).

  
  References:

    Pentax Forums @ https://www.pentaxforums.com/camerareviews/
    The History of the Penta Prism SLR @ http://www.pentax-slr.com/
    Japanese SLR Production Numbers @ http://knippsen.blogspot.ca/
    Various Pentax User Manuals @ http://www.butkus.org/chinon/pentax.htm
    Various Pentax Flash User Manuals @ http://www.butkus.org