Updated Aug. 22, 2021
Here is the final edition of 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.
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.
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:
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:
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.
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 same price 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...
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:
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 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 other M-bodies are certainly capable of taking great pictures, but the effects of cost-cutting took their toll. Viewfinders are darker and more cramped relative to the MX & ME. 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.
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.
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:
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.
Motor Drives & Winders. Until the debut of the M-series bodies, Pentax motor drives were uncommon and expensive.
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.
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 :-).
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
Suffers from a two-decade and counting film and manual focus SLR addiction. Has recently expanded into 1980's AF point and shoots, and (gack!) '90s SLRs. He even mixes in some digital. Definitely a sick man.