The Pentax System Part #1 - M42 Screwmount

Spotties of the Seventies

  Updated Apr. 27, 2022

    Greetings, and welcome to our fifth vintage SLR system overview, this time featuring Pentax (or Asahi Optical Co. as they were originally known). In this installment we will examine their first SLR system, which (aside from the Asahiflex models) utilized the M42 screwmount introduced by Zeiss in 1949. Over time, such was their success, M42 became commonly referred to as the Pentax screwmount. The M42 mount was used by Pentax for 20 years (1957-76) and today represents one of the most affordable and accessible SLR systems available to the vintage-focused photographer. In the second part of our Pentax overview, we will dig into the bayonet-style K-mount system introduced in 1975, and which is still used (in a modernized electronic form) by Pentax. As usual, we will break things down by: 1) Lenses, 2) Bodies, 3) Flash, 4) Accessories, 5) Reliability & Servicing.

    In 1952, the Asahi Optical Company introduced its first SLR, the Asahiflex, in contrast to the other Japanese manufacturers who had made rangefinders their mainstay. The German Praktiflex of 1939 served as the basis for this model. It used the M37 (its metric thread designation) screwmount and had a waist-level viewfinder. The Asahiflex was basically a straight copy of the Praktiflex, but with the introduction of the IIb model, Asahi introduced the first quick return mirror on a Japanese SLR. They had now set out on a continual program of improvement and automation that would kickstart the Japanese SLR industry that came to dominate the world market. For our purposes, we will pick up the trail in 1957, when Asahi introduced its first pentaprism-equipped (for right-side-up, un-reversed viewing) M42 mount SLR -- the PENTAX (derived from PENTAprism and AsahifleX). 

  Lenses

    Takumar. This was the designation chosen by Kumao Kajiwara, founder of Asahi, for the lenses that would grace his company's SLR cameras. He derived the name from his brother's given name, Takuma Kajiwara. Asahi was heavily influenced by Zeiss' approach to optics and that was who they measured themselves against. The Takumar family of lenses went on to build a fine reputation for both optical quality and some of the best, if not the best, mechanical quality of the Big 5 Japanese manufacturers. (Into the early 1970's there were four major Japanese SLR companies. Besides Asahi Pentax, there was Canon, Minolta, and Nikon. Olympus elbowed their way in with their innovative OM series of SLRs in the mid-'70s and brought the number to five.) They are a joy to use. Focusing and aperture rings were oriented in the general Zeiss fashion, with the focus ring turning clockwise toward infinity, and aperture numbers increasing from right to left (aside from one exception :-)). 

​    Takumar Nomenclature. There were five main variations of Takumar lenses. They can be easily differentiated by the name engraved on the front trim ring of the lens:

• Takumar - These used a pre-set aperture, meaning that there were two rings, one that set the aperture value and a second one that the photographer turned to physically open or close the diaphragm itself. In other words, a manual aperture system. Aperture and preset rings were located at the front of the lens. The earliest Takumars were the M37 lenses for the Asahiflex SLRs, and many of these designs were carried over into M42 when the Asahi Pentax was introduced. Early Takumars had silver-colored aperture rings and DOF (depth of field) scales, but these started changing to black in 1960. Some Takumars were produced into the late-'60s, but, by and large, they were superceded by Auto Takumars by the early-'60s.

• Auto Takumar - First introduced a year after the M42 Takumars, in 1958-59. Although named Auto Takumars, these were really semi-automatic aperture lenses. There was now a stop-down lever that the photographer pushed to open the aperture prior to exposure and a pin on the lens mount that was actuated by the camera to stop the aperture down when the shutter button was pressed. The preset ring was thus eliminated. Early Auto Taks retained the forward aperture ring location, but soon began relocating it to the rear of the lens. As with regular Takumars, many Auto Taks started out with silver aperture rings and DOF scales, but most of them changed to black during 1960, although some retained their two-tone style into 1961. Lens coatings also began to be improved during this time. Earlier, we referred to one exception to the typical aperture numbering arrangement, and here it it is: a new version of the 55mm f/1.8 Auto Takumar (1960) had the aperture values increasing from left-to-right. This served to differentiate it from the previous version, which also featured a "zebra" style focusing ring, with polished smooth panels alternating with the black-painted knurled parts of the grip.  It also sported a "flat" focusing grip as opposed to the standard slightly-scalloped grip of the other Auto Taks. This new 55/1.8 also sported a truly automatic aperture and that actually made it the first of the...

• Super Takumars - The first officially-labelled Super Taks appeared in 1962. The big advances were the fully automatic aperture (with SLRs from the S3 and up) and more advanced coatings. Super Taks also adopted the new auto/manual stop-down lever introduced on the final 55/1.8 Auto Tak. The appearance of the entire lineup was now more coordinated, with all-black finishes and the same style of grip knurling. The first 55/1.8 Super Taks carried over the reversed aperture ring labeling of the late Auto Tak version. This new 55/1.8 adopted the standard Pentax aperture labeling but with the same flat, fine-knurled aperture grip. This style continued until the second iteration of Super Takumars appeared around 1965. These Super Taks featured a scalloped aperture ring to match the pattern of the focusing ring. They also saw changes to some of their optical formulas and constructions, and certain lenses (such as the 55/1.8 & /2 and the 7-element 50/1.4) adopted elements with thorium added to increase their refractive index. Thorium is radioactive and some people are not comfortable with it. Others have no problem as it was not used in the eyepieces of Pentax SLRs where such close exposure could damage the eye. Affected lenses are discussed in more detail below. Super Takumars stayed in production until 1971, making them the most plentiful of all M42 Pentax lenses, and therefore, the most affordable. The next thing on Pentax' list was to provide full-aperture metering as well as make its biggest jump so far in lens coating technology. That brings us to the...

• Super-Multi-Coated Takumars - The adoption of the seven-layer Super-Multi-Coating technology pushed Pentax to the forefront of the industry as far as contrast and flare-resistance was concerned. SMC did much to establish the now-familiar high-contrast, high-color-saturation Pentax "look". The other big advance with this series of lenses was the reworked aperture-actuation mechanism that offered automatic full-aperture (no stopping down needed for an accurate meter reading) metering with bodies equipped for it (the Electro Spotmatic, ES, and the Spotmatic F). They retained full backward compatibility with the standard automatic aperture bodies. Styling remained the same as that of the Super Takumars. New lenses were: the 100/4 macro and the 120/2.8 telephoto.

• SMC Takumars - The final generation of M42 screwmount Takumars debuted in 1973. Changes were mostly cosmetic, with a new rubber focus grip and Super-Multi-Coated was now abbreviated to SMC on the front trim ring. Aperture rings returned to a flat profile but with coarse knurling. The only new lens introduced was the ultra-wide angle 15/3.5.

    Features. Focal lengths eventually covered from 17mm to 1000mm in Pentax M42. Early on, there was coverage from 35mm to 1000mm. Focusing helicoids were aluminum-on-brass, providing the best feel and wear characteristics. It took Minolta until 1966 to come close to the feel of the Takumars and Nikon never did. Pentax also led the way when it came to coatings among the Japanese manufacturers, particularly when they introduced S(uper) M(ulti)  C(oating) in 1971. Among the Big 4, Pentax had the most compact lenses and often the lightest, despite their solid construction. As noted above, there were a few lenses that used radioactive rare-earth elements to increase the refractive index of the glass used in them. The decay of such elements does impair the optical performance of such lenses. Fortunately, with UV treatment, that performance can be restored. Pre-SMC Takumars have a bit less contrast and color saturation than their descendants, which is preferable to some people. The standard filter size was 49mm, with 58mm and 67mm rounding out the regular lineup. A few of the early Takumars used the 46mm size, and there was the odd 55mm and 62mm thrown in for good measure.

    Noteworthy Lenses. Pentax was the first Japanese manufacturer to produce a wide angle (35mm f/4) lens for an SLR. Within three years, they had improved it into the 35/3.5, which stayed in production (with improvements in coatings and glass, but the same optical formula) into the K-mount era. Its small size and simple construction, together with its very credible performance make it an excellent lens that no M42 Pentaxian should be without. The fact that it is also one of the least expensive Takumars is just icing on the cake. For about five times the cost, on average, the 35/2.3 Auto Takumar is a very unique lens, its character changing with every stop of the aperture.

​    When it comes to normal lenses, the 55/1.8 (and its 55/2 sister lens on the lower-end bodies) in its many guises was one of the finest kit lenses from any Japanese manufacturer. Good samples give up little to the more acclaimed 50/1.4s. Speaking of the fast 50s, you will probably not find a more-hyped Super Takumar than the quasi-"divine" eight-element first version from 1964-65. Claims that its continued production would have bankrupted Asahi have only added to the mystique of this lens. However, the seven-element version had lower production costs, with good samples offering equivalent-or-better performance to their illustrious predecessor. 

    The short telephoto Takumars were well-regarded and even today fetch strong (cough-cough ;-)) prices. Although varying in construction and character, the 83/1.9 Takumar, 85/1.8 Auto and Super-Multi-Coated Takumars, and the 85/1.9 Super and Super-Multi-Coated Takumars all offer excellent performance. The 85/1.9 is generally viewed as the weakest of the three and sells for $225 - $300 USD. For an 85/1.8, tack on another $100 USD on average. The 83/1.9 is much rarer and a collectible and lives in the $1000 + USD range. Less-recognized is the 105/2.8, which came in two different optical constructions and five generations. While not as highly-regarded as the 85s, the 105s are much more affordable ($100 USD or so) and very good lenses in their own right. 

    Pentax was one of the first companies to use fluorite and quartz in lenses. There was the 85/3.5 Quartz Takumar (introduced in 1963) for use with bellows and the Ultra-Achromatic-Takumar 85/4.5 & 300/5.6 (1968) lenses for UV, infrared and standard photography. These are specialized, truly rare pieces, and very pricey as a result.

    Radioactive Lenses. This can be a hot topic ;-). It is very much a personal decision as to whether you will use one of these lenses. Research it thoroughly before making a decision. What we will discuss here are the lenses that have thorium elements and how to maximize their performance if you choose to use them. The most visible problem with thorium lenses is their tendency to develop a yellow to brownish color cast as the thorium decays. *NOTE* Not all yellowing is due to radioactive decay, in some (rare) situations it is the deterioration of the Canada balsam used to cement elements together. Here is a list of Super & SMC Takumars confirmed to be radioactive:

• 35/2 Super & SMC Takumar
• 55/1.8 & /2 Super & SMC Takumars. All Super Takumars with a flat, fine-knurled (read: non-scalloped) aperture ring are not radioactive. All other 55/1.8 & /2 Super, Super-Multi-Coated Takumars are. Pentax revised the design to delete the thorium element at some point during the final SMC Takumar generation, which then carried over into the K-mount version. So it is possible to get a non-radioactive version of the 55/1.8 SMC Tak.
• 50/1.4 Super & SMC Takumar (all 7-element versions). The original 8-element Super Takumar 50/1.4 is not radioactive. Very late-production copies of that version have been found to have a mildly-radioactive element (about 1/50 the level of the subsequent 7-element version). The best way to differentiate the eight- and seven-element types is to examine the rear element. The retaining ring on the 8-element only meets the edge of the glass and has been machined with slight relief at that edge. On the 7-element version, the retaining ring cups slightly around the edge of the rear element. A secondary, and somewhat less reliable, point of identification is the location of the Infrared (IR) index (the little red "R" or red line) on the depth of field scale. Almost always, the 8-element version has the mark on the right side of the f/4 mark on the scale, whereas on the 7-element lens, the IR index is to the left of the f/4 mark. The only exceptions have been a couple of instances reported where a 7-element had the index mark on the right side of f/4, very likely as a result of parts-bin sharing during the production transition from the 8 to the 7.
• 50/4 Macro Takumar - About 1/30th the radioactive level of the 7-element SMC 50/1.4.

   The yellow to brownish color cast that results from the decay of thorium can be reduced or eliminated, depending on the severity, by exposure to UV light. There are a number of methods described online. One that has worked for me is a small IKEA desk lamp that emits enough UV light with its standard LED bulb to cure the color cast after a few weeks. If you are using a dedicated UV lamp that gets hot, be careful not to heat the lens up excessively, as this can cause separation of cemented elements and migration of lubricants to places you don't want lubricants to migrate ;-). The UV treatment is not just for cosmetics, it restores the optical performance of the lens.   

    Recommendations. In Takumarland, the moderate-aperture lenses (28/3.5, 35/3.5, 55/1.8 & 2, 105/2.8, 135/3.5, 150/4) offer a wonderful balance of performance in a tiny package for very reasonable prices. They are definitely worth a hard look for someone just getting into the system. Many Pentaxians prefer the look that the 50/1.4s give, and they are a good value for the money, too. If you are looking at adapting M42 Takumars to other brands of cameras, be aware that the Super-Multi-Coated and SMC versions can have interference problems with some adapters due to the location of the open-aperture metering lug on the lens-mounting flange.  

  Bodies

    There were three basic eras (with some overlap) of Asahi Pentax M42 SLRs:

• 1957 - 1969 - the original Pentax and its immediate descendants with no internal meter and fully mechanical operation. Aperture actuation progressed from fully manual to semi-automatic to fully automatic by 1962.
• 1964 - 1977 - the Pentax Spotmatic and its progeny. Integrated metering for nearly every model with fully mechanical shutters.
• 1971 - 1976 - the Pentax Electro Spotmatic and its successors. Electronically-controlled shutters and aperture-priority autoexposure were the order of the day.

    Asahi not only produced SLRs under its own brand but also was an OEM supplier for Sears in the USA during the late 1950's under the "Tower" brand. When the 1960s came along, in the US market, Pentax bodies were initially badged as "Honeywell Heiland Pentax" and later "Honeywell Pentax" denoting the local distributor. In the rest of the world, "Asahi Pentax" was the common designation. An exception was in South Africa (and possibly some other small markets), where the "Pentax" designation was still owned by Zeiss/Pentacon, so the SLRs were called "Asahiflex", "Penta Asahiflex", or "Asahi Pentar".  

   First-Generation Mechanical Bodies   

• 1957 - Asahi Pentax (aka AP or Tower 26). The replacement for the Asahiflex IIa (1955). This camera featured a pentaprism viewfinder (offering upright, un-reversed viewing), an instant-return mirror, and a right-side mounted film advance lever (not a knob as was common previously). This configuration would not only set the pattern for future Pentax models but also the Japanese SLR industry as a whole for decades. There were two shutter speed dials, one for "high" speeds (1/25 - 1/500 sec.) and slow speeds (1/10 to 1 sec. and T for Time exposures). There were FP and X terminals for flash with X-sync being 1/50 sec. Standard lenses were: 58/2, 55/2.2, and 58/2.4 Takumars. Body discontinued in 1958. Nearly 20,000 produced.

• 1958 - Asahi Pentax S (aka Tower 26). Shutter speeds were now labelled 500-250-125-60-30-15-8-4-2-1 instead of 500-200-100-50-25-10-5-2-1. "S" was now stamped below the serial number on the left shoulder of the camera on Asahi Pentax versions. ASA film speeds were now printed on the ASA dial itself instead of engraved on the top plate of the camera. Standard lenses were the 55/2.2 and 55/1.8 Takumars. Body discontinued in 1959. It is estimated that less than 5,000 were produced.

• 1958 - Asahi Pentax K (aka Tower 29). Two months after the debut of the S, Pentax brought out the improved K. The top shutter speed was now 1/1000 sec. But more importantly, aperture operation became semi-automatic. The camera now stopped down the aperture automatically right before exposure, although the photographer still had to manually re-open it after by means of a lever on the lens. The standard lens was the new 55/1.8 Auto Takumar. Body discontinued in 1959. Over 21,000 produced.

• 1959 - Asahi Pentax S2/H2/SB (aka Honeywell Heiland H2). There was now only a single, non-rotating shutter speed dial (previously the dial rotated when the shutter was released). The top shutter speed was the 1/500 sec. of the original S. Making its first appearance was the soon-to-be familiar orange cocking indicator on the top right shoulder of the camera. The S2 also was the first Pentax with a central microprism focusing aid accompanying the Fresnel focusing screen. Now, for the plethora of model names: S2 was the standard Japanese and international designation; H2 was used in certain small international markets such as South Africa; SB was sold only to the Japanese military; and finally, the first Honeywell-badged H2 versions appeared in the USA. Heiland was the division of Honeywell that handled photo products, and so appeared on the prism housing in place of Asahi. In time, Heiland was dropped from the nomenclature. Later-production S2s had a notch machined in the shutter speed dial to index with the new Pentax Clip-on Exposure meter. The standard lens was a 55/2 Auto Takumar. Body discontinued in 1963. Nearly 131,000 produced.

• 1960 - Asahi Pentax S3/SB2 (aka Honeywell H3). Very early in S3 production, the top shutter speed was raised back to the 1/1000 sec. of the K. But the big advance was the introduction of fully automatic aperture operation with the new 55/1.8 Auto Takumar kit lens. This was actually the first of what would be called the Super Takumars when it came to aperture function. The familiar Auto/Manual lever appeared with this lens. Like the S2, later-production S3s had the meter coupling notch on the shutter speed dial. Again, the SB2 was a rare Japanese military version. Body discontinued in 1969. Over 361,000 produced.

• 1961 - Asahi Pentax S1 (aka Honeywell H1). This was the first budget model introduced by Asahi. It was basically an S3 without the 1/1000 sec. speed and a different kit lens, the 55/2.2 Auto Takumar (this was still a standard Auto Takumar with the lever to re-open the aperture after exposure). Pentax would use this strategy again in the future. The detent for 1/1000 sec. was still there on the shutter dial, but there was no cam to regulate the speed, even though the shutter would fire at this "phantom" setting. The simplified construction reduced the assembly and calibration costs of the camera, and taken with the less sophisticated 55/2.2 kit lens, allowed Asahi to lower the price from that of the S3/H3. Body discontinued in 1963. Actual production approximately 47,000.

• 1962 - Asahi Pentax SV (aka Honeywell H3v). The final top-end model of the original Asahi Pentax line and the first Pentax with a self-timer. It also introduced the first enclosed, self-resetting exposure counter to the lineup. Other than those improvements, it was basically the same as the S3/H3. There were two versions of the SV, differentiated by the color of the "R" on the rewind knob. A green "R" signified the early edition that was not compatible with the new 50/1.4 Super Takumar lens that debuted in late-1964. An orange "R" indicated compatibility with the new 50/1.4. To confirm compatibility for sure, look for a crescent-shaped push plate in the throat of the body. The standard kit lens was now called the 55/1.8 Super Takumar, although it was otherwise identical to the late Auto Takumar that came with the S3. Body discontinued in 1968. Over 482,000 produced.
• 1962 - Asahi Pentax S1a (aka Honeywell H1a). Following the pattern set with the S1 as a more budget-friendly version of the S3, the S1a was a de-contented SV. It did retain the new enclosed exposure counter, but was limited to 1/500 sec. as the top shutter speed. Again, as with the S1, there was the unmarked detent on the shutter speed dial where 1/1000 was on the higher-end models. The S1a/H1a also came in the same early "R"/later "R" versions as the SV that indicated compatibility with the 50/1.4 Super Takumar. The standard kit lens was the 55/2 Super Takumar. Body discontinued in 1968. Approximately 135,000 produced.

• 1962 - Asahi Pentax Super S2. This was a Japanese market-only SLR. To make things confusing it was only marked S2, just like the original 1959 version. To make matters worse, there were two series of the Super S2 and two versions of the second series. So let's try and figure this out. The first edition was basically an S3, with its 1/1000 top speed, but marked S2 on the top plate. So there is the first clue: if you find an S2 with the 1/1000 setting on the shutter speed dial, it is actually a Super S2. The kit lens was the new Super Takumar 55/2. The second series adopted the new enclosed, self-resetting exposure counter of the SV. In this series, the S2 also adopted the R/R rewind knob markings of the SV and S1a indicating whether the 50/1.4 Super Tak could be used on the body (remember: green means No and orange means Yes). The standard lenses on the second-gen versions were the 55/2 & 55/1.8 Super Takumars. Body discontinued in 1968. Clear as mud, I hope ;-). An estimated 52,000 were produced. ​  

    Recommendations. The original Pentaxes have a wonderful, integrated feel to their operation. Film winding is delicious, the shutter release is positive, and it's like they said in the old advertisements, "just hold a Pentax". The S2-and-newer models are the most convenient to use, and their control layout is instantly familiar to anyone that has laid hands on a Spotmatic or K-series Pentax body. The three earliest models, with the slow speed dial, are desired by collectors, with the rare "S" or second-gen "Tower 26" (less than 5,000 produced) fetching the highest prices. The rare SB & SB2 Japanese military models are also valued by collectors. As far as a user body goes, our top recommendation is the SV/H3v. It had the benefit of all of the improvements made over during the first six years of Pentax production and possibly the coolest self-timer of all time :-). Over 480,000 were made, so they are fairly easy to come by, and prices are very reasonable. But any model from the S2 and up makes a great camera to build around. A couple of caveats: 1) the 1/1000 speed on the first-gen Pentaxes (and early Spotmatics, for that matter) seems to be more problematic than average. They can get a bit draggy and cause exposure issues. It's almost like Pentax had a good 1/500 shutter but they were pushing the design too hard at 1/1000. Because these bodies are at least 50 years old, a CLA (clean, lube, adjust) is often in order (especially when it comes to getting properly regulated shutter speeds), but just be aware that a CLA will not always cure a slow 1/1000 speed, and 2) the pre-Spotmatic Asahi Pentaxes do not seem to like cold weather, in general, and will often jam once their temperature threshold has been met. This is due to their fine tolerances combined with the lubricants' viscosity increasing. Other than that, the wonderfully sparse finder and mechanical excellence of these SLRs is a joy to experience. Just remember, you'll need a handheld or clip-on meter (make sure that your body has the machined cut-out in the shutter speed dial to allow the clip-on meter to couple), or you can just use Sunny 16, to get good exposures :-). 

   ​ Second Generation Mechanical Bodies

• 1964 - Pentax Spotmatic SP (aka Honeywell Pentax Spotmatic in US). In 1964, Pentax rocked the amateur SLR market with the introduction of its first integrated-meter model. The Spotmatic had been in development for five years (the prototype had been displayed at the 1960 Photokina). By the time it reached production, the spotmeter had been exchanged for an averaging one as Pentax felt that it would be more amateur-friendly. The DNA of the first-gen Pentaxes was very evident in the layout and form factor of the Spottie. Although the "R" on the rewind knob returned to the green color of the pre-'64 models, all Spotmatics were fully compatible with the 50/1.4 Super Takumar. The enclosed film counter of the SV shrunk a bit on the Spottie and, more importantly, the "T" setting on the shutter speed dial was eliminated, unfortunately. T is a nice alternative to using B (Bulb) in many situations, because it does not require a cable release to hold the shutter open. You simply press the shutter release to open the shutter, and it remains open until the shutter speed dial is turned to B, making long exposures a snap. "SP" was engraved on the top left shoulder of the Asahi version, but not on the Honeywell. The standard lens was the brand-new 50/1.4 Super Takumar, emphasizing the Spottie's position at the top of the Pentax lineup. The self-timer of the SV moved to the more-familiar position on the right-front panel of the camera. In 1968 a special order Spotmatic Motor Drive debuted. The motor drive will be described in greater detail in the Accessories section. They are quite rare and desirable to collectors. Nearly 1,788,000 SPs were produced. Body discontinued in 1974.

• 1968 - Pentax SL (aka Honeywell Pentax SL in the US). The meterless SL was the replacement for the SV in the SLR lineup. It was otherwise identical to the standard Spotmatic. It retained the slot in the shutter speed dial of the SV to allow the clip-on Meter II to couple with the camera. It was aimed at those photographers who still preferred to use a separate, handheld meter. "SL" was engraved on the top left shoulder of the camera for both Asahi and Honeywell versions. The standard kit lenses were the 55/1.8 and 50/1.4 Super Takumars, initially. Just over 136,000 built. Body discontinued in 1974.

• 1971 - Pentax Spotmatic II (aka Honeywell Pentax Spotmatic II in the US). This was the first improved Spotmatic model, with many internal changes, while maintaining an almost-identical appearance to its predecessor. The shutter, viewfinder, ISO range, self-timer, and film handling were all improved, with the most noticeable change being the inclusion of a fixed hot-shoe for flash on the slightly widened prism housing. The engraved model name now also featured "II" under the "SP" on the left shoulder of the body. The standard lenses were the new 50/1.4 and 55/1.8 Super-Multi-Coated Takumars. Over 478,000 produced. Body discontinued in 1973 (continued until 1977 in Japan only to use up existing parts supplies).

• 1971 - Honeywell Pentax Spotmatic IIa. This was a US-only version of the Spotmatic II that featured a built-in Strobo-Eye flash sensor for the Honeywell Strobonar flash system. Otherwise, it was identical to the Spotmatic II. Body discontinued in 1973. Estimated 22,000 produced.

• 1971 - Pentax SP500 (aka Honeywell Pentax SP500 in the US). This model was a flashback of sorts to the days of the S3/S1 by using a stripped-down version of the previous flagship Spotmatic to appeal to budget-conscious buyers. As the designation implies, top shutter speed was reduced to 1/500 sec. As well, the self-timer was deleted, and the 55/2 Super Takumar (notice: not Super-Multi-Coated) lens was standard. Just as on the previous S1 & S1a budget cameras, the detent for 1/1000 sec. on the shutter speed dial was still there and the shutter would fire at that setting, but it was not regulated by the high-speed cam mechanism of the SP. An estimated 150,000 were produced. Body discontinued in 1974.

• 1973 - Pentax Spotmatic F (aka Honeywell Pentax Spotmatic F in the US). With the introduction of the Super-Multi-Coated Takumars in 1971, Pentax had made provision for full or open-aperture metering. However, the Spotmatic II was not equipped to use this feature of such lenses as the Electro Spotmatic and ES models of 1971 were. That was rectified with the Spotmatic F. "F" was now engraved below "SP" on the top left shoulder of the camera. The Spotmatic F was the first and the final mechanical-shuttered Pentax to offer open-aperture metering. It was the top-of-the-line mechanical Spotmatic and offered full backward compatibility with all older Takumar lenses with stop-down metering. The standard kit lenses were the 50/1.4 and 55/1.8 SMC Takumars with their new rubber focus grips and restyled aperture rings. Production was approximately 604,000. Body discontinued in 1976.

• 1974 - Pentax SP1000 (aka Honeywell Pentax SP1000). This was the successor to the SP500. It was essentially an original Spotmatic with no self-timer. As implied by the model name, the top shutter speed of 1/1000 sec. was restored. Also the new kit lens, while retaining the 55/2 specification, now sported the SMC Takumar tag, meaning that it was now fully multi-coated. The SP1000 would prove to be the direct ancestor of the ubiquitous K1000 of 1977, which we will get to in Part 2 of this overview. Approximately 270,000 were made. The SP1000 would have the distinction of being the final M42 screwmount SLR produced by Pentax, being discontinued in 1977. 

    Recommendations. Mechanical Spotmatics have much to offer as learning tools or just enjoying the vintage SLR experience. They are simple, inexpensive, reliable, and are a gateway to an absolute avalanche of M42 lenses of all kinds and brands. The Spotmatic F sits at the top as far as features are concerned, and if full-aperture metering is a must for you, it's the only game in M42-town. A modern 357/SR44/S76 silver-oxide battery can be used with a 10mm (3/8") o-ring to power the meter. For all other mechanical Spotmatics, a silver-oxide 387S battery is the best option to power the meter (if you cannot get a 387, you can use a 394/380 cell with an 8mm (5/16") o-ring to achieve the same result). Spotmatics have a bridge circuit that automatically compensates for the voltage difference between the original mercury cell (1.35v) and the current silver-oxide battery (1.55), so the meter will work just fine as long as its calibration is on. Next comes the Spotmatic II with its integrated hot-shoe and internal improvements over the original Spottie. Another nice thing with most Spotties (except the Spotmatic F) is that there is an actual switch to shut off the meter. On the Spotmatic F (along with the K-mount bodies -  KM and K1000), you have to put the lens cap on to shut off the meter, which can sometimes be an inconvenience. Another advantage over the K1000 is the built-in DOF Auto/Manual lever on all Super Takumar and newer M42 Pentax lenses. So an SP1000, which other than the lens mount and meter switch is identical to the K1000, offers the DOF preview that the K1000 does not. There is nothing wrong with an SP500, but why lose out on 1/1000 sec. when a Spotmatic or SP1000 can be had so easily :-)? As noted above, carefully watch for draggy 1/1000 settings on mechanical Spotties of all ilks (same deal with KMs & K1000s, again in Part 2).

  Electronic Bodies

• 1971 - Pentax Electro Spotmatic. This was a landmark camera, being the first 35mm SLR with an electronically-controlled shutter and aperture-priority automation. It was exclusive to the Japanese market, and was really a prototype, as refinements were being made continually to the circuitry. It was also the first Pentax SLR to offer full-aperture metering with the simultaneously released Super-Multi-Coated Takumar lenses. Due to the location of the 544/PX28 battery used to power the camera, a self-timer was not included. Otherwise, the Electro Spotmatic was the highest-specified Pentax SLR. The shutter was an electro-mechanical hybrid, offering completely stepless (instead of being restricted to the discrete "steps" or numbers such as 1/250 the camera could select 1/235 or 1/463 or any other value in between) speeds from 8 to 1/1000 sec. in automatic mode, and mechanical speeds from 1/60 to 1/1000 + Bulb in manual mode. This meant that you would not be stuck with a useless camera if the battery died. However, when manual mode was engaged, the meter was disabled, a characteristic that would carry through with the two succeeding iterations. Make no mistake, Pentax intended these cameras to be used in Automatic unless the battery was dead :-). Exposure compensation was also introduced with this SLR, having a range of -1 to +2 EV. Another innovation that would eventually be adopted industry-wide was the activation of the meter by means of a half-press of the shutter release. A stop-down lever was included for backwards metering compatibility with older Super Takumars. The original Electro Spotmatics are more of a collector's item due to poor reliability with their nascent circuitry. Discontinued in 1971. Less than 2,500 produced. Serial numbers begin with 35xxxxx.

• 1971 - Pentax Electro Spotmatic/ES (aka Honeywell Pentax Electro Spotmatic in the US). The full-production version of the Electro Spotmatic debuted in late-1971. It contained improved circuitry, and as a result, was much tidier internally than the prototype above. The standard color was black for the electronic Spotties, as opposed to chrome for the mechanical bodies. Chrome copies are somewhat rare, but can be had occasionally for the same price as a black one. All basic specs and operations were identical to the prototype. During production there was a major modification to the circuitry of the camera to again improve reliability. This change was marked by a jump in serial number range from 55xxxxx to 65xxxxx and the elimination of the "Electro Spotmatic" script on the front of the camera in favor of a bold-type ES, making the 65xxxxx-numbered models the preferred option if you are in the market for one. Discontinued in 1973. Less than 150,000 produced.

• 1974 - Pentax ESII (aka Honeywell Pentax ESII in the US). Power consumption and the physical size of the camera's circuitry were reduced from that of the ES. Power was now supplied by 4 - 357/SR44/S76 cells relocated underneath the lens mount. This allowed for the inclusion of a self-timer. There was now a viewfinder blind setting on the shutter speed dial (only available in automatic mode) and the top ISO speed was expanded to 3200 from 1600 on the ES. The other new feature was the locking shutter release introduced on the Spotmatic F in the same year. This was a nice addition, as it prevented battery drain if the shutter release was inadvertently pressed in a camera bag. Interestingly, it was silver-colored, even on the black bodies. It could also be used to lock the shutter release open for extremely long exposures, as an informal sort of T (Time) setting. Remember, though, that the meter will be activated with the shutter release locked open, so it is wise to remove the batteries before performing long exposures using this feature. Serial numbers begin with 66xxxxx. Chrome ESII bodies were more common than with the ES model. Discontinued in 1976. Production just under 159,000.

    Recommendations. As alluded to above, the Electro Spotmatic is more noteworthy for its place in 35mm SLR history than as a great working camera for today. The ES was made more reliable (in two stages) and the ESII the best of the lot. The lack of metering in manual mode is a turn-off for many potential users. Functionally, these are beautiful cameras to use, with all of the classic Spottie ergonomics. Prices are generally very reasonable, but as with any vintage electronic body, ensure that the meter and shutter are fully functional before buying. The self-timer and viewfinder blind of the ESII add to its versatility. However, if those features are not a priority, a 65xxxxx-numbered ES can fit the bill, nicely.

  Flash

    Pentax had the earliest connections with electronic flash due to its relationship with Honeywell (and by extension, Heiland, who had worked with Harold Edgerton of MIT in his groundbreaking experiments in electronic stroboscopic photography in the 1930s & '40s). They featured Pentax SLRs in their advertising from the time that they became the US distributor for Asahi in the late '50s. Heiland was the market leader in flash technology from the 1940s through to the late 1960s. The Heiland Futuramic (1958) was the first self-contained electronic flash on the market. In 1965, now using the Honeywell name, they brought out the first auto-sensor electronic flash. There was a full line of flashes, from the off-camera "potato masher"-style units to compacts, and slaves for studio use. There were literally dozens of models offered throughout the era of M42-screwmount Pentaxes, although there were only 5 or 6 basic configurations. There was also a plethora of accessories to go along with the basic flash units themselves. Because Pentax used horizontal shutters in all of its production SLRs during the M42 period, maximum flash sync speed with electronic flash (X-sync) was 1/50 - 1/60 sec. 

    From the original Asahi Pentax (1957) until the arrival of the Spotmatic II (1971), Pentax SLRs did not have an integrated shoe for flash. There was an ISO "cold" shoe (no electrical connections, a PC cord had to be connected to the appropriate terminal on the camera) accessory that mounted to the viewfinder of the camera. If you want to mount a flash directly to any Pentax SLR from that era, you will need to get one of these detachable shoes. Back in the day, serious photographers often opted for off-camera flash via a mount bracket. This enabled them to use more powerful units while minimizing red-eye. It also made for a much sturdier setup.  

    You are by no means restricted to using Honeywell flash units, as there were a wide variety of aftermarket flash manufacturers and there was no worry about compatibility in those days. Flash was a manual job, with only a single X-sync contact or PC cord required. "Dedicated" (where the camera displays a flash-ready signal in the viewfinder) and TTL (through-the-lens metered) flash did not come to the Pentax system until the K-bayonet mount came along. So any manual or auto-sensor flash with a PC cord can be used with any pre-1971 M42 Pentax body. The Spotmatic II, F, Electo Spotmatic, ES, and ESII all have integrated hot shoes, for direct electrical flash sync without the use of a PC cord.

    Recommendations. As groundbreaking as the Honeywell flash system was in its day, there are some things to consider for the prospective user:

• Pre-thyristor units are battery-eaters. Thyristor circuitry permits the flash to only use as much power as is needed for proper exposure. Non-thyristor units dump the full charge of the flash capacitor, whether it is needed or not. It is wise to select a thyristor-equipped model regardless of the brand or system.
• Some Honeywell flashes utilized built-in nickel-cadmium batteries that required an AC adapter to be recharged. Others used replaceable ni-cad "C" cells that could be charged in place with an AC adapter. You may need some modest electrical skills to access and replace a built-in battery unit if necessary. Consider yourself warned ;-).
• Flash units (not just Honeywell's) produced well into the screwmount Pentax era tended to have higher trigger voltages than more modern ones. While this presents no problem with any of the Pentax cameras from the era, PLEASE make sure you that you ascertain the actual trigger voltage of any older flash if you have thoughts of also using it with a modern (late-'80s and newer) hot-shoe equipped camera. See the Photo Strobe Trigger Voltages site for a chart of many flash models and this page for a tutorial on how to measure them yourself. 

    There are definitely many options for flash with the Pentax screwmount system if you have the time and desire for manual flash. If you want more advanced features (like TTL) you will need to look elsewhere.

  Accessories

    When the Asahi Pentax debuted in 1957, there was a small selection of accessories that mostly centered on close-up and copy photography.  A copy stand, extension tubes, a bellows unit, and a microscope adapter ("adaptor" in the manual), along with a few filters and lens hoods were the extent of the lineup. By the time the S1 & S3 came along, a 90-degree viewfinder and a clip-on accessory shoe for external flash units had been added. Leather lens and camera cases also appeared about this time.   

    By the time the Spotmatic came around, a reverse adapter and a clip-on viewfinder magnifier had joined the party. For all of those budding, Pentax-packing private eyes, along with the Spotmatic II came a mirror adapter for the 200 & 300mm lenses that allowed the photographer to surreptitiously snap suspicious subjects while pointing the camera away from them. Seriously, we're not making this up. Somebody at Pentax must have been a '60s spy show addict ;-). On a less intriguing note, there was also a new helicoid extension tube that basically combined the function of the standard #2 and #3 tubes in an infinitely variable range of 16.8 to 30.6mm. 

    Motor Drives. Pentax introduced a motor drive option for the Spotmatic in 1968. Such models were special order and very rare. Considerable modification to the film transport and mirror assemblies was required. The top speed was 2.5 - 3.3 fps (frames per second) depending on shutter speed. Such cameras had "MOTOR DRIVE" engraved on the front or back edge of the bottom plate. The detachable drive unit had a centrally-mounted vertical battery grip underneath the motor housing. The original MD I (which was also used on the Spotmatic II) had three electrical contacts, while its successor, the MD II had four. The MD II (with matching Battery Grip II) was designed for use with the ES & ESII, and Spotmatic F bodies. A person must be very careful to match the proper drive unit to the particular camera body being used. A very helpful article can be found here at Asahi Optical Historical Club. The original Ni-cad batteries are nearly impossible to find nowadays (and therefore, are very expensive), but there was an adapter that allowed the use of 8 - alkaline AA cells (unfortunately, it is also very rare). Motor Drive units are basically a collectible due to their rarity and the scarcity of components available today. The Motor Drive-capable bodies retained a manual advance mechanism and can be used like any standard Spottie.

    Focusing Screens. Until the ES came along, there was no provision for using different focusing screens on a Pentax. The original screen was a matte field with a central microprism focusing aid. With the ES came the option of two other choices: a plain ground glass with central cross (for macrophotography), or a matte field with a central split-image rangefinder. These were not user-interchangeable; the camera had to be taken to a Pentax Service Center for the exchange to be made.

  Reliability & Servicing

    A major advantage of the M42 Pentaxes is their overall simplicity and they are easily serviced by any competent repairman. By the time the SV came on the scene, the basic design had been fettled to a high degree of refinement. Nevertheless, the Spotmatic was virtually all-new in its design. The rated shutter life rose very significantly to 100,000 exposures with the Spotmatic from the 20,000 of the SV and-earlier models. Brighter viewfinders, larger pressure-plates and film rails that improved film handling and flatness also were part and parcel with the Spotmatic. Constant, if minor improvements occurred well into the 1970s. The Spotmatic II brought more refinement to film handling. Parts bodies are generally plentiful and CLAs are among the least expensive of any vintage SLR. Sluggish high-speeds (1/125 - 1/1000 sec.) are the most common issue I have come across with the mechanical M42 Pentaxes. Most of the time this can be addressed with a CLA. One other thing to watch for is de-silvering of the pentaprism. This appears as grey or black smudges or lines in the viewfinder, and is generally the result of a body being stored on a hot, moist environment for long periods. The resulting fungal growth eats away the coating of the prism. It has no effect on photographs, it is merely an annoyance when composing and focusing. This can happen to any SLR; it is by no means exclusive to Pentax.

    When it comes to lenses, it is very tough to beat a Takumar when it comes to build quality and reliability. Many of these 40 - 60 year old lenses handle as if they came off the production line yesterday. The SMC coatings are very durable and the lenses themselves are easily serviced if necessary. They are truly one of the biggest draws of the M42 Pentax system. The other accessories were well built and will last for decades if properly cared for. 

  Conclusion

    The M42 Pentax system has much to recommend it as a viable vintage choice. Lenses and bodies can be had for very reasonable prices and build quality is excellent. Probably the biggest drawback is the screwmount itself. It takes 2 3/4 turns to secure a lens to a body, not the fastest procedure, and not even close to the convenience of a bayonet mount. But if you are not a compulsive lens changer, this may be something you can easily live with. If you just have to have a bayonet, don't despair...next up we will look at the Pentax K-mount in Part 2.

    Obviously, this article is merely an overview of the Pentax screwmount system. If you want to go further down this rabbit hole, I highly recommend Gerjan van Oosten's excellent book - The Definitive Asahi Pentax Collector's Guide 1952-1977 (2021). It is an updated version of his previous volume, The Ultimate Asahi Pentax Screw Mount Guide 1952-1977 (which, being long out of print - 1999, commands STUPID used prices). You get the benefits of two more decades of research and updates and for a fraction of the present cost of the older edition. You can purchase a copy directly from Mr. van Oosten at a very fair price via eBay (his Seller ID is garry-easton). It is a high-quality, 288-page, hardcover book. Be prepared for longer shipping times from the Netherlands, but the wait is well worth it :-).  

  References:

    Pentax Forums @ https://www.pentaxforums.com/camerareviews/
    The History of 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
    Radioactive Pentax Takumar Lenses
    The Definitive Asahi Pentax Collector's Guide 1952-1977 by Gerjan van Oosten