My interest in Pentax lenses should be obvious considering the articles on this website. One of the reasons I went down the rabbit hole of lens design history was to discover how the numerous lenses released by Asahi Optical related together over time. This article compiles the results of that research.
The format is original even if the lens data is available in numerous places. Read on to get a spreadsheet organised chronologically by lens family and optical design.
Updated 26 November 2024 to include some lens diagrams.
Constraints
I've restricted the scope to manual focus lenses released from 1957 to the end of the 1980s. By this time the first auto-focus line (Pentax F) was being marketed. I end here not because auto-focus lenses are bad -- indeed some are superb. But it's a given that the ease of manual focusing in AF lenses takes second place to the ease of motor-driven focus mechanisms. The ergonomics are simply not the same.
I've considered only normal primes of either 50mm and 55mm focal length. These conform to the heritage of symmetrical (double Gauss) designs I have recently documented. The 50mm macros and the pancake 40mm use different optical formulas.
My major contribution to the profusion of articles already extant is a chronological chart that groups similar lenses, so that it's easier to understand which models should operate and render similarly. Indeed, there is more similarity than difference in these lenses. Especially when used on digital bodies, where the aperture mechanisms are mostly irrelevant.
Why Pentax? They simply made some of the best lenses of the time, with a workmanship second to none. Indeed, I have several lenses from this list, now decades old, that still function perfectly despite never having been serviced. Few other manufacturers can make that claim. The ergonomics are also wonderful, with nicely damped rings and controls that fall readily to hand.
Aesthetically I prefer Leica and Zeiss lenses with their streamlined sleek looks. But Pentax are far from ugly, unlike other brands I won't mention for fear of offending!
It is an amazing fact that only three lens mounts have survived from the vintage days to the present. Two of those are described here: M42 and Pentax K. (The third is Nikon F.)
The chart
Please download the full chart as an ODS spreadsheet. This opens natively in LibreOffice or OpenOffice, but you can also use any other spreadsheet application you prefer.
Right-click, choose "save link as" or equivalent. If you get some guff about an insecure link, you will need to give permissions. It's not insecure, it's a normal HTTP link! Why is the internet so difficult these days? Oh right: corporations.
OK, here's a PDF version as well.
Lens lines
In 1952 Asahi Optical was the first Japanese company to release an SLR, following the German firms. The Asahiflex (1952-57) used M37 mount lenses with a convenient preset aperture. (Read my article that explains the different aperture mechanisms.)
In 1938 Carl Zeiss Jena developed the M42 screw mount. In 1949 the first M42 camera was introduced in East Germany. In 1957 the Asahi Pentax (AP) camera became the first Japanese M42 mount body. This was supported by a range of Takumar lenses. (The brand name was usually stylised in upper case). Asahi's use of this universal mount was so popular that M42 became known to many as the "Pentax thread mount".
Asahi Takumar lenses went through five different nomenclatures as features changed.
Takumar (1957-59) have manual or preset apertures. The Takumar 55mm F1.8 and 2.2 were standard primes included with the Asahi Pentax (AP).
Auto-Takumar (1958-63) added semi-automatic aperture control by way of a stop-down pin. You could stop down using a camera control which was coupled to the lens aperture.
Super-Takumar (1962-75) improved the coatings, though still single layer. Automatic aperture control was implemented through a stop-down pin (with M/A switch). In the "A" mode the camera would automatically stop down to the indicated aperture, returning to wide open for focusing and composition. With the release of the Asahi Pentax Spotmatic in 1964 the Super-Takumar 50mm F1.4 became the standard lens.
Super-Multi-Coated Takumar (1971-72) again improved the coatings.
SMC Takumar (1972-75) standardised the "SMC" naming that would be used in future Pentax brand lenses. The focus ring was now rubber.
In 1975 Asahi released the Pentax K camera and a new line of lenses using a proprietary bayonet mount of the same name.
SMC Pentax (1975-77) lenses aimed at the highest image quality and included the only Pentax collaboration with Zeiss. As a result these tended to be larger than other lines. Though it has no such designation, these are often called "Pentax-K" to distinguish from the others.
SMC Pentax-M (1977-84) lenses were designed at reduced sizes. A few models from the original line were not re-issued (e.g. the 50/1.2), so their retail life continued through the M period.
SMC Pentax-A (1984-89) lenses had a fully automatic aperture and communication that permitted new shooting modes on the Pentax Super Program. The lens designs were identical to the M series. Some parts were replaced with plastic for lighter weight. For this reason the "M" line are sometimes considered the pinnacle of this history, though there are naturally outliers in individual lenses.
SMC Pentax-FA (1991-) lenses were the first with auto-focus screw mechanisms. Some folks are not happy calling auto-focus lenses "vintage" but they are by definition. Though there have been several series since, several models have been kept in production, indicating their quality and popularity.
Optical families
This section groups extant lenses into families based on the optical design. Lenses in the same group can be considered optically similar, though other factors (metering method, coatings) will differ as already outlined. It is also true that lens materials and indices might have changed slightly between models, in various undocumented ways.
In practical terms, the performance you get from a particular lens will depend more on the history of use and abuse of that specimen than other factors. You can't depend on generalisations from other users but must test and use the lenses you have to determine the best fit for a given application.
For each family I share specifications in a compact format I devised. The numbers indicate: length / mass / close focus distance / filter thread / number of aperture blades. Numbers have been rounded off.
5 elements in 5 groups
This, the simplest lens formula, appears in two families. The first was the original Takumar. The second family were released as inexpensive options for buyers at the time.
- Takumar 55/2.2 (1957-59)
34mm / 155g / 55cm / 46mm / 10
Preset aperture.
- SMC Pentax-M 50/2 (1979-85)
- SMC Pentax-A 50/2 (1985-98)
31mm / 145-160g / 45cm / 49mm / 6
Open and automatic apertures respectively.
6 elements in 5 groups
There are six families with this improved optical formula. The first two use a 46mm filter thread and have the longer close focus distance characteristic of early Taks. Notice how lenses of different open apertures nonetheless use the same formula. This was a common marketing device: Asahi purposely limited the aperture of some lenses in order to sell them at a lower price, while saving costs on retooling a factory for a different build.
- Takumar 55/1.8 (1958)
- Auto-Takumar 55/2.2 (1961-63)
33mm / 165g / 55cm / 46mm / 10
Takumar is preset aperture; Auto-Takumar is manual aperture.
- Auto-Takumar 55/1.8 (1958-60) v1
- Auto-Takumar 55/2 (1958-59)
- Auto-Takumar 55/2.2 (1961)
33mm / 175g / 55cm / 46mm / 10
Semi-auto aperture.
- Auto-Takumar 55/1.8 (1960-62) v2
- Super-Takumar 55/1.8 (1962-65) three variants
- Super-Takumar 55/2 (1962-73)
36mm / 165-215g / 45cm / 49mm / 6
Auto aperture. Auto-Takumar is the heaviest.
- Super-Multi-Coated Takumar 55/1.8 (1971-72)
- SMC Takumar 55/1.8 (1972-75)
- SMC Takumar 55/2 (1973-75)
38mm / 200-215g / 45cm / 49mm / 6
Super-Multi-Coated Tak is auto aperture; others open aperture.
- SMC Pentax 55/1.8 (1975-77)
- SMC Pentax 55/2 (1976-77)
39mm / 220g / 45cm / 52mm / 6
- SMC Pentax-M 50/1.7 (1977-83)
- SMC Pentax-A 50/1.7 (1983-89)
31mm / 185g / 45cm / 49mm / 6
The smallest and lightest of this optical family.
A lens diagram for this configuration follows. This conforms to the Pentax-M 50/1.7 but is also found in US patent 3,817,603 here. This dates back to 24 May 1971 and is credited to Yasuo Takahashi.
8 elements in 6 groups
Only a single model was made with this extravagant formula. This was quickly replaced as the production cost was too high.
- Super-Takumar 50/1.4 (1964-65)
43mm / 245g / 45cm / 49mm / 6
7 elements in 6 groups
This optical formula range began with the replacement for the famed 8-element Tak (above). This adds one final element to the 6 in 5 design, for further aberration correction.
- Super-Takumar 50/1.4 (1965-71)
38mm / 230g / 45cm / 49mm / 6
- Super-Multi-Coated Takumar 50/1.4 (1971-72)
- SMC Takumar 50/1.4 (1972-75)
41mm / 230-250g / 45cm / 49mm / 8
- SMC Pentax 50/1.4 (1975-77)
42mm / 265g / 45cm / 52mm / 8
The original K range was unusually large for Pentax. Note the filter size.
- SMC Pentax-M 50/1.4 (1977-83)
- SMC Pentax-A 50/1.4 (1983-89)
37mm / 240g / 45cm / 49mm / 8
Notably larger than the f/1.7 variants, but not huge by any means.
- SMC Pentax-FA 43/1.9 Limited (1997-2021)
27mm / 155g / 45cm / 49mm / 8
The smallest of all such primes and the only one at 43mm focal length, the exact diameter of the 135 film frame. I include this because it is a distinctive lens that nonetheless follows the classic 7 in 6 formula.
Here I compare a famed Carl Zeiss diagram with those discussed above. The similarities are evident, even across designers and several decades of production.
7 elements in 6 groups (modified)
Some of the lens elements have a different shape from the family above. No double necessary to get to that maximum aperture. The Pentax-A variant changes the aperture blade count, the only such case in the Pentax line.
- SMC Pentax 50/1.2 (1975-83)
49mm / 345g / 45cm / 52mm / 8 - SMC Pentax-A 50/1.2 (1983-2004)
49mm / 345g / 45cm / 52mm / 9
Which to choose?
Generally the newest lens in each category is the best buy for several reasons. First, it will have the benefits of all incremental improvements (to coatings, etc.). Second, the specimen will simply not be as old and so less likely to have issues. Third, it will likely be more compact than earlier designs. Finally, it's likely to be cheaper than rarer and more collectable old models.
I am pragmatic, so I own the SMC Pentax-M 50/1.7 for daily photos (starting at f/2.8) and the SMC Pentax 50/1.2 for speed. But I never use the second lens because soft photos and aberrations are not my cup of tea.
In decades of practice, I've seen no evidence that a Takumar would improve my photos in any way. However, some people just prefer an older lens for the feeling it gives them. I'm not knocking that!
References
I've compiled the information here over several decades from many sources: Pentax Forums (including the Lens Review section), defunct newsgroups, scans of manuals and brochures, etc.
For this article I've double-checked the data with Evgenii Artemov's LENS-DB, which can be considered authoritative.
Corrections are welcome, especially if you can find further patents and discover designer credits.
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