Takumar 50mm F1.4 is a fast prime lens introduced by Asahi optical Co. (Pentax) from 1965 to 1975 in two "Super" versions as well as two versions with Super-Multi-Coating.

Figure-1 produced in the late stage of 1972-1975, 7 elements ver

The label of some early stage SMC lenses is Multi-Coated Super-Takumar.

The Super-Takumar made in early 1964 had 8 elements and other variants only have 7 elements.

The 7 element Takumars have the infrared focusing mark to the left of the numeral '4' on the DOF scale. The 8 element version has the mark to the right.

Super-Takumar 1:1.4/50, late model. Some have a white dot on the aperture ring at the f/2 position.

Figure-3 1965-1971 late model

Figure-4 parameter of early model without SMC

Figure-6 parameter of late model with SMC

This lens is very interesting. Its first element used the Thorium to enhance its optical capability while the Thorium is radioactive and this glass will become yellow after long term use. Another point is its advanced SMC technology which driving a storm in the 1970s. Zeiss introduced T* coating at that time to take part in the battle.

Radioactive

Nowadays, manufactures usually adds lanthanum (La) dioxide into glass to increase its refractive index and decrease dispersion. But at that time, the glass makers chose the thorium (Th) dioxide.

All known thorium isotopes are unstable. The most stable isotope, 232Th, has a half-life of 14.05 billion years, or about the age of the universe; it decays very slowly via alpha decay, starting a decay chain named the thorium series that ends at stable 208Pb. On Earth, thorium and uranium are the only significantly radioactive elements that still occur naturally in large quantities as primordial elements.

Because of its very long term half-life, the radiation amount in certain period is at very low level. The alpha particles cannot penetrate skin and very thin paper. Unless eating or breathing it into body, its radiation is weaker than the background radiation.

When added to glass, thorium dioxide helps increase its refractive index and decrease dispersion. Such glass finds application in high-quality lenses for cameras and scientific instruments. The radiation from these lenses can darken them and turn them yellow over a period of years and it degrades film, but the health risks are minimal. Yellowed lenses may be restored to their original colourless state by lengthy exposure to intense ultraviolet radiation.

Recover video from youtube

Figure-7 yellowed lens (left)

But there are also people treat it as a kind of stylish yellow filter.

Thorium tetrafluoride is used as an anti-reflection material in multilayered optical coatings. It is transparent to electromagnetic waves having wavelengths in the range of 0.350–12 µm, a range that includes near ultraviolet, visible and mid infrared light. Its radiation is primarily due to alpha particles, which can be easily stopped by a thin cover layer of another material.

SMC - the advanced coating technology

In 1971, Asahi Optical Co,.made an innovative advancement in optical technology by increasing the number of coating layers from two — the norm at the time — to as many as seven. They named this multi layers coating technology SMC short for "Super Multi Coating".

When Asahi Opt. Co. (PENTAX) introduced their Super-Multi-Coated Takumar lenses in 1971, there were many different reactions to this announcement. The coating layers of SMC was 7 and common caoting layers was 2 at that time. According to an article authored by Fabio Amodeo and published in September of 1972 by Photo 13 magazine, Nikon stated that they already employed multi-layer coatings (up to three or four) on some lens surfaces and Asahi was fooling photographers, since no more than 5 layers were technically possible. Also Canon and Leitz said they were developing a similar process, but 7 layers was far from being credible. To the contrary, Fuji said they were ahead, since they already had developed their own EBC (electron-beam coating) technology up to 11 layers, employed on some lenses for movie cameras on occasion of 1964 Olympic Games. Further in reaction of the Asahi announcement, Fuji said they were going to use EBC on camera lenses very soon.

Figure-9 sample photo taken by SMC lens. Image from Fotografare magzine published in 1974

Asahi did not invent the multicoating, since they bought patents from Optical Coatings Laboratories Inc. (OCLI), based in California. The merit of Asahi Opt. Co. was to understand the importance of anti-reflective coating, looking for the proper technology, developing their own industrial process and put it into production at acceptable costs.

It is believed that nearly all major lens makers (including Canon, Nikon and Zeiss) paid royalties to Asahi to make use of some part of the industrial process for laying thin anti-reflective compounds on glass elements at acceptable costs. Leica obviously distinguished itself by stating that multicoating was of little help and reducing the number of elements was better for flare control. Of course, when Asahi patents on multicoating expired many years later, they suddenly changed their minds and started using multicoating like all other manufacturers.

T* coating (Transparent) was introduced by Zeiss in 1972 to compete with Pentax SMC. T* is also advanced multi layers coating technology invented by Zeiss independently.

The photo magazine at that time had done flare tests for these lens and published in the Fotografare in 1974. Please note that the focal length and aperture will affect the test result. We only need to pay attention to the lenses of 50/1.4 type.

Figure-10 Flare comparison from Fotografare in 1974

From the table we can see that the percent flare of Super-Takumar without SMC is 0.9. SMC Takumar is 0.47 compared with 0.9 of Leica Summilux, 0.88 of Cannon FD, 0.93 of Nikon Nikkor-S, 1.04 of Fuji EBC Fujinon. The performance of SMC is really outstanding at that time.

In 2012, Pentax introduced the new HD Coating technology. It forms an eight-layer coating with a uniform layer thickness, created by a high-precision, ion-assisted evaporation process. This is further reinforced by a ninth coating added to the outermost layer by a vacuum evaporation process. The HD coating is high-performance, cost-efficient and used in modern lenses.

About Pentax Company

The company was founded as Asahi Kogaku Goshi Kaisha in November 1919 in Tokyo.

In 1938 it changed its name to Asahi Optical Co., Ltd.which is commenly used on lens labels.

Since Asahi Optical devoted much of its time to fulfilling military contracts for optical instruments during WWII. At the end of the war, Asahi Optical was disbanded and then being allowed to re-form in 1948. The company resumed its pre-war activities, manufacturing binoculars and consumer camera lenses for Konishiroku and Chiyoda Kōgaku Seikō (later Konica and Minolta respectively).

The Korean War saw a huge influx of journalists and photographers to the Far East, where they were impressed by lenses from companies such as Nikon and Canon for their Leica rangefinder cameras, and also by bodies by these and other companies to supplement and replace the Leica and Contax cameras they were using.

In 1952 Asahi Optical introduced its first camera as well as the first Japanese 35 mm SLR - the Asahiflex.

Figure-11 Asahiflex

The name "Pentax" was originally a registered trademark of the East German VEB Zeiss Ikon (from "Pentaprism" and "Contax") and acquired by the Asahi Optical company in 1957.

Since then the company has been primarily known for its photographic products, distributed 35mm equipment under the name "Asahi Pentax" and medium format 120 6x7cm equipment under the sub brand "Pentax 6x7" (from 1969 to 1990) and "Pentax 67" (from 1990 to 1999).

Equipment was exported to the United States from the 1950s until the mid-1970s by Honeywell Corporation and branded as "Heiland Pentax" and later "Honeywell Pentax".

The company was renamed Pentax Corporation in 2002.

In 2006, Pentax started the process of merging with Hoya Corporation to form 'Hoya Pentax HD Corporation', but failed.

In 2007, Hoya completed a friendly public tender offer for Pentax and acquired 90.59% of the company. Then the company became a consolidated subsidiary of Hoya.

In 2011, Hoya sell its Pentax camera business to Ricoh. The company was renamed the new subsidiary Pentax Ricoh Imaging Company, Ltd. Hoya will continue to use the Pentax brand name for their medical related products such as endoscopes.

In 2013, the company name was changed to Ricoh Imaging Company Ltd. The Pentax company comes to end.

Samples

NONS SL42 + SMC Takumar 50/1.4

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