55mm f/1.8 Pentax prime with mildly radioactive glass elements — produces warm yellow casts and soft contrast, ideal for vintage or retro looks.
Technical Details
The lens consists of 6 elements in 4 groups and achieves a minimum focusing distance of 45 cm. The aperture ranges from f/1.8 to f/16 with 6 aperture blades, and the filter diameter is 49mm. Early versions (1964-1971) contain radioactive thorium oxide in the glass elements, contributing to the characteristic warm, slightly yellowish rendering and causing the lenses to discolor to amber over time. Later SMC (Super Multi Coating) versions from 1971 onwards omitted thorium and introduced multi-layer coating. The lens weighs 225g and has a length of 43mm.
History & Development
Asahi Optical introduced the Takumar series in 1957, followed by the Super Takumar 55mm in 1964 as an evolution of the Auto Takumar. The thorium-containing versions were produced until 1971, when environmental concerns led to the SMC version without radioactive elements. In 1975, the SMC Pentax-M 50mm f/1.7 replaced the 55mm focal length as the new standard. Production ended with the introduction of the K-mount, which replaced the M42 screw mount.
Practical Use in Film
The Super Takumar 55mm has experienced a renaissance in digital filmmaking due to its organic image quality and characteristic bokeh. Indie filmmakers appreciate the soft rendering at wide apertures and the vintage look of the thorium-containing versions. When used on modern digital cameras via M42 adapters, it produces natural depth of field with creamy backgrounds at f/1.8. Manual focusing requires precise work but rewards with an authentic analog feel. It is particularly valued for portraits and available light scenes.
Comparison & Alternatives
Compared to modern autofocus lenses, the Super Takumar offers less sharpness at wide apertures but more characterful rendering. The contemporary Carl Zeiss Pancolar 50mm f/1.8 achieves higher resolution, while the Super Takumar delivers warmer colors. Modern alternatives like the Pentax FA 50mm f/1.4 or Sigma 50mm f/1.4 Art offer technical superiority but cannot replicate the vintage rendering. Collector prices for thorium-containing copies range from 150-300 Euros, while SMC versions cost 80-150 Euros.