Angénieux Type S1 50mm f/1.8

P. Angénieux Type S1 50mm f/1.8

The P. Angénieux Type S1 50mm f/1.8 is an early high-speed French standard lens based on a six-element, four-group Double Gauss design. It was produced for several camera systems, including exceptionally rare factory rangefinder versions in Leica Thread Mount and Contax RF mount.

Original LTM examples use a complete Angénieux focusing barrel and are rangefinder coupled. Original Contax examples use the external bayonet and their own focusing assembly. These are factory-produced mount variants of the same S1 lens, not later adaptations, and both are therefore covered by this profile.

Two documented lenses provide especially strong evidence for this relationship. A Contax example carries serial number 160746, while an original rangefinder-coupled M39 example carries serial number 160767. The nearly consecutive numbers support their treatment as parallel factory versions of the same optical model.

The physical specifications currently associated with the profile, including the approximately 110g weight of some aluminium examples, describe documented LTM lenses. They should not automatically be applied to the Contax barrel.

Optical qualities

Rendering

The Type S1 has a comparatively gentle image at f/1.8, with moderate contrast and reduced fine-detail definition away from the centre. Stopping down increases contrast, definition and overall uniformity.

Bokeh and transitions

The combination of a 50mm focal length and f/1.8 aperture provides substantial background separation. The Double Gauss design produces a recognisably vintage transition from focused to unfocused areas, although the exact appearance varies with aperture, optical condition and individual production version.

Contrast and coating

Both uncoated and coated examples are documented. Early coated lenses can show pale blue reflections, while later coatings may appear more strongly blue or purple. Coating type has a noticeable influence on flare resistance and contrast.

Flare and aberrations

Uncoated and lightly coated examples can lose contrast rapidly in strong backlighting. At maximum aperture, glow, spherical aberration and reduced edge definition may be visible. These characteristics improve when the lens is stopped down.

No verified optical distinction has been established between the original LTM and Contax RF versions.

History

Development and Launch

The Type S1 belongs to Angénieux's early S-series of high-speed photographic lenses. The design appeared during the 1940s and was manufactured for several European camera systems.

Factory LTM and Contax RF examples are both documented. Auction dating for surviving lenses is not completely consistent, even for nearly consecutive serial numbers, so exact manufacturing years should be treated cautiously unless supported by additional factory records.

Production Evolution

The Type S1 appeared in several mounts and barrel configurations. Original rangefinder versions were produced alongside lenses for Alpa, Rectaflex, Exakta and other systems.

Some Alpa lenses carry the Alitar name. These share the broader S1 optical family but are not automatically original Leica or Contax rangefinder lenses. Modern specialists have converted optical heads from these other systems into Leica M and M39 focusing mounts.

Coating was introduced gradually. Surviving lenses with close serial numbers can differ in coating, suggesting that coated and uncoated production overlapped.

Collector Notes

Originality of the focusing mount is critical. A genuine factory LTM or Contax RF lens should be distinguished from an S1 optical head later fitted to a modern rangefinder mount.

Collectors should inspect for balsam separation, haze, coating wear and cleaning marks. Separation is regularly encountered in surviving S1 lenses and can significantly reduce contrast.

The mount-specific focusing mechanism, engravings, serial number and overall construction should be documented whenever possible.

Special editions

No factory special edition with a separate model or catalogue number is confirmed. Uncoated lenses, pale-blue-coated lenses and the different factory mounts are production variants. Alitar-marked lenses belong to a related factory application and should not be listed as a special edition of the rangefinder S1.