Kowa Prominar 100mm f/2

Kowa Prominar 100mm f/2

The Kowa Prominar 100mm f/2 is a rare Japanese short telephoto produced by Kowa Optical Works for Leica thread-mount rangefinder cameras. Its fast aperture and original rangefinder-coupled M39 barrel make it a distinctive portrait lens from the post-war Japanese optical industry.

Optical Qualities

The lens uses six elements in three groups. The 100mm focal length provides a compressed perspective suitable for portraits and detail work, while the f/2 maximum aperture allows selective focus and low-light use. Rendering can vary with the condition of surviving examples, particularly because these lenses are now several decades old.

History

Kowa Optical Works produced the Prominar 100mm f/2 during the 1950s, with published lens references placing the model around 1957. It belongs to the small group of fast Japanese telephoto lenses made in Leica-compatible screw mount during the expansion of Japan's post-war camera industry. Original M39 examples are uncommon.

Handling

The lens focuses to approximately 1.5 metres and accepts 55mm filters. Its substantial metal barrel reflects the construction typical of fast telephoto lenses of the period. An external finder is useful for accurate framing on Leica screw-mount cameras without 100mm framelines.

Compatibility

Original examples use the Leica thread mount, also known as LTM or M39, and include mechanical rangefinder coupling. They can be used on compatible screw-mount rangefinders and on Leica M bodies with a suitable LTM-to-M adapter.

Sources

• Leitz Photographica Auction, Kowa Optical Works Japan Prominar 2/100mm
• LENS-DB, 90 to 100mm rangefinder lens comparison table