Leotax Leonon 5cm f/2

Leotax Leonon 5cm f/2

The Leotax Leonon 5cm f/2 is a Japanese LTM standard lens introduced in 1959 for the Leotax Elite rangefinder. It appeared near the end of Leotax camera production as a lower-cost alternative to standard lenses supplied by Tokyo Kogaku and Fuji Photo Film. Its Leica screw mount, mechanical rangefinder coupling and 50mm focal length make it fully relevant to LeicaLensList.

This entry covers the plain Leonon marked “LEONON 1:2 f=5cm” without an “S” suffix. A contemporary Leotax brochure identifies it as a six-element, five-group Gauss-type lens. It focuses to approximately 1 metre, accepts 40.5mm screw-in filters and has a ten-blade aperture closing to f/22. The barrel includes a chrome focusing lever but no infinity lock.

The pictured lens, serial number 230234, is an especially early plain Leonon. It falls slightly below the previously published observed range beginning around 23031x. Early examples are documented with ten curved aperture blades, while later plain Leonons generally use ten distinctively shaped or wavy blades.

Optical qualities

Rendering

Detailed controlled testing is limited, but repeated user comparisons describe the plain Leonon as having good central definition with lower microcontrast and weaker corner performance at wider apertures than the later Leonon-S. Its most consistently documented characteristic is strongly structured out-of-focus rendering rather than uniformly smooth blur.

Sharpness

Comparative testing indicates that the plain Leonon can be slightly sharper in the centre than the later Leonon-S, although the S version provides stronger microcontrast and better corner resolution at f/2. Results depend heavily on optical condition and accurate rangefinder calibration.

Bokeh and transitions

Out-of-focus highlights can show pronounced outlining and asymmetric brightness across the blur disc. Toward the edges, blur shapes become compressed and backgrounds can develop a busy or swirling appearance. The effect varies with subject distance, background structure and illumination, so it should not be expected in every photograph.

Contrast and flare resistance

The lens has coated optics, but no official coating name or specification has been confirmed. Contrast is generally lower than that of the later Leonon-S. Surviving examples with coating damage, haze or cleaning scratches may show substantially reduced contrast and increased flare.

Digital use

The lens can be used on Leica M cameras with an appropriate LTM-to-M adapter. Its mechanical rangefinder coupling should remain functional when the lens and adapter are correctly calibrated. It has no factory six-bit coding. Adaptation to mirrorless cameras is straightforward, but the approximately 1 metre minimum focusing distance remains unchanged unless a helicoid adapter is used.

History

Development and Launch

The plain Leonon was introduced as the standard lens for the later Leotax Elite, a version of the Leotax T2L rangefinder released in 1959. Earlier T2L cameras were commonly supplied with Topcor-S or Fujinon lenses, while the Elite name became associated with the more economical Leonon-equipped package.

Leotax was facing increasing competition from Canon, Nikon and the rapidly expanding Japanese SLR market. The Leonon therefore belongs to the final period of Japanese Leica-copy production, when manufacturers were attempting to reduce prices while retaining interchangeable LTM lenses and coupled rangefinders.

Production Evolution

Collector research records plain Leonon serial numbers mainly between approximately 23031x and 23371x. This suggests production of fewer than 4,000 lenses, but no official factory total has been located. The photographed serial number 230234 extends the currently documented lower end of that observed range.

Leotax entered bankruptcy proceedings in October 1959. Cameras and remaining components continued to be sold afterward, but the final manufacturing date of the plain Leonon is not confirmed. It was followed by Leonon-S lenses associated with the Elite S2 around 1960.

The actual optical manufacturer remains uncertain. Several Japanese sources attribute Leonon lenses to Showa Koki, a separate company from Leotax maker Shōwa Kōgaku, but surviving factory documentation has not conclusively established this attribution. The lens should therefore remain catalogued under its Leotax branding.

Special Editions/Variants

Three visibly distinct 5cm f/2 lenses carry the Leonon name. The plain Leonon covered here has no “S” suffix, normally carries a 23xxxx serial number and closes to f/22.

A scarce early Leonon-S resembles the contemporary aluminum-bodied Topcor-S and is generally found with serial numbers around 59xxxx. A second Leonon-S has a different stepped front bezel, normally carries a 34xxxx serial number and was supplied with the Leotax Elite S2. Both S versions close to f/16 and should receive separate LeicaLensList entries rather than being combined with the plain Leonon.

No commemorative, military or export-only edition of the plain Leonon is confirmed.

Collector Notes

The most reliable identification points are the absence of an “S” suffix, the “LEOTAX CAMERA CO., LTD.” front engraving, a 23xxxx serial number, f/22 minimum aperture and black barrel with chrome base and focusing lever. The lens accepts 40.5mm filters and does not have an infinity lock.

Some databases list the plain Leonon as a six-element, four-group lens. However, the Leotax brochure documented by specialist research describes the plain version as six elements in five groups. The six-element, four-group specification is more commonly associated with Topcor-S and later related designs.

Collectors should inspect the glass for haze, fungus, coating deterioration, fine scratches and separation. The aperture blades should be checked for oil, scuffing and smooth operation. Rangefinder calibration, focusing resistance and originality of the LTM mount are also important because lenses and camera bodies were frequently separated or exchanged.

Sources

• Leica Copies Japan, Leotax Rangefinder Cameras and Leonon Lens History
• Legacy Camera, The Leonon 5cm F2 from the Leotax Camera Company
• MFlenses, Leotax Leonon 5cm f/2 Plain and S Version Comparison
• Toby Marshall, Leotax Leonon 5cm f/2 Lens
• Kikuya Camera, Leotax Leonon 5cm f/2 Serial 230234

Special editions

No factory special editions or numerical product codes are confirmed. The two lenses marked Leonon-S are separate successor variants and should not be merged with this plain Leonon entry.