Nippon-Kogaku Nikkor-P.C 10.5cm f/2.5

Nippon Kogaku Nikkor-P.C 10.5cm f/2.5

The Nippon Kogaku Nikkor-P.C 10.5cm f/2.5 is a fast Japanese telephoto lens produced for rangefinder cameras, including examples in Leica L39 / LTM / M39 screw mount. It was designed by Zenji Wakimoto and became one of the most important early Nikkor telephoto lenses. Nikon records that the optical design was completed in 1949, with mass-production preparations announced in 1953 and the lens released near the end of summer 1954 [1].

The lens is usually engraved Nikkor-P.C 1:2.5 f=10.5cm. In Nippon Kogaku’s naming system, the letter P indicates a five-element optical construction, while C identifies a coated lens. Nikon confirms a Sonnar-type formula consisting of five elements in three groups [1].

This entry covers factory-made Leica screw-mount versions. The lens was also produced for Nikon S and Contax-compatible rangefinder mounts, which should not be connected to this entry unless the physical lens has the Leica L39 screw mount. A 105mm optical finder, hood, case or L39-to-M adapter should be recorded as an accessory rather than as part of the model name.

Optical qualities

Rendering

The Nikkor-P.C 10.5cm f/2.5 was designed with portrait and close-distance rendering in mind. Nikon describes its optical correction as deliberately retaining some under-corrected spherical aberration, producing gentler rendering and attractive background blur rather than maximizing clinical sharpness alone [1].

Sharpness

At f/2.5, the lens provides good resolution across much of the frame, although slight flare and inner coma may soften the central image character. Nikon reports improved central sharpness between approximately f/2.8 and f/4, with more consistent performance across the frame around f/5.6 to f/8 [1].

Contrast and color

The coated Nikkor-P.C generally offers better contrast than comparable uncoated prewar telephoto lenses. Its contrast remains more moderate than that of later multicoated lenses, helping preserve tonal transitions on film. Optical haze, coating damage and internal reflections can significantly reduce contrast in surviving examples.

Bokeh and transitions

The combination of a 105mm focal length, f/2.5 maximum aperture and Sonnar-type optical construction produces substantial subject separation. Nikon specifically notes that the lens’s spherical-aberration correction contributes to natural and pleasing background blur [1].

Distortion and vignetting

Nikon measured distortion at approximately 0.5 percent, a relatively low figure for an asymmetrical Sonnar-type telephoto design [1]. Independent practical testing indicates that noticeable vignetting can occur at full aperture and reduces considerably when stopped down [2].

Handling

The Leica screw-mount version is rangefinder-coupled and focuses to approximately 1.2 metres. The long focusing throw allows precise adjustment but can feel slower than that of smaller normal lenses. A separate 105mm finder is useful on cameras without suitable framelines.

The lens accepts 52mm filters. Some examples were sold together with a dedicated finder, hood, caps and leather case. These accessories can add collector value but do not identify a separate optical version.

Digital use

The lens can be fitted to Leica M bodies with an L39-to-M adapter. Because the narrow rangefinder cam used on some examples may not engage equally well with every third-party adapter, accurate rangefinder operation should be checked on the intended body [3]. It can also be adapted to mirrorless cameras for direct live-view focusing.

History

Development and Launch

Zenji Wakimoto completed the design in 1949 after his work on improvements to the Nikkor-P.C 8.5cm f/2. Nikon released the 10.5cm f/2.5 in 1954, when it was among the fastest lenses available in the 100mm focal-length class [1].

The 105mm focal length filled the gap between common 85mm portrait lenses and longer 135mm telephotos. Its popularity helped establish 105mm as one of Nikon’s characteristic portrait focal lengths.

Production Evolution

Rangefinder versions were produced in Leica screw, Nikon S and Contax-compatible mounts. The optical unit remained closely related across these rangefinder versions, while the focusing mounts and coupling mechanisms differed.

At least two minor rangefinder barrel variations are documented. Early examples used small lugs for attaching the hood, while later examples used a smoother front-barrel arrangement. These are minor mechanical differences and do not require separate lens entries [2].

The original 5/3 Sonnar-type concept was later adapted for the early Nikon F-mount 105mm f/2.5. Nikon modified the rear optical element slightly to provide the extra clearance required by an SLR mirror, while retaining essentially the same aberration balance [1].

Special Editions/Variants

No commemorative factory special edition is documented. Collector-relevant differences include:

• Nippon Kogaku Tokyo versus Nippon Kogaku Japan engraving
• Leica L39, Nikon S and Contax-compatible mounts
• Earlier and later hood-mounting barrel details
• Feet-only or combined metres-and-feet focusing scales
• Included 105mm finder, hood, caps and leather case

These details should be recorded per copy but do not normally justify separate optical entries.

Collector Notes

Collectors should verify the front-ring engraving, 10.5cm f/2.5 marking, Leica screw mount, rangefinder cam, focusing scale and serial number. Important condition checks include internal haze, fungus, cleaning marks, coating damage, oily aperture blades, stiff focusing and damage to the long barrel or tripod mount.

The Leica screw-mount version should not be confused with the visually similar Nikon S-mount version. The rear mount and rangefinder coupling must be inspected rather than relying solely on the front-ring name.

Special editions

No confirmed factory commemorative special edition is documented.

Known collector-relevant versions and related lenses include:

• Nikkor-P.C 10.5cm f/2.5 in Leica L39 / LTM / M39 screw mount, this entry.
• Nikkor-P.C 10.5cm f/2.5 in Nikon S mount, separate mount version.
• Nikkor-P.C 10.5cm f/2.5 in Contax-compatible rangefinder mount, separate mount version.
• Early rangefinder examples with hood-retaining lugs.
• Later rangefinder examples with a smoother front-barrel hood fitting.
• Examples supplied with a dedicated 105mm optical finder, hood, caps and leather case.
• Nikkor-T 10.5cm f/4, a slower and optically separate lens.
• Nikkor-P Auto 10.5cm f/2.5 for Nikon F mount, related successor but not this rangefinder entry.
• Later 105mm f/2.5 AI and AI-S lenses, optically and mechanically separate SLR versions.

Sources

• [1] Nikon Imaging. NIKKOR, The Thousand and One Nights No.45: The NIKKOR-P.C 10.5cm f/2.5. https://imaging.nikon.com/imaging/information/story/0045/index.html
• [2] Richard Haw. Repair: Nikkor-P.C 10.5cm f/2.5. https://richardhaw.com/2017/06/18/repair-rf-nikkor-p-105mm-f2-5/
• [3] Rangefinderforum. Nikon 105mm f/2.5 L39 disassembly and coupling discussion. https://rangefinderforum.com/threads/nikon-105mm-f2-5-l39-disassembly.4815412/
• [4] MIR. Nikon RF Nikkor 105mm lenses. https://www.mir.com.my/rb/photography/companies/nikon/nikkoresources/RF-Nikkor/RF105mm/index.htm
• [5] Emulsive. 5 Frames with the Nikon Nikkor-P.C 10.5cm f/2.5 LTM. https://emulsive.org/articles/5-frames-with-the-curious-nikon-nikkor-p-c-10-5-cm-f-2-5-ltm-on-adox-silvermax-100-35mm-format-ei-100-leica-m7-by-jose-mendes-de-almeida