Glass Bodies a variant-level encyclopedia of vintage lenses and cameras by iwillpat

Komura 105mm f/2

Sankyo Koki · Nikon S + LTM · 1960 · Ernostar

Also known as: Komura- 105mm f/2 · Komura 105mm F2 · Sankyo Koki Komura 105mm f/2 · Sankyo Kohki Komura 105mm F/2 · 三協光機 KOMURA 105mm F2 · コムラー 105mm F2

Variants & identification

Variant Mount Years Serial ranges Production
Nikon S Nikon S — 4350088 (photographed example) —
Leica screw mount LTM 1960–1967 — —
  1. Sankyo Koki published no production figures for any of its rangefinder lenses, and no S-mount price list survives.
How to tell them apart (expand)
  • Tell apart from the 105mm f/2.8 sibling by filter size and blade count: the f/2 takes 58mm filters with 12 blades, the f/2.8 48mm with 16
  • The later 105mm f/2.5 shares the optical design (1m close focus vs 1.5m) but exists only in SLR/Unidapter fittings — never in Nikon S mount

Nikon S:

  • Nikon-mount Komuras carry an 'N' barrel marking, though some late lenses are unmarked
  • Front bezel reads KOMURA- f=105mm 1:2 No.xxxxxxx Sankyo Koki Japan

Serial-range notes

4350088
Photographed Nikon-mount example.

Specifications

Formula
Ernostar
Construction
5 elements / 4 groups
Aperture range
f/2–f/16
Diaphragm blades
12
Min. focus
1.5 m
Filter
58 mm
Years manufactured
1960
Country
Japan
Original price
$120 (LTM) (today $1,200) — the 1965 EPOI list covers the screw-mount and SLR lines only; no S-mount Komura price list has ever surfaced

What reviewers say

Optical Ratings

Aggregated from the reviews above — follow the links for the full picture.

Spherical aberration
soft wide open
Coma
swirly bokeh
Optical formula — Ernostar
Deliberately a schematic, drawn from the formula type rather than a published diagram (Camera-wiki's Komura 105mm f/2.0 page confirms 5e/4g and Ernostar lineage ('king of Ernostar') and references a lens diagram (1963 Komura catalogue diagrams are reported to exist), but I could not fetch the diagram itsel); topology as the type implies, curvatures stylized.
Deliberately a schematic, drawn from the formula type rather than a published diagram (Camera-wiki's Komura 105mm f/2.0 page confirms 5e/4g and Ernostar lineage ('king of Ernostar') and references a lens diagram (1963 Komura catalogue diagrams are reported to exist), but I could not fetch the diagram itsel); topology as the type implies, curvatures stylized. — Drawn for this site, CC BY 4.0

History

On Western message boards the Komura 105mm f/2 goes by the nickname “King of Ernostars” — a five-element, four-group telephoto in the lineage Ludwig Bertele laid down in the 1920s, and the fastest 105 ever offered for the Nikon rangefinder, out-speeding Nikon’s own celebrated Nikkor-P·C 10.5cm f/2.5. It arrived around 1960 as a late addition to Komura’s Nikon-mount line, and it is rare enough in S mount that its existence there rests on surviving examples rather than any catalog — anchored by a Japanese collector’s first-hand account of his own Nikon S example.

Sankyo Koki was founded in 1951 and sold lenses under the Komura brand from 1955; the company lasted until 1980. Its Nikon-mount line ran from the late 1950s into the early 1960s, following the same convention as Tanaka’s Tanar lenses: an “N” marking on the barrel identified the Nikon fit, though some late lenses went unmarked. The initial S-mount range consisted of four lenses — a 35mm f/2.8, an 80mm f/1.8, a 105mm f/2.8, and a 135mm f/3.5 — with the 105mm f/2 among a handful of later additions that arrived as the rangefinder era was already winding down.

The lens itself pairs its Ernostar formula with a preset 12-blade aperture, a 58mm filter thread, and a 1.5-metre minimum focus. Japanese literature dates the Leica-screw version to 1960, on sale until 1967, and the known Nikon S example dates to around the same year, weighing in near 440g. In use it behaves like the classic large-aperture Ernostar it is: soft wide open, tightening up between f/2.8 and f/4, with background bokeh that goes distinctly swirly at f/2 — the verdict of the collector whose example confirms the mount.

The paper trail is thin. No production quantities are documented anywhere for Sankyo Koki’s rangefinder lenses, and no S-mount price list survives; the only surviving original price is American — $120 for the Leica-screw version on the 1965 EPOI list. One caution for collectors: the later Komura 105mm f/2.5 shares this lens’s optical design and improves the close focus to 1 metre, but no source places it in S mount — it belongs to the SLR/Unidapter era — so the f/2 stands as the end of the line for the fast Komura 105 on the rangefinder.

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This history is AI-written, from the sources listed at the foot of the page. Where the record is silent it says so rather than filling the gap — but no human wrote these sentences.

Example photos

More sample photos elsewhere

These photographers keep all rights to their work — enjoy it at the source.

Sample photo wanted — shot with a Komura 105mm f/2? We'd love to feature it (with credit).

Live listings

Asking price, USD: a median of $350 across 14 fixed-price listings on 2026-09-06 (middle half $250–$370). First day tracked.

Asking prices from the listings scanned, not sales; junk-flagged rows and auction lots excluded; other currencies are not converted.

Show 6 more listings

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Listings updated 2026-09-05. Links go to the shop or marketplace that carries the item.

Related: Komura 105mm f/2.8 · Komura 135mm f/2.8 · Nikkor-P·C 10.5cm f/2.5

Sources (7)

Every page here is assembled from public sources, and the gaps are real ones. If you own this lens, know a serial number I'm missing, or can see where I have it wrong, tell me — corrections, serials and sample photos are all worth having.