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

Mamiya-Sekor C 55mm f/2.8 (645)

Mamiya · Mamiya 645 · 1975

single source, unconfirmed

Also known as: Mamiya-Sekor C 55mm f/2.8 · Mamiya Sekor C 55mm f2.8 · Mamiya-Sekor C 55mm f/2.8 N · Mamiya-Sekor C 55mm f/2.8 S · Mamiya 645 55mm f/2.8 · Mamiya 645 55mm f2.8 N · Mamiya M645 55mm 2.8 · Sekor C 1:2.8 f=55mm · Mamiya A 55mm f/2.8 N/L · マミヤ セコールC 55mm F2.8 · マミヤ645 55mm F2.8 · セコールC 55mm F2.8 N

Variants & identification

Variant Mount Years Serial ranges Production
Mamiya-Sekor C 55mm f/2.8 (1975 original, 9 elements) · Reversed-telephoto type, 9 elements in 6 groups (Mamiya C brochure; Modern Photography, January 1976) Mamiya 645 1975 — —
Mamiya-Sekor C 55mm f/2.8 S (8 elements, 0.45 m) · Recomputed: 8 elements in 6 groups (Japanese Wikipedia; Hens; the N sheet carries the same count) Mamiya 645 — — —
Mamiya-Sekor C 55mm f/2.8 N · 8 elements in 6 groups (Mamiya N-era instruction sheet) Mamiya 645 1985 — —
Mamiya A 55mm f/2.8 N/L (leaf shutter) · Built-in leaf shutter with its own speed ring and PC socket, flash sync at every speed to 1/500 (Wikipedia; camera-wiki); cocked by hand, or automatically by the Power Drive Grip WG401 on the second-generation bodies Mamiya 645 — — —
  1. Element counts, closest focus, filter size, dimensions and weight for the C lens are from Mamiya's C-era lens brochure (cameramanuals.org); for the N and A N/L lenses from Mamiya's N-era 645 Interchangeable Lenses instruction sheet (Butkus library).
  2. The S lens's figures (8/6, 0.45 m, 58 mm) come from Japanese Wikipedia and Philip Hens's 2011 system list; its 335 g weight and the lack of a Mamiya document giving its dimensions mean those rest on one source.
  3. Aperture blade counts (6 on the plain lenses, 5 on the N/L) come only from the Wikipedia lens table; no Mamiya document consulted gives them.
  4. Variant start years are the body generations: C with the M645 (1975), N with the 645 Super (December 1985). The S lens is in the 1981 brochure and no source dates it; the A N/L and the end of C and S production are likewise undated.
How to tell them apart (expand)
  • Nine elements or eight: the original C lens is 9/6 with 0.55 m closest focus; the S, N and N/L are 8/6 with 0.45 m. A 45 cm figure on the distance scale rules out the original
  • S or N after the aperture on the name ring; the original has neither. Early S lenses carry a gold S sticker rather than an engraving (Wikipedia)
  • 58 mm filter on the C, S and N; 67 mm on the A N/L leaf-shutter lens, which also carries a shutter-speed ring
  • Needs its own hood: the Sekor C instruction sheet lists the 55mm among the lenses that take a special hood despite sharing the 58 mm thread with the 80mm and 110mm

Mamiya-Sekor C 55mm f/2.8 (1975 original, 9 elements):

  • Name ring reads Sekor C with nothing after the aperture; metal aperture ring; no S sticker or engraving
  • Mamiya's C-era brochure: 9 elements in 6 groups, 65° angle of view, f/22 minimum, 0.55 m closest focus, 58 mm filter, screw-in hood, 71 mm long, 70 mm diameter, 395 g
  • About twice the length of the 80mm f/2.8 and almost 14 oz, with the control rings in the same positions relative to the body (Modern Photography, January 1976)

Mamiya-Sekor C 55mm f/2.8 S (8 elements, 0.45 m):

  • S after the aperture: a gold S sticker on early examples, engraved on later ones (Wikipedia)
  • Eight elements in six groups, closest focus 0.45 m in place of 0.55 m, still 58 mm filter; 335 g against the original's 395 g (Hens; Wikipedia)

Mamiya-Sekor C 55mm f/2.8 N:

  • N after the aperture on the name ring; plastic aperture ring (Wikipedia)
  • Mamiya's N-era instruction sheet: 8 elements in 6 groups, 65°, f/22, 45 cm, 0.18× magnification, 58 mm filter, screw-in hood, 59.4 mm long, 70 mm diameter, 305 g

Mamiya A 55mm f/2.8 N/L (leaf shutter):

  • Engraved A rather than C before the focal length, and N/L after the aperture; a shutter-speed ring and a cable-release socket on the barrel (camera-wiki)
  • Mamiya's N-era instruction sheet: 8 elements in 6 groups, 65°, f/22, 45 cm, 67 mm filter (the only 55 with a 67 mm front), 61.5 mm long, 79.6 mm diameter, 520 g

Specifications

Formula
Retrofocus (reversed-telephoto) wide-angle: 9 elements in 6 groups on the original, recomputed to 8 elements in 6 groups for the S and N (Mamiya brochures; Modern Photography, January 1976)
Construction
9 elements / 6 groups
Aperture range
f/2.8–f/22
Diaphragm blades
6
Min. focus
0.55 m
Dimensions
70 × 71 mm
Weight
395 g
Filter
58 mm
Years manufactured
1975
Country
Japan
Coating
Multicoated: the C in Sekor C is Mamiya's multicoating mark; Modern Photography (1976) credited efficient multicoating for the low flare; the N lenses carry revised coatings (Wikipedia)
Original price
US$250 with hood and case (Modern Photography, January 1976); no Japanese price found (today $1,380)

What reviewers say

Optical Ratings

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

Chromatic aberration
lateral, at edges
Flare & ghosting
low
Distortion
slight barrel

History

The 55mm f/2.8 is the moderate wide-angle of the manual-focus Mamiya 645 system, a 34 mm equivalent that Modern Photography listed with the camera in September 1975 and tested in January 1976 at $250 with hood and case. The original is a reversed-telephoto design of 9 elements in 6 groups with a 65° angle of view, f/22 minimum, 0.55 m closest focus and a 58 mm filter thread shared with the 80mm f/2.8 and the 110, 150 and 210; at 71 mm long and 395 g it is about twice the length of the standard lens, though Modern Photography noted that its rings sit in the same places relative to the body, so handling barely changes.

Unlike the 45mm, whose three barrels carry one formula, the 55 was recomputed. The S version, in Mamiya’s 1981 US brochure and marked with a gold S sticker early and an engraving later, has 8 elements in 6 groups, focuses to 0.45 m and weighs 335 g by Philip Hens’s list; Wikipedia says the 45 and 55 were the only lenses given an S version and that both differ from their predecessors; for the 55 the element count confirms an optical change, where the 45 S kept its nine elements. The N of 1985 carries the eight-element optics into the ‘new’ cosmetic series with revised coatings and a plastic aperture ring, and Mamiya’s N-era instruction sheet puts it at 59.4 mm and 305 g, the lightest of the three. A fourth, the A 55mm f/2.8 N/L, wraps the same 8/6 glass around a leaf shutter with its own speed ring and PC socket for flash sync to 1/500 s, takes 67 mm filters and weighs 520 g. Neither the S nor the N/L is dated by any source consulted.

The two magazine tests, twenty-four years apart, describe different lenses. Modern Photography’s 1976 sample of the nine-element lens resolved 74 lines/mm at the centre wide open but showed strong orange fringing on the bench, spherical flare until f/5.6, significant lateral colour at the edges and some decentring; flare in pictures was low, which the magazine credited to the multicoating. Popular Photography’s 2000 sample of the N lens measured 0.75 percent barrel distortion, centre very good at f/2.8 to f/4 and excellent from f/5.6, corners excellent from f/4, fall-off gone by f/4 and a slight softening at f/2.8 in the field, with an optimum at f/8. Wyatt Ryan on 35mmc, shooting a C lens on a 1000S, says only that it is small, mostly metal and glass, hand-holdable at 1/60 s, and has barely left his camera.

When buying, the distance scale is the quickest sort: a lens that focuses to 0.45 m is an S, N or N/L, and a 0.55 m scale is the original nine-element lens. The S sticker can be missing on an early S, so count on the closest focus rather than the label. Check that the A/M lever moves the diaphragm and that the meter coupler on the aperture ring is intact; on the N/L, that the leaf shutter cocks and fires at every speed, since on first-generation bodies and without the WG401 grip it must be cocked by hand. The 645 AF 55mm f/2.8 and 55mm f/2.8 LS D are autofocus lenses for the 645AF bodies and are not covered here.

What remains open: the years of the S and N/L lenses and the end of C production; the S lens’s dimensions and the N/L shutter’s speed range from a Mamiya document; the blade counts, which only the Wikipedia table gives; and any Japanese list price. No licensed photograph of the lens or made with it was found on Wikimedia Commons.

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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

Sample photo wanted — shot with a Mamiya-Sekor C 55mm f/2.8 (645)? We'd love to feature it (with credit).

Live listings

Asking price, USD: a median of $340 across 45 fixed-price listings on 2026-09-19 (middle half $300–$380). First day tracked.

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

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Listings updated 2026-09-19. Links go to the shop or marketplace that carries the item.

Related: Mamiya-Sekor C 110mm f/2.8 (645) · Mamiya-Sekor C 150mm f/3.5 (645) · Mamiya-Sekor C 45mm f/2.8 (645) · Mamiya-Sekor C 80mm f/1.9 (645) · Mamiya-Sekor C 80mm f/2.8 (645)

Sources (13)

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.