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

Mamiya-Sekor 65mm f/4.5 (RB67)

Mamiya · Mamiya RB67 · 1970

single source, unconfirmed

Also known as: Mamiya RB67 65mm f/4.5 · Mamiya RB67 65mm f4.5 · Mamiya-Sekor 65mm f/4.5 · Mamiya-Sekor C 65mm f/4.5 · Mamiya Sekor C 65mm f4.5 RB67 · Sekor C 65/4.5 · マミヤ RB67 65mm · セコールC 65mm F4.5

Variants & identification

Variant Mount Years Serial ranges Production
Mamiya-Sekor 65mm f/4.5 (1970, single-coated, 8/8, no floating ring) · Seiko #1, T and 1s–1/400, M-X sync Mamiya RB67 1970–1974 — —
Mamiya-Sekor C 65mm f/4.5 (1974, multicoated, 8/7, floating ring) · 8 elements in 7 groups with a built-in floating system (Interchangeable Lenses for Mamiya RB67 booklet; Pro-S manual) · Seiko #1, T and 1s–1/400, M-X sync Mamiya RB67 1974–1990 — —
  1. Element and group counts, picture angles, minimum apertures, hoods and weights are from Mamiya's own lens booklets and the RB67 Professional and Pro-S manuals as hosted by butkus.org. Closest-focus figures (from the front rim) are from Japanese Wikipedia, which cites Mamiya catalogue R790503.
  2. The RB67 Pro-SD's 65 is the Mamiya K/L 65mm f/4 L of 1990: 9 elements in 8 groups with ultra-low-dispersion glass and an adjustable floating element, 68°, closest focus 348 mm, 106 × 97.2 mm, 1,070 g (Mamiya Pro SD lens page; Japanese Wikipedia; camera-wiki). It is a different maximum aperture and so, by the site's one-aperture rule, a different family; it is not on this page.
  3. The Sekor NB (new barrel) 65, 90 and 127 are listed only by Japanese Wikipedia, which says the barrel was redesigned and gives no date. Carried as a single-source claim.
  4. Generation start years are those of the bodies the lenses launched with (Professional 1970, Pro-S 1974). No source gives a month for the 65's own changeover, and no discontinuation dates are published.
How to tell them apart (expand)
  • Two name rings for the f/4.5: Mamiya-Sekor (1970, single-coated, chrome ring early) and Mamiya-Sekor C (1974, multicoated). A ring reading K/L 65mm f/4 L is the Pro-SD lens and a different family
  • The floating ring is the quickest sort: the Sekor C has one on the front of the barrel with its own distance scale, the 1970 Sekor does not
  • Slip-on 80 mm square hood shared with the 50, not the screw-in round hood of the longer lenses; 77 mm filter thread on both versions
  • Weight barely separates them: 840 g for the Sekor, 835 g for the Sekor C
  • On the Pro-SD's 61 mm mount both versions want the 7 mm adapter ring Mamiya recommends for light sealing; on the Pro and Pro-S they mount directly
  • Every version carries a Seiko #1 leaf shutter cocked by the body's lever, with cocking pins on the barrel that must be turned fully to the red mark before mounting

Mamiya-Sekor 65mm f/4.5 (1970, single-coated, 8/8, no floating ring):

  • Engraved Mamiya-Sekor 1:4.5 f=65mm with no C after the name; chrome front ring on the early barrels
  • No floating ring: the 1970 Lenses for Mamiya RB booklet gives floating-system instructions for the 50 alone, and its 65 is a plain barrel with the depth-of-field scale on the front
  • Single anti-reflection coating (camera-wiki); the booklet gives 8 elements in 8 groups, picture angle 68°10', minimum aperture 32, slip-on 80 mm square hood, 29 5/8 oz (840 g)
  • A second barrel design, the Sekor NB (new barrel), was sold for the 65, 90 and 127 before the C series; Japanese Wikipedia lists it, and no other source consulted describes it³

Mamiya-Sekor C 65mm f/4.5 (1974, multicoated, 8/7, floating ring):

  • C engraved after Sekor on the name ring; black barrel
  • A floating ring with its own distance scale on the front of the barrel, like the 50's: the C booklet's page 7 covers 'the 50mm and 65mm Lenses' together, and the Pro-S manual says the 65 'has a built-in floating system which moves a portion of the lens system to the front or rear'
  • Interchangeable Lenses for Mamiya RB67 booklet: 8 elements in 7 groups, picture angle 69°, minimum aperture 32, slip-on 80 mm hood, 29.4 oz (835 g); the Pro-S manual gives 29-7/16 oz (835 g)
  • Japanese Wikipedia: closest focus 0.085 m from the front rim

Specifications

Formula
8 elements in 8 groups (Sekor); 8 elements in 7 groups with floating system (Sekor C)
Construction
8 elements / 8 groups
Aperture range
f/4.5–f/32
Shutter
Seiko #1 leaf shutter in the lens on both versions: T and 1s–1/400, cocked by the body's lever, M-X flash sync at every speed. No B setting; long exposures use T, closed by turning the speed ring toward 1 second
Weight
840 g
Filter
77 mm
Years manufactured
1970
Country
Japan
Coating
Single-coated on the Mamiya-Sekor; multicoated on the Sekor C of 1974

What reviewers say

Optical formula — 8 elements in 8 groups (Sekor); 8 elements in 7 groups with floating system (Sekor C)

History

The 65mm f/4.5 is the Mamiya RB67’s moderate wide-angle, 68 degrees across the 6 × 7 frame, the focal length Mamiya’s later literature calls “the most popular wide angle focal length in 6x7cm format” and the equivalent of 32 mm on 35 mm film. It was in the seven-lens line that launched with the RB67 Professional in 1970. Mamiya’s Lenses for Mamiya RB booklet gives the first version as 8 elements in 8 groups, no cemented surfaces, a picture angle of 68°10’, minimum aperture f/32, the slip-on 80 mm square hood it shares with the 50, 77 mm filters and 840 g. Japanese Wikipedia, citing Mamiya’s catalogue, puts closest focus at 0.08 m from the front rim on the body’s own bellows. The Seiko #1 shutter offers T and 1 to 1/400 second with M-X sync at every speed and is cocked by the lever on the body.

The 1974 Sekor C is where this lens differs from its neighbours: the multicoating came with a floating system that the 1970 lens did not have. Mamiya’s 1970 booklet gives floating-ring instructions for the 50 alone; the 1974 Interchangeable Lenses for Mamiya RB67 booklet heads the same page “Instructions for the 50mm and 65mm Lenses”, and the Pro-S manual says the 65 “has a built-in floating system which moves a portion of the lens system to the front or rear, according to the photographing distance, in order to obtain sharp resolution down to the picture circumference”. The formula became 8 elements in 7 groups, the picture angle is printed as 69°, the weight fell 5 g to 835 g, and the closest focus moved from 0.08 to 0.085 m from the rim. The routine is the 50’s: focus with the body’s knob, read the distance, set the front ring to match, and use f/16 or smaller inside 1 m. Between the two, Japanese Wikipedia alone records a Sekor NB (new barrel) 65, carried here as an alias and a single-source note.

The floating ring is therefore the quickest way to tell the versions apart, quicker than the name ring, since the weights are within 5 g of each other. No ring and no C is the 1970 lens; a ring with its own distance scale on the front, and C after Sekor, is 1974 on. A ring reading K/L 65mm f/4 L is the Pro-SD’s 65 of 1990, a 9-element lens with ultra-low-dispersion glass and an adjustable floating element that Mamiya’s own page gives as 348 mm closest focus and 1,070 g; it is a different maximum aperture and so a different page, though it fits the older bodies once its 7 mm rear ring is removed. Going the other way, either f/4.5 lens on a Pro-SD wants the 7 mm ring Mamiya recommends for light sealing on the 61 mm mount.

Of the RB67’s four short lenses this is the one the reviewers indexed here have written least about. No article on Emulsive, 35mmc, Kosmo Foto, analog.cafe, Shoot It With Film, Japan Camera Hunter or the KEH blog was found that names the 65 and says anything about it; the only verdict that reaches it is Japan Camera Hunter’s system piece, which reports the argument over whether the C lenses trail the K/L and finds nothing wrong with his own C glass. The Pro-SD-era Mamiya page’s praise for the 65 mm focal length, natural perspective with the least edge distortion of the wide range, is written for the f/4 successor. Casual Photophile, Ken Rockwell and Lomography are not consulted by this catalogue.

The checks are the ones for any RB lens plus the ring. The Seiko #1 is cocked by the body and can drag at slow speeds or hang at T after years unused; the cocking pins must be turned fully to the red dot before mounting, and both booklets say a lens stored for a long time should have its shutter released. The 1970 lens has no cemented surfaces to separate, so look instead for haze and cleaning marks on its single coating; the Sekor C has one cemented pair, and it is worth a look for separation. On a Sekor C, turn the floating ring through its whole scale and confirm it moves freely, because a ring stuck at infinity leaves the corners soft at every close distance the C version was recomputed for. No launch price in yen or dollars for either version was found, no serial-number table exists, and the Sekor NB barrel’s date is unknown.

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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 65mm f/4.5 (RB67)? We'd love to feature it (with credit).

Live listings

Asking price, USD: a median of $240 across 43 fixed-price listings on 2026-09-19 (middle half $200–$260). 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 127mm f/3.8 (RB67) · Mamiya-Sekor 180mm f/4.5 (RB67) · Mamiya-Sekor 250mm f/4.5 (RB67) · Mamiya-Sekor 50mm f/4.5 (RB67) · Mamiya-Sekor 90mm f/3.8 (RB67)

Sources (8)

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.