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

Mamiya-Sekor 250mm f/4.5 (RB67)

Mamiya · Mamiya RB67 · 1970

single source, unconfirmed

Also known as: Mamiya 250mm f/4.5 RB67 · Mamiya RB67 250mm f4.5 · Mamiya-Sekor 250mm f/4.5 · Mamiya-Sekor C 250mm f/4.5 · Mamiya Sekor C 250mm f4.5 · Mamiya K/L 250mm f/4.5 L · KL 250mm f/4.5 L · KL 250mm f/4.5 APO L · Mamiya 250 4.5 RB · セコール 250mm F4.5 · セコールC 250mm F4.5 · マミヤ RB67 250mm · マミヤ KL 250mm F4.5

Variants & identification

Variant Mount Years Serial ranges Production
Mamiya-Sekor 250mm f/4.5 (1970 original, single-coated) · Seiko #1 mechanical leaf shutter, 1s–1/400 and T Mamiya RB67 1970–1974 — —
Mamiya-Sekor C 250mm f/4.5 (1974, multicoated) · Seiko #1 mechanical leaf shutter, 1s–1/400 and T Mamiya RB67 1974–1990 — —
Mamiya K/L 250mm f/4.5 L (1990, Pro-SD generation, non-APO) · Seiko #1 mechanical leaf shutter, 1s–1/400, T and B Mamiya RB67 1990 — —
Mamiya APO-K/L 250mm f/4.5 L (apochromat, Pro-SD generation) · 7 elements in 5 groups; two elements of ultra-low dispersion glass and one of anomalous dispersion glass (Mamiya APO lens booklet) · Seiko #1 mechanical leaf shutter, 1s–1/400, T and B Mamiya RB67 1990 — —
  1. Original and Sekor C figures are from the RB67 Professional and RB67 Pro-S instruction books at butkus.org; APO figures are from Mamiya's APO lens booklet at butkus.org; the non-APO K/L figures are from the RB67 Camera Guide (rb67.helluin.org), which quotes the lens's own manual for the element count, and are otherwise single-source.
  2. camera-wiki gives 7 elements in 5 groups for the non-APO K/L and 7 in 6 for the APO; the lens manual quoted by the RB67 Camera Guide and Japanese Wikipedia give 5 in 4 for the K/L, and Mamiya's booklet gives 7 in 5 for the APO. The maker's and the manual's figures are used.
  3. Generation years are the body years (Pro-S 1974, Pro-SD September 1990); no Mamiya document consulted gives a changeover date for the 250 itself, and no source dates the APO version separately from the other Pro-SD lenses.
How to tell them apart (expand)
  • The name ring sorts them: MAMIYA-SEKOR with a chrome front ring is the 1970 lens, SEKOR C the 1974 multicoated lens, K/L with no Sekor name the 1990 lens, and APO with a blue line around the front the apochromat
  • Weight separates the two Sekors: 1,310 g for the original against 1,020 g for the C, by the two instruction books
  • A K/L or APO lens has a removable 7 mm adapter ring at the rear; the Sekor versions need a separate mounting ring on a Pro-SD or an RZ67
  • Every version takes 77 mm screw-in filters and focuses on the body's bellows

Mamiya-Sekor 250mm f/4.5 (1970 original, single-coated):

  • Engraved MAMIYA-SEKOR 1:4.5 f=250mm, no C; chrome front ring; single coating (camera-wiki)
  • RB67 Professional instruction book: 5 elements in 4 groups, picture angle 20°, minimum aperture f/45, 77 mm filter, screw-in hood, 46-3/16 oz (1,310 g)
  • Closest focus 1.6 m from the front rim (Japanese Wikipedia)

Mamiya-Sekor C 250mm f/4.5 (1974, multicoated):

  • C after Sekor; black barrel; multicoated (camera-wiki)
  • Pro-S instruction book: 5 elements in 4 groups, picture angle 20°, minimum aperture f/45, 77 mm filter, screw-in hood, 36 oz (1,020 g)
  • Closest focus 1.57 m from the front rim (Japanese Wikipedia)
  • Two-letter date-code sticker on the rear of the lens (Mamiya Repair)

Mamiya K/L 250mm f/4.5 L (1990, Pro-SD generation, non-APO):

  • K/L on the barrel, no Sekor name, no blue line around the front (RB67 Camera Guide: 'the APO/L lenses has a blue line around the front of the lens, the non-APO lens does not')
  • 5 elements in 4 groups per the lens's own manual as quoted on the RB67 Camera Guide; Japanese Wikipedia adds that it includes ultra-low dispersion glass (超低分散レンズを含む)
  • 1,130 g, closest focus 1,860 mm, minimum aperture f/45, 20° (RB67 Camera Guide); Japanese Wikipedia gives 1.854 m, or 1.578 m from the front rim
  • Removable 7 mm adapter ring at the rear for Pro and Pro-S bodies (Pro-SD manual)

Mamiya APO-K/L 250mm f/4.5 L (apochromat, Pro-SD generation):

  • APO on the barrel and a blue line around the front of the lens (RB67 Camera Guide)
  • Mamiya's APO booklet: 7 elements in 5 groups, automatic diaphragm, minimum aperture f/45, closest focus 1,564 mm from the front rim, area covered 298 × 370 mm, 77 mm filter, screw-in hood attached, 137.8 mm long × 97.2 mm diameter, 1,370 g; angle of view 20°30' diagonal
  • Pincushion distortion 'less than 1%' per the booklet; no focus shift between visible and infrared

Serial-range notes

two-letter sticker on the rear of the lens
Mamiya dated RB and RZ lenses with a two-letter code stuck to the back of the lens: the first letter is the year, the second the month, A = January. Year letters run A–J for 1971–1980, A–T for 1981–2000 and A–N for 2001–2014, so the decade has to be read from the generation (Mamiya Repair). No serial-to-year table for the 250 has been published.

Specifications

Formula
5 elements in 4 groups (Mamiya-Sekor, Sekor C and K/L); 7 elements in 5 groups with two ULD elements on the K/L APO
Construction
5 elements / 4 groups
Aperture range
f/4.5–f/45
Shutter
Seiko #1 mechanical leaf shutter in every version, 1s–1/400 and T, flash sync at all speeds; the K/L and APO add a B setting (Pro-SD manual). Focusing is by the body's bellows, so the lens has no helicoid.
Weight
1310 g
Filter
77 mm
Years manufactured
1970
Country
Japan
Coating
Single coating on the 1970 Mamiya-Sekor; multicoated from the Sekor C of 1974; improved coatings again on the K/L and APO of 1990 (camera-wiki)

What reviewers say

Optical formula — 5 elements in 4 groups (Mamiya-Sekor, Sekor C and K/L); 7 elements in 5 groups with two ULD elements on the K/L APO

No cross-section found: the RB67 Professional, Pro-S and Pro-SD instruction books and Mamiya's APO lens booklet at butkus.org give specification blocks, entrance-pupil positions and depth-of-field tables without optical diagrams, and no Mamiya data sheet for the 250 is online.

History

The 250mm f/4.5 was the long end of the RB67 system at launch. The 1970 instruction book describes the lenses as running “from the 65 mm wide angle to the 250 mm telephoto” and gives the 250 its own specification block: 5 elements in 4 groups, a picture angle of 20°, f/4.5 to f/45, a 77 mm filter thread, a screw-in hood and 46-3/16 oz, or 1,310 g. Like every RB lens it has a Seiko #1 leaf shutter, 1 second to 1/400 with sync at every speed, and no focusing helicoid; the body’s bellows do that, which is why closest distances are quoted from the front rim and why the same lens focuses differently on the longer bellows of the Pro-SD. On the RB67 Flickr group the 250 is described as “almost exactly twice as long as the 127” and as a bit heavier and larger than the 180.

Four versions exist under this name and three of them share the five-in-four design. The single-coated Mamiya-Sekor of 1970 has a chrome front ring; the Sekor C, introduced with the Pro-S in 1974, is multicoated and, by the Pro-S instruction book, 1,020 g, nearly 300 g lighter than the original with the same element count and the same 20° and f/45. The Pro-SD of September 1990 brought the K/L 250mm f/4.5 L, listed in the Pro-SD manual simply as KL 250mm f/4.5: the RB67 Camera Guide calls it a newer optical formula, quotes its manual for 5 elements in 4 groups and gives 1,130 g and 1,860 mm, and Japanese Wikipedia says it includes ultra-low dispersion glass. camera-wiki’s seven-in-five count for this lens is the APO’s count and is not used here.

The fourth is a different lens. Mamiya’s booklet for the “RB Pro-SD apochromatic lenses” gives the APO-K/L 250mm f/4.5 L as 7 elements in 5 groups, combining “two lenses which use ultra low dispersion glass with one that uses anomalous dispersion glass”, with pincushion distortion under 1%, closest focus 1,564 mm from the front rim, 137.8 mm long by 97.2 mm across and 1,370 g. The booklet’s claim is that focus does not shift between visible light and infrared and that field curvature at short distances has been remedied. The RB67 Camera Guide gives the field mark: a blue line around the front of the lens on the APO, none on the plain K/L. The RZ67’s own APO 250mm f/4.5 has the same 7/5 construction, 1.86 m closest focus and 1,340 g in the Pro IID brochure.

Mounting is where the generations bite. The Pro-SD enlarged the throat from 54 to 61 mm, so K/L and APO lenses carry a 7 mm adapter ring at the rear that comes off for a Pro-SD and stays on for a Pro or Pro-S; the APO booklet says the 210, 250 and 350 APO lenses work on a Pro-S that way, while the APO 500 will not fit one. The Sekor and Sekor C go on a Pro-SD or an RZ67 with a separate mounting ring, which Reznitsky’s chart and the RZ67 Pro IID manual both recommend, and the pre-1978 lenses are listed as unusable on an RZ, whose manual asks that older RB lenses have their shutter torque checked by a Mamiya service department first.

Reviews of the 250 specifically are thin. Lubomir Drapal at 35mmc added a Sekor 250 for foggy autumn mornings and got what he imagined; Scott McClarin at Emulsive calls the Sekor C lenses exceptionally sharp and warns that older lenses show more chromatic aberration; Mark Foster at Japan Camera Hunter trusts all RB lenses to be sharp and sees the C-versus-K/L question as a division among owners rather than a difference he has found. What to check is the same as for any RB lens: every shutter speed, the slow speeds especially, the cocking action on and off the body, and the diaphragm blades. Open questions: the first year of the K/L and the APO beyond the Pro-SD’s 1990, the meaning of the L-A suffix Japanese sources attach to the plain K/L, and any list price in yen or dollars, none having been found.

Expand Collapse

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 250mm f/4.5 (RB67)? We'd love to feature it (with credit).

Live listings

Asking price, USD: a median of $140 across 28 fixed-price listings on 2026-09-19 (middle half $100–$150). First day tracked.

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

Show 73 more listings

Buying from Yahoo! Auctions outside Japan. It is a domestic marketplace: sellers ship within Japan, and most will not register an overseas buyer. A proxy service bids on your behalf, receives the item and forwards it, for a fee and a wait. Buyee, Jauce and ZenMarket each accept a Yahoo auction number directly. Listed alphabetically for information — none is recommended over another, and none of these is an affiliate link.

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 50mm f/4.5 (RB67) · Mamiya-Sekor 65mm f/4.5 (RB67) · Mamiya-Sekor 90mm f/3.8 (RB67)

Sources (15)

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.