Mamiya-Sekor Reflex C 500mm f/8 (645)

Mamiya · Mamiya 645 · 1975

single source, unconfirmed

Also known as: Mamiya-Sekor Reflex C 500mm f/8 · Mamiya Sekor Reflex C 500mm f8 · Mamiya 645 500mm f/8 Reflex · Mamiya 645 500mm f8 mirror · Mamiya Reflex 500/8 · Mamiya RX 500mm f8 · マミヤセコールレフレックスC 500mm F8 · マミヤ645 500mm F8 レフレックス · セコールレフレックスC 500mm F8

Variants & identification

Variant	Mount	Years	Serial ranges	Production
Mamiya-Sekor Reflex C 500mm f/8	Mamiya 645	1975	—	—

Construction (7 in 5) and closest focus (4 m) are agreed by Japanese Wikipedia and the English Wikipedia table; dimensions (135 × 101 mm), weight (880 g) and the built-in hood come only from the English table, so the page carries the single-source flag.
The filters: Japanese Wikipedia says five dedicated filters (専用5種), the English table says drop-in. Both describe rear filters; the number is carried on the Japanese source.
No source consulted dates the lens. The year is the C line's start with the M645 (June 1975, Japanese Wikipedia). It is in camera-wiki's original C list and in Mamiya's Sekor C sheet, and absent from the 645 Pro TL book of 1997.
The Sekor C 500mm f/5.6 (refracting, 105 mm filter) and the A 500mm f/4.5 APO are different lenses at the same focal length; the RZ67's Sekor Z 500mm f/8 is a refracting lens for another mount.

How to tell them apart (expand)

Mirror lens: a stubby barrel with a large front window and a central obstruction visible through it; there is no aperture ring, which separates it at a glance from the long refracting 500mm f/5.6
Name ring reads Reflex C; camera-wiki's 'RX' is its abbreviation, not an engraving confirmed here
Rear drop-in filters and a built-in hood; 645 bayonet with the A/M lever and meter coupler of the other C lenses

Mamiya-Sekor Reflex C 500mm f/8:

Short, fat mirror-lens barrel: 135 mm long and 101 mm across for a 500 mm focal length, 880 g, with a built-in hood (Wikipedia table)
No aperture ring: f/8 is fixed, and exposure is set by shutter speed or neutral-density filters
Filters drop into the rear of the lens; Japanese Wikipedia says five dedicated filters, the English table 'drop-in'
Closest focus 4 m (both wikis); camera-wiki lists it as 'RX 500mm f8 reflex' among the original C lenses

Mamiya-Sekor Reflex C 500mm f/8: The one version. Mamiya's Sekor C instruction sheet calls it a compactly designed telescope lens for sports or any distant subject. camera-wiki files it with the original C lenses, and no source consulted dates it, so the year is the C line's start in 1975. It is absent from the 645 Pro TL instruction book of 1997, which lists only the refracting 500mm f/5.6 and the A 500mm f/4.5 APO at this focal length, so it had gone by then.

Specifications

Formula: Catadioptric (mirror) telephoto, 7 elements in 5 groups, fixed f/8 (Japanese Wikipedia 5群7枚; Wikipedia table)
Construction: 7 elements / 5 groups
Aperture range: f/8–f/8
Min. focus: 4 m
Dimensions: 101 × 135 mm
Weight: 880 g
Filter: Rear drop-in filters, five dedicated ones (Japanese Wikipedia)
Years manufactured: 1975
Country: Japan
Coating: Multi-coated: Mamiya's Sekor C sheet says all the lenses for the M645 have been multi-coated, and the C in Sekor C is Mamiya's multicoating mark (Wikipedia)

What reviewers say

No reviews aggregated yet — this family is still in the research queue. Written one? We'd love to index it.

History

The Reflex C 500mm f/8 is the mirror telephoto of Mamiya’s manual-focus 645 system, the short way to a 310 mm equivalent on 35mm film. Japanese Wikipedia and the English Wikipedia table agree on a catadioptric construction of 7 elements in 5 groups and a closest focus of 4 m; the English table adds a barrel 135 mm long and 101 mm across, a built-in hood and 880 g, against the refracting Sekor C 500mm f/5.6’s long tube and 105 mm front filter. Mamiya’s own Sekor C instruction sheet gives it one sentence: a compactly designed telescope lens that fulfils its performance in photographing sports or any distant subject. Like every mirror lens it has no diaphragm, so f/8 is the only aperture, and the filters drop into the rear of the lens, a set of five dedicated ones by the Japanese list.

There is one version and no date. camera-wiki files it with the original C lenses as ‘RX 500mm f8 reflex’, Mamiya’s sheet of the 645 Super years still describes it, and the 645 Pro TL instruction book of 1997 does not list it at all, its 500s being the f/5.6 and the A 500mm f/4.5 APO. The year carried here is therefore the C line’s start with the M645 in June 1975, a floor rather than a launch date, and the end lies somewhere between the Super and the Pro TL. No N version is recorded by any source consulted.

No review of this lens was found by the searches made for this page, only dealer listings, so nothing can be said here about its rendering beyond what mirror optics imply: ring-shaped out-of-focus highlights, a fixed aperture and a weight and length that a refracting 500 of this speed could not match. With no diaphragm, exposure is set by shutter speed and by neutral-density filters in the rear holder alone, which decides the film for bright days.

When buying, look through the front for haze or fungus on the mirror coatings, which cannot be cleaned, check that the rear filter holder is present with at least a clear filter in it, since the optical path is computed with one, and work the long focus throw for stiffness. Make sure the seller’s ‘500mm f/8’ is this lens and not the RZ67’s Sekor Z 500mm f/8, a refracting lens for another mount. What remains open: a launch year and a discontinuation year, a list price in any currency, and any independent test.

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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 Reflex C 500mm f/8 (645)? We'd love to feature it (with credit).

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