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

Mamiya-Sekor C 500mm f/5.6 (645)

Mamiya · Mamiya 645 · 1979

Also known as: Mamiya-Sekor C 500mm f/5.6 · Mamiya Sekor C 500mm f5.6 · Mamiya 645 500mm f/5.6 · Sekor C 500/5.6 · マミヤ セコールC 500mm F5.6 · マミヤ 645 500mm F5.6

Variants & identification

Variant Mount Years Serial ranges Production
Mamiya-Sekor C 500mm f/5.6 Mamiya 645 1979 — —
  1. Optical construction, angle of view, minimum aperture, closest focus, magnification, filter size, hood, dimensions and weight are from Mamiya's own tables: the M645 1000S manual and the Sekor C instruction sheet (both at butkus.org) and the 645 Pro-era Interchangeable Lenses product sheet, which all print the same figures.
  2. The year is a floor, not a launch date. The lens is on Mamiya's M645J-era system chart, which shows the M645J of 1979 alongside the M645 and 1000S, and camera-wiki lists it among the original C lenses, but no source consulted dates its introduction. 1979 is the earliest Mamiya document found that shows it; the true first year may be earlier.
  3. The 9 aperture blades are Wikipedia's figure, matched by Kamerastore's listing; Mamiya's tables give no blade count. Dealer listings quoting 3,000 g and a 95 mm filter are wrong by Mamiya's own table (2,280 g, 105 mm).
  4. The 500mm f/4.5 APO of the 645 Pro years and the Reflex 500mm f/8 (7 elements in 5 groups, fixed f/8, 880 g) are different lenses.
How to tell them apart (expand)
  • 105 mm filter thread, the largest in the 645 system; Mamiya sold filters in that size for this lens alone
  • Tripod foot on the barrel; the only manual-focus 645 lens below the 300mm f/2.8 APO to have one
  • 358 mm long and 2,280 g by Mamiya's table; f/45 minimum aperture where every other 645 lens stops at f/22 or f/32
  • Mamiya's M645 manual recommends the all-matte No.2 focusing screen for 'slow lenses such as the 500mm f/5.6' because the split-image and microprism aids darken

Mamiya-Sekor C 500mm f/5.6:

  • Mamiya's tables: 6 elements in 5 groups, 8° angle of view, f/5.6–45, 9 m closest focus, 0.07×, 105 mm filter, built-on hood, 358 × 114 mm, 2,280 g
  • Tripod foot on the barrel and a very long built-in hood, both visible in Mamiya's product photographs
  • Never given an N or ULD marking in any Mamiya document consulted: the 645 Pro manual of 1992 lists it as plain '500mm f/5.6' beside the 'ULD300mm f/5.6N'

Specifications

Construction
6 elements / 5 groups
Aperture range
f/5.6–f/45
Diaphragm blades
9
Min. focus
9 m
Dimensions
114 × 358 mm
Weight
2280 g
Filter
105 mm
Years manufactured
1979
Country
Japan
Coating
Multi-coated: Mamiya's manual says 'all the lenses for your camera have been multi-coated', and the C in Sekor C denotes multicoating (Wikipedia)

What reviewers say

Optical Ratings

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

Chromatic aberration
visible, stop down
Optical formula

History

The 500mm f/5.6 is the longest refracting lens Mamiya made for the manual-focus 645, a 310mm equivalent on 35mm film by Mamiya’s table. Mamiya’s own figures: 6 elements in 5 groups, an 8° angle of view, f/5.6 to f/45, closest focus at 9 m for 0.07×, a 105 mm filter thread, a built-in hood, a tripod foot, and 2,280 g in a barrel 114 mm across and 358 mm long. The cross-section in the M645 1000S manual shows a cemented pair and a singlet at the front and two small elements far back near the mount, the layout of a classic long telephoto, and nothing about it is compact: the front element is bigger than most 645 bodies are tall.

Mamiya’s documents show one version and never give it a suffix. It is on the M645J-era system chart, in the 1000S manual, in the Sekor C sheet of the M645 Super years and in the 645 Pro manual of 1992, always as plain 500mm f/5.6, while the neighbouring 300mm gained ULD and N markings. Camera-wiki lists a 500mm f/5.6N and a Japanese dealer describes a ‘New’ type with an all-black barrel and no silver front ring, so the barrel trim evidently changed at some point, but no Mamiya document consulted records a new version and the optics did not change. When it was introduced is not recorded anywhere consulted either; the 1979 M645J chart is the earliest Mamiya document found that shows it, and the page uses that as a floor.

There is almost no published reviewing. Lensvana gives it an honourable mention as ‘very sharp, bulky, and more of a collector or specialty lens than a daily shooter’. The useful testimony is in two forum threads. On Flickr’s Mamiya 645 Lenses group an owner who tried it on a digital back found it sharp, sharpest at f/8, with both longitudinal and lateral colour fringing that stopping down controls, and summarised the handling as ‘big and heavy’. A Luminous Landscape thread on using it for birds agrees: soft at f/5.6, ‘gets sharp immediately at 8.0’, chromatic aberration the real limit on small-pixel sensors, and 2.2 kg that rules out handholding. Prices in those threads ran from $345 to $550.

Buying one is mostly a question of whether you can carry it. Check the tripod foot for stripped threads, the long built-in hood for dents, and the focus helicoid, which moves a lot of glass and stiffens with old grease; the 105 mm front element is expensive to replace if scratched. Mamiya’s own advice from the M645 manual still applies: use the all-matte No.2 screen, because the split-image and microprism spots go dark at f/5.6 on a lens this long. Extension tubes bring the 9 m close focus in, and Mamiya’s 2× tele-converter takes it to 1000mm at f/11. Do not confuse it with the Reflex 500mm f/8, a fixed-aperture mirror lens at 880 g, or with the later 500mm f/4.5 APO.

What remains open: the launch year, a list price in any currency, whether the all-black barrel corresponds to a dated change, and a discontinuation date.

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 C 500mm f/5.6 (645)? We'd love to feature it (with credit).

Live listings

Asking price, USD: a median of $400 across 13 fixed-price listings on 2026-09-21 (middle half $380–$440). First day tracked.

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

Show 9 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 2026-09-21. Links go to the shop or marketplace that carries the item.

Related: Mamiya-Sekor C 300mm f/5.6 (645) · Mamiya APO A 300mm f/2.8 (645) · Mamiya-Sekor C 210mm f/4 (645) · Mamiya-Sekor Zoom C 105-210mm f/4.5 (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.