Auto Rikenon 50mm f/2 (M42)
Ricoh · M42 · 1976 · Six elements in five groups
Also known as: Auto Rikenon 50mm f2 · Auto Rikenon 50mm f/2 · Auto Rikenon 1:2 f=50mm · Auto Rikenon 1:2 50mm · Ricoh Auto Rikenon 50mm f2 · Rikenon Auto 50mm f2 · Ricoh 50mm f2 Rikenon Auto · Ricoh 50mm f2 Auto Rikenon · Rikenon 50mm f2 M42 · Ricoh Rikenon 50mm f2 M42 · Ricoh 50mm f2 M42 · Rikenon 2/50 · Auto Rikenon 50mm 1:2 · Rikenon 50 mm f/2 · オートリケノン 50mm F2 · Rikenon 1:2 50mm M42 · Rikenon 1:2 f=50mm M42 · Rikenon 50mm 1:2 M42 · Rikenon 50 mm f/2 M42
Variants & identification
| Variant | Mount | Years | Serial ranges | Production |
|---|---|---|---|---|
| AUTO RIKENON 1:2 f=50mm | M42 | — | — | — |
- Six elements in five groups: Ricoh's Singlex II instruction book, Dr. Ricoh's Rikenon list and camera-wiki's Singlex II page agree. The 52 mm filter and the f/16 smallest stop are from Dr. Ricoh's list; f/16 is also the last stop on the aperture ring in Kamerastore's photographs.
- Closest focus, weight and size are left out of the specification rows because the two sources disagree. Dr. Ricoh's list gives 150 cm closest focus, 60 mm diameter, 52 mm length and 200 g; Kamerastore's listing gives 0.5 m, 48 × 62 mm and 230 g, plus six diaphragm blades. Dr. Ricoh gives the same 150 cm for the M42 50mm f/1.7 in the adjacent row, which may be an error in the table rather than a measurement; no maker document gives a closest-focus figure.
- The year is that of the earliest dated document found naming the lens: Ricoh dates the Singlex II, whose instruction book lists it, to August 1976. The SLX 500, which Ricoh dates to 1975, came with a 50 mm lens according to its instruction book, which does not give the aperture; a later Ricoh product catalogue, of the XR500 era, names the 50mm Auto Rikenon f/2.0 and f/2.8 as the SLX 500's standard lenses, so the lens may be a year older than this page says. The Singlex TLS instruction book lists a 50mm f/1.7 and 55mm lenses but no 50mm f/2, and camera-wiki gives the TLS 401's standard lenses as the 55mm f/1.4, 50mm f/1.7 and 55mm f/2.8. Japanese Wikipedia captions its photograph of the lens “1960年代？” with a question mark. No first or last year of manufacture is published.
- No launch price is on record. Ricoh's Japanese pages price the Singlex TLS and TLS 401 only with the 55mm f/1.4 and f/1.8, and the Singlex II, SLX 500 and Auto TLS EE were export bodies with no Japanese price.
- Maker unknown. On MFLenses (August 2022) the member D1N0 thought the M42 Rikenon 50s look like Cosina lenses made to Ricoh's specification; that is an opinion, not a record. The Tomioka and Nitto Optics attributions quoted in the same thread concern the K-mount versions (Tomioka for the 0.45 m XR Rikenon and the L, Nitto for the S, the P and the plain Rikenon), not this lens.
- No Sears-badged M42 50mm f/2 has been confirmed. Sears sold the Singlex TLS as the Sears TLS with Auto Sears lenses, but no example or catalogue entry for an Auto Sears 50mm f/2 in screw mount is on record, so none is listed.
- An MFLenses member (August 2022) described the M42 Rikenon 50mm f/2 he had just bought as having a rubber grip. Whether that is a different barrel from the pyramid-knurled one in the photographs here is not known, so no second variant is listed.
How to tell them apart
- Says AUTO RIKENON and 1:2 f=50mm on the front ring, with no XR and no P: XR Rikenon and Rikenon P 50mm f/2 lenses are Pentax K bayonet lenses for the 1977-on XR bodies, a different page
- A screw thread at the back, not a three-lug bayonet: every K-mount Rikenon has the bayonet
- No EE setting on the aperture ring: this is an ordinary automatic-diaphragm lens, not one of the Auto Rikenon EE lenses made for the Auto TLS EE
AUTO RIKENON 1:2 f=50mm:
- Front ring engraved AUTO RIKENON 1:2 f=50mm in white on black, with a thin bright ring at the edge of the front barrel. The country line differs between photographed copies: LENS MADE IN JAPAN on Simon Hawketts's, LENS JAPAN on Kamerastore's
- Black barrel with a pyramid-knurled focusing grip; distance scale in metres (green) and feet (white); aperture ring 2 – 2.8 – 4 – 5.6 – 8 – 11 – 16
- Rear: 42 mm screw thread with the stop-down pin of an automatic-diaphragm M42 lens
- AUTO RIKENON 1:2 f=50mm: The only version this entry can show from photographs: Simon Hawketts's Singlex II on Everything Vintage wears one, and Kamerastore's M42 listing shows the same knurled grip, scales and AUTO R… lettering, though its front ring reads LENS JAPAN where Hawketts's reads LENS MADE IN JAPAN. Ricoh's Singlex II instruction book lists the lens among the standard lenses for that body, as "50 mm Auto Rikenon f/2.0, 5 groups 6 elements".
Specifications
- Formula
- Six elements in five groups
- Construction
- 6 elements / 5 groups
- Aperture range
- f/2–f/16
- Filter
- 52 mm
- Country
- Japan
What reviewers say
No reviews aggregated yet — this family is still in the research queue. Written one? We'd love to index it.
Optical formula — Six elements in five groups
No cross-section found: Ricoh's Singlex II instruction book and Dr. Ricoh's list give the 5-group / 6-element count without a drawing, and no patent has been tied to this lens.
History
The Auto Rikenon 50mm f/2 is one of Ricoh’s screw-mount standard lenses: a six-element, five-group f/2 with automatic diaphragm, a 52 mm filter thread and a smallest stop of f/16. Ricoh’s instruction book for the Singlex II of August 1976 names it among that body’s four standard lenses, alongside the 55mm f/1.4, the 50mm f/1.7 and the 50mm f/2.8, and that is the earliest dated document found that mentions it. The Singlex TLS book lists a 50mm f/1.7 and 55mm lenses but no f/2. That fits a lens of the late screw-mount years, when Ricoh was making the Singlex II, SLX 500 and Auto TLS EE as low-cost bodies for export only (Ricoh names the American market for the Singlex II). Japanese Wikipedia’s “1960s?” caption carries its own question mark. No launch price and no production dates have been published.
It fits every M42 body, and every Ricoh screw-mount reflex, by the same thread. On the Singlex TLS, TLS 401, SLX 500 and Singlex II it is an ordinary automatic-diaphragm lens: the meter reads it stopped down, with the camera’s preview or meter switch closing the aperture. That is what Ricoh’s pages say for the TLS and TLS 401 and what the SLX 500 and Singlex II instruction books describe; Ricoh’s own pages for the SLX 500 and Singlex II say open-aperture metering, which their books do not bear out. It is not an EE lens. On the Auto TLS EE, shutter-priority automation needs the Auto Rikenon EE lenses. Ricoh’s Auto TLS EE instruction book has a non-EE lens used either at full aperture, with the lens selection dial set to its maximum aperture and the f-number the needle shows set on the ring by hand, or stopped down with the previewer switch.
Only one version has been confirmed: black barrel, a pyramid-knurled grip, and AUTO RIKENON 1:2 f=50mm on the front ring, with LENS MADE IN JAPAN on one photographed copy and LENS JAPAN on another. Who made it is not on record. One MFLenses member thinks the M42 Rikenon 50s look like Cosina lenses; the Tomioka and Nitto Optics attributions that are sometimes repeated for “the Rikenon 50mm f/2” belong to the later K-mount XR Rikenon versions. The two published sets of figures disagree on closest focus, size and weight (Dr. Ricoh’s list against a Kamerastore listing), so those are given in the notes rather than as specifications.
When buying, check the back first. Most Rikenon 50mm f/2 lenses on the market are XR Rikenon, plain Rikenon or Rikenon P lenses in the Pentax K bayonet, and a title that says only “Ricoh 50mm f2 Rikenon” may be either. The M42 lens has a screw thread and no XR or P on the ring. As with any automatic M42 lens, the aperture should snap shut cleanly when the rear pin is pressed and open again when it is released. Ricoh’s Singlex II book says its standard lenses have an Auto/Manual switch; on M the lens should close to the stop set on the ring and stay there. Kamerastore’s out-of-stock page (November 2026) gives an “average Certified condition price” of €65 on its European storefront and ¥12,200 on its Japanese one. That is a dealer’s reference retail figure, not a sale or auction result.
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
More sample photos elsewhere
- Simon Hawketts: Ricoh Singlex II with the Auto Rikenon 50mm f/2, front ring legible (Everything Vintage)
- Kamerastore: Ricoh 50mm f2 Rikenon Auto (M42), dealer photographs
These photographers keep all rights to their work — enjoy it at the source.
Sample photo wanted — shot with a Auto Rikenon 50mm f/2 (M42)? We'd love to feature it (with credit).
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