Komura 300mm f/5 (Bronica, Unihelicoid)
Sankyo Koki · Bronica S · 1965 · Long-focus lens head, 4 elements in 3 groups
Also known as: Komura 300mm f/5 Bronica · Komura 300mm F5 for Zenza Bronica · Sankyo Koki Komura 300mm f5 Bronica · Sankyo Kohki Komura 300mm F5 Bronica S2 · Komura 300/5 Bronica Unihelicoid · Komura Unihelicoid II 300mm f5 · Komura 300mm f/5 for Bronica S2 S2A EC · Zenza Bronica Komura 300mm f5 · コムラー 300mm F5 ブロニカ · コムラー 300mm F5 ユニヘリコイド · 三協光機 コムラー 300mm F5 ゼンザブロニカ用
Variants & identification
| Variant | Mount | Years | Serial ranges | Production |
|---|---|---|---|---|
| Komura 300mm f/5 head on Unihelicoid II (new large bayonet, Bronica C and later) | Bronica S, large bayonet of the C/C2/S2/S2A/EC (Unihelicoid II) | 1965 | — | — |
| Komura 300mm f/5 head on Unihelicoid III (old large bayonet, Bronica Z/D and S) | Bronica S, old large bayonet of the Z/D and S (Unihelicoid III) | 1965 | — | — |
- Construction (3 groups, 4 elements), preset diaphragm, the 67 mm screw-in attachment and the Unihelicoid II/III versions are from Japanese Wikipedia's Komura list on the ゼンザブロニカ page, which gives no years, prices, weights or close-focus figures for any Komura lens. camera-wiki's Bronica lens list gives '300mm f5 Komura (focus mod II)' and does not define the term; 'focus mod II' against 'focus mod I' for the 200 mm matches the Unihelicoid II of the tele heads, but the page does not say so.
- Date: no source dates the Bronica Komuras. The year is approximate: a Unihelicoid II exists for the large bayonet that arrived with the Bronica C in December 1964, and Mike Eckman reproduces a 1965 EPOI dealer catalogue listing some forty Komura lenses from 28 mm to 800 mm, so the heads belong to the mid-1960s; which came first, the II or the III, and when either was dropped, is not recorded.
- Relatives: Japanese Wikipedia says the 300, 400 and 500 mm heads could also go on the Rollei SL66 with a Komura SL66 adapter, and that the lenses were later offered as head + helicoid + mount under the name コムラノンシステム67・35 for the Asahi Pentax 6×7, the Rollei SL66 and various 35 mm SLRs. Whether the Komuranon 300 mm head of that system is optically the same 4-element, 3-group lens is not stated. Sankyo Koki also sold a 300mm f/5 Komura for 35 mm cameras on its 39 mm Unidapter mount; its relation to the Bronica head is not documented.
- The コムラー テレモア66 X2 For BRONICA 2× converter fits between the body bayonet and the focusing unit and works on the S2 and EC series, but Japanese Wikipedia says it cannot be used with lenses that mount directly on the body bayonet, which is how the Unihelicoid heads mount.
How to tell them apart
- A two-part lens: a Komura 300 mm f/5 head with a preset diaphragm and a 67 mm filter thread, and a separate Komura Unihelicoid focusing mount that carries the Bronica large bayonet; the mount is engraved II or III, and that engraving, not the head, decides which bodies it fits
- The Unihelicoid II/III mounts the large body bayonet directly, with the Bronica's own focusing unit removed; on a camera it sits where the 105 mm leaf-shutter Nikkor and the Nikon tele focusing units sit, not on the small front bayonet of the standard lenses
- Not Bronica's Zenzanon 300mm f/4.5 or Nikon's Nikkor-P·C 300mm f/5.6 for the same bodies, which carry their makers' names; not a Komura 300mm f/5 on a 39 mm Unidapter thread, which is the 35 mm-format lens
Komura 300mm f/5 head on Unihelicoid II (new large bayonet, Bronica C and later):
- A preset 300 mm lens head on a Komura focusing mount engraved Unihelicoid II, which fits the large body bayonet introduced with the Bronica C in December 1964 and kept through the C2, S2, S2A, EC, EC-TL and EC-TL II (Japanese Wikipedia)
Komura 300mm f/5 head on Unihelicoid III (old large bayonet, Bronica Z/D and S):
- The same head on a focusing mount engraved Unihelicoid III, for the old large bayonet of the Zenza Bronica Z/D and S, which the new large bayonet of the C and later does not accept (Japanese Wikipedia)
- Komura 300mm f/5 head on Unihelicoid II (new large bayonet, Bronica C and later): Japanese Wikipedia says the 300, 400 and 500 mm heads were each sold in two versions, Unihelicoid II for the newer large bayonet and Unihelicoid III for the older one. The same Unihelicoid takes all three heads, so a Bronica owner bought one focusing mount and the heads separately; a Komura adapter also put the heads on the Rollei SL66. No source read for this page dates either Unihelicoid or gives a price.
- Komura 300mm f/5 head on Unihelicoid III (old large bayonet, Bronica Z/D and S): Known from Japanese Wikipedia alone: the version for the old large bayonet of the first Bronicas. Which bodies the old-bayonet mount served is given by the bayonet itself, since the Z/D and S carry the earlier standard; Monaghan's note on an owner's 500 mm head lists the S among the bodies the Unihelicoid fits.
Specifications
- Formula
- Long-focus lens head, 4 elements in 3 groups
- Construction
- 4 elements / 3 groups
- Aperture range
- f/5
- Filter
- 67 mm
- Years manufactured
- 1965
- 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.
History
The Komura 300mm f/5 is the shortest of three long-focus lens heads that Sankyo Koki made for the focal-plane Zenza Bronica, sold to be used on the maker’s own Unihelicoid focusing mount rather than on the camera’s focusing unit. The scheme mirrors Nikon’s for the Bronica: the body’s helicoid comes off, exposing the large bayonet on the body itself, and a focusing mount carrying that bayonet takes an interchangeable head. Komura’s heads were 300, 400 and 500 mm, all on the same Unihelicoid, so an owner bought one mount and as many heads as wanted. Japanese Wikipedia gives the 300 as four elements in three groups, with a preset diaphragm and a 67 mm screw-in filter thread, and says it was sold in two versions: on the Unihelicoid II, for the large bayonet introduced with the Bronica C of December 1964 and carried by every later focal-plane body, and on the Unihelicoid III, for the older large bayonet of the Zenza Bronica Z/D and S, which the new one does not accept. camera-wiki’s list marks it “focus mod II”, a term the page does not explain.
Dates, prices and weights are not recorded in any source read for this page. The mid-1960s placing rests on the Unihelicoid II’s existence for the 1964 bayonet and on the 1965 EPOI dealer catalogue reproduced by Mike Eckman, which already lists some forty Komura lenses from 28 mm to 800 mm. The heads had a life beyond the Bronica: a Komura adapter put them on the Rollei SL66, and the lenses were later offered as head, helicoid and mount under the name Komuranon System 67/35, for the Asahi Pentax 6×7, the Rollei SL66 and various 35 mm SLRs. Whether the Komuranon 300 of that system is the same four-element glass is not stated. The 2× Telemore 66 converter that Komura made for the Bronica is no help here: it sits between body and focusing unit, and Japanese Wikipedia says it cannot be used with lenses that mount directly on the body bayonet, which is exactly how the Unihelicoid heads mount.
No review of the Bronica head has been found. Sankyo Koki also sold a 300mm f/5 Komura for 35 mm cameras on its 39 mm Unidapter mount, and the forum opinions of that lens, like Mike Eckman’s test of the 35 mm-format 500mm f/7, concern a different barrel and cannot be read across. A buyer should establish first which Unihelicoid the lens comes on, since a III will not go on an S2 or EC and a II will not go on an S; then that the preset ring and the helicoid turn freely, that the 67 mm thread is clean, and that the head’s bayonet into the Unihelicoid locks. A head without a Unihelicoid is of little use on a Bronica.
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 Komura 300mm f/5 (Bronica, Unihelicoid)? We'd love to feature it (with credit).
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