Flor 50mm f/1.5

SOM Berthiot · LTM + Leica M + Other · 1940

our own finding

Also known as: SOM Berthiot Flor 50mm f/1.5 · SOM Berthiot Flor 50mm f1.5 · Som Berthiot Flor 1.5/50mm · S.O.M. Berthiot Flor 50mm f/1.5 · Berthiot Flor 50mm f/1.5 · Berthiot Flor 5cm f/1.5 · Flor-Berthiot 50mm f/1.5 · Berthiot Flor 1:1.5 F=5cm · Berthiot Flor 1:1.5 F=50mm · Flor 1:1.5 F=50 · Flor 50mm f1.5 · サン・ベルチオフロール 50mm F1.5

Variants & identification

Variant	Mount	Years	Serial ranges	Production
No. 412707, lens head in a modern Leica M helicoid	Leica M (later conversion: Hawk's Factory helicoid, made in Taiwan)	—	412707 (Leitz Photographica Auction 49, lot 323)	—
Leica screw mount by R. Lemasson, Paris	Leica M39 (rangefinder-coupled mount by R. Lemasson, Paris)	—	443307 (Leitz Photographica Auction 34, lot 219)	—
No-iris, fixed-focus head on a hand-built 24×24 camera	Fixed in a hand-built French X-ray camera prototype (24×24mm on 35mm film)	—	274297 (Leitz Photographica Auction 44, lot 309)	—

One lens or two. Berthiot made an f/1.5 Flor engraved F=50 and another engraved F=55. No source treats them as one design marked two ways, and the one source that discusses both, oldlens.com, says it is not clear why both exist: it reads the 55mm as computed a little longer, mostly for reflex cameras (Rectaflex, Exakta, M42), and notes that some Berthiot catalogues draw the 50mm f/1.5 as seven elements in five groups with the last group split in two, unlike the arrangement it reads for the f/2 and the 55mm, so it calls the construction hard to pin down. The auction lots are consistent with two lenses without proving it: every reflex mount seen is on a 55mm, and none of the 50mm lots is in a mount Berthiot supplied for a camera. Front-ring finish is no guide, since 50mm heads and 1950s 55mm heads both have chrome rings. This page and the 55mm page are kept apart until a catalogue or a measured example shows them to be one design.
Market. The 55mm in an original Leica mount has made €78,000 at Leitz (Auction 40); the 50mm examples have sold for €21,600 and €28,800 and are estimated at €20,000–24,000 in Auction 49.
Year. No launch year is published. 1940 is the earliest decade a source gives for an example (Leitz, no. 274297), not a launch date.

How to tell them apart (expand)

Engraved F=50 on the front ring; the f/1.5 Flor engraved F=55 is a different lens with its own page
Chrome lens head with SOM BERTHIOT PARIS and the serial number on the front ring; Bté (breveté, patented) follows the focal length on no. 412707
No factory Leica-mount example is documented: every one seen at auction is a head in someone else's mount

No. 412707, lens head in a modern Leica M helicoid:

Chrome lens head engraved 'FLOR 1:1.5 F=50 Bté', the serial number and 'SOM BERTHIOT PARIS', with its own knurled aperture ring scaled from 1.5 (Leitz lot photographs)
Black modern helicoid engraved 'S-50 HAWK'S FACTORY HELICOID MADE IN TAIWAN', with a metre scale from 0.7 m to infinity, a Leica-style depth-of-field scale and an M bayonet with a brass coupling ring (Leitz lot photographs)

Leica screw mount by R. Lemasson, Paris:

Focusing mount engraved 'R. LEMASSON Paris BREVETS S.G.D.G.', with a depth-of-field scale, a distance scale and a knurled grip at the rear (Leitz lot photograph)
Chrome head engraved 'FLOR 1:1.5 F=50 Bté 443307 SOM …', with an aperture ring marked 1:1.5 (engraved '1:15'), 2, 2.8, 4, 5.6 (Leitz lot photographs)

No-iris, fixed-focus head on a hand-built 24×24 camera:

No iris and no focusing: the head is fixed in a long chrome tube on the camera's front plate (Leitz lot text and photograph)
Chrome front ring engraved '…RIOT PARIS FLOR …' and '…5 F=50 Bté 274297' (Leitz lot photographs)

No. 412707, lens head in a modern Leica M helicoid: Offered at Leitz Photographica Auction 49, lot 323, sale 28 November 2026: estimate €20,000–24,000, starting price €10,000, no bids recorded on 9 November 2026. Leitz grades it B/A, calls it 'extremely rare', 'professionally adapted for Leica M mount, RF coupled', with uncoated optics showing some cleaning marks, both caps and a modern metal hood, and gives the manufacture year as 1930s (see the dating note below). The lot photographs show what the adaptation is: the original lens head screwed into a current Taiwanese focusing helicoid. It is a recent conversion, not a period one, and nothing of the original focusing mount comes with it.
Leica screw mount by R. Lemasson, Paris: Sold at Leitz Photographica Auction 34, lot 219, for €28,800 including buyer's premium, against an estimate of €16,000–20,000 and a starting price of €8,000. Leitz grades it B/A, dates it to the 1950s and describes the mount as an 'early 1950's conversion by French manufacturer R. Lemasson Paris', rangefinder-coupled; it came with a rear cap and a hood marked BOUM PARIS. Camera-wiki reproduces an advertisement by Roger Lemasson in Photo Cinéma, April 1946, for a Berthiot 100mm f/2 'apparently with a mount fitting either Leica or Contax', so a Paris workshop of that name was mounting Berthiot lenses for 35mm rangefinders in the period. Leitz's description makes this a period conversion, not a Berthiot factory mount.
No-iris, fixed-focus head on a hand-built 24×24 camera: Sold at Leitz Photographica Auction 44, lot 309, for €21,600 including buyer's premium, against an estimate of €20,000–24,000 and a starting price of €10,000. Leitz grades it B+, dates it to the 1940s, and describes it as 'no iris and fixed focus', with light haze and cleaning marks on the front element, 'mounted on an interesting X-ray camera prototype or unique piece entirely hand-made by a very skilled mechanic (France), 24x24mm on standard 35mm film'. Whether the head left Berthiot without an iris or lost it in the conversion is not recorded.

Serial-range notes

274297, 412707, 443307: Berthiot numbered its lenses in one sequence across types, so the numbers date the 50mm f/1.5 only against other Berthiot lenses. Leitz dates 274297 to the 1940s and 443307 to the 1950s, but 412707 to the 1930s, which puts it before a lower number. An f/1.5 55mm Flor, no. 283946, is dated c.1940–42 by its owner at oldlens.com, and Leitz dates the 55mm no. 283935 to the 1940s. Against those points 412707 is more likely a 1940s lens than a 1930s one; Leitz's date is given as Leitz gives it.

Specifications

Formula: Modified double Gauss, apparently seven elements in five groups with a rear group of Berthiot's own form; a Berthiot catalogue drawing shows the 50mm f/1.5 with the last group split instead, so the arrangement is not settled (oldlens.com)
Aperture range: f/1.5
Country: France

What reviewers say

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History

The f/1.5 Flor engraved F=50 is the rarer and the less explained of Berthiot’s two fast Flors. It is a fast double-Gauss derivative, seven elements in five groups by the reading of the one source that has compared the line, though a Berthiot catalogue drawing of this lens shows a split last group and the point is open. Berthiot named its anastigmats Flor from about 1921, and the f/1.5s are the fastest of the name. The owner who writes oldlens.com, who has the 55mm, notes that this one almost never reaches the market and that no advertisement shows it fitted to a camera. He suggests it may hardly have been sold to the public at all.

The examples that have surfaced bear that out. Each is a lens head in someone else’s mount. One, with no iris and fixed focus, is built into a hand-made French 24×24 camera that Leitz describes as an X-ray camera prototype. Another is in a rangefinder-coupled Leica screw mount made in the early 1950s by R. Lemasson of Paris; a Roger Lemasson advertised a Berthiot 100mm f/2, apparently in a Leica or Contax mount, in 1946. The one in Auction 49 is described as ‘professionally adapted for Leica M’. Its photographs show the original head screwed into a current Hawk’s Factory helicoid made in Taiwan. That makes the Leica M version a recent conversion, not anything Berthiot or a period workshop made, and the Lemasson lens is a period conversion. No source records a 50mm f/1.5 that left Berthiot in a Leica mount.

The F=55 lens is treated on its own page. It comes in more factory mounts, among them Leica thread with an A. Garneau coupling, Exakta, Praktiflex and Rectaflex. oldlens.com reads it as computed slightly longer for reflex cameras, and no source says the two are one design. The two lenses also sell differently: the 55mm has made €78,000 in an original Leica mount, while the 50mm heads have sold for €21,600 and €28,800.

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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

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