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

Biotar 4cm f/2

Carl Zeiss · Contax RF · 1932 · Biotar — a double Gauss, unlike the Sonnars around it

single source, unconfirmed

Also known as: Zeiss Biotar 40mm f/2 · Biotar 4cm f2

Variants & identification

Variant Mount Years Serial ranges Production
Biotar 4cm f/2 Contax RF 1932–1945 — No figure published; camera-wiki calls it rare
Biotar 4¼cm f/2 Contax RF 1936–1945 — No figure published; also described as rare
  1. Production totals from Pacific Rim Camera, which the variant table does not carry and camera-wiki does not quantify: fewer than 400 lenses marked 4cm and 250 marked 4¼cm — under 650 in all, which is why both versions are called rare.
  2. Pacific Rim Camera dates the lens 1933–1938, introduced in black and nickel and discontinued in 1938. The variant table here runs 1932–1945 for the 4cm and 1936–1945 for the 4¼cm. Both are recorded; no serial evidence has been found that would settle either end.
  3. Pacific Rim Camera also reports that the 1936 relabelling was 4cm to 4-1/2cm 'or occasionally 4.25cm' — its own text gives two different figures for the same change, while its production count uses 4-1/4cm. The variant table's 4¼cm follows the count.
  4. The 4¼cm reading gains outside support. English Wikipedia's list of lenses for the original Contax rangefinder models gives the lens as Biotar 42.5/2.0, which agrees with 4¼cm and not with the 4-1/2cm Pacific Rim Camera also prints.
  5. The one-lens-or-two question is answered, from Zeiss Ikon's own price lists. English Wikipedia lists a Biotar 40/2.0 and a Biotar 42.5/2.0 as separate entries in the Contax lineup, which reads as two lenses; Pacific Rim Camera describes 1936 as a relabelling with no optical change, which is one lens renamed. The maker's American price lists support Pacific Rim, in two ways. First, no list carries both: Price List No. 14 offers a single "Biotar F/2, 4 cm" at $96.00, and Price List No. 15 of 1 May 1939 and No. 16 of 1 October 1941 each offer a single "Biotar f/2 - 4.25 cm" at $111.00. At no date does Zeiss Ikon sell two Biotars. Second, and more tellingly, the accessory that serves the lens never changes its part number across the rename: the wide-angle finder is Zeiss Ikon 432/4 for the "Biotar F/2, 4 cm" in the earlier list and Zeiss Ikon 432/4 for the "Biotar f/2 - 4.25 cm" in 1939 and again in 1941. A genuinely new focal length would need a new finder mask and a new catalogue number. One lens, renamed in the middle of its life, and the variant table above should be read as two periods of one optic rather than as two products.
  6. Partial corroboration, and the badge stays. English Wikipedia lists a Biotar 40/2.0 and a Biotar 42.5/2.0 as separate entries in the original rangefinder lineup, independently of camera-wiki, so the two-lens shape of the variant table is now carried by more than one source. The figures that make up most of this entry are not: the production counts of fewer than 400 and 250, the four-batch finish sequence and the 1936 relabelling remain Pacific Rim Camera's alone. Zeiss Ikon VEB's history of the Biotar line was checked and covers the 1927 f/1.4 and the 58mm designs without reaching the Contax 4cm.
How to tell them apart (expand)
  • A double-Gauss design in a system built on Sonnars
  • 40mm, between the standard 50 and the wide 35

Biotar 4cm f/2:

  • Black and nickel at the time of the Contax I; chrome later

Biotar 4¼cm f/2:

  • Engraved 4,25cm where the earlier barrel reads 4cm. The same optic under a later name, not a second lens — see the table notes

Serial-range notes

the whole number
How to date one. Carl Zeiss drew every photographic lens number from a single running sequence covering all models at once, so a Zeiss lens is dated by reading its number off a serial/year table rather than by counting within its own type — there is no per-model list of the Leitz kind. The table, taken from Wilkinson and Glanfield's A Lens Collector's Vade Mecum, runs the Jena sequence from 173,418 in 1912 to about 2,900,000 in 1942; camera-wiki and Craig Camera publish near-identical copies of it. The 1912 opening is given here as Craig Camera and the Leica Contax blog print it. Camera-wiki transposes it to 137,418, which the Vade Mecum's own quantity column rules out — the blog's copy of the 1912 row reads "173,418 - 200,520 27,102", and only the first reading subtracts to the published 27,102.
1364483–2900000
The Jena year boundaries that bracket this lens's production, from camera-wiki: 1932 = 1,364,483–1,389,279; 1933 = 1,436,671–1,456,003; 1934 = 1,500,474–1,590,000; 1935 = 1,615,764–1,752,303; 1936 = 1,674,882–1,942,806; 1937 = 1,930,150–2,219,775; 1938 = 2,267,991–2,527,984; 1939 = 2,527,999–2,651,211; 1940 = 2,652,000–2,678,000; 1941 = 2,678,326–2,790,346; 1942 = 2,800,000–2,900,000. The table stops at 1942, so anything later cannot be dated from the running number alone.
the engraved focal length
The sharpest date line on this lens, and it is not a number. Pacific Rim Camera reports that in 1936 Zeiss changed the engraving from 4cm to 4¼cm (occasionally 4.25cm) without changing the optics — a relabelling, probably to sit the lens more evenly between the new 3.5cm Biogon and the 5cm Sonnars. A barrel marked 4cm is therefore the earlier production and one marked 4¼cm the later, whatever the serial says.
the barrel finish
The batch sequence Pacific Rim Camera gives, in place of serials: black and nickel with a nickel-plated depth-of-field scale and no filter thread (first batch, 1933); the same with the scale in black paint (second batch, 1934); chrome, with the inner aperture ring chrome and black-filled numbers (third batch, 1935); then from 1936 a black aperture ring with white numbers and a 40.5mm filter thread.
any number near a year boundary
Blocks were allotted to production in sequence, but batches were not always finished in block order, so the published year ranges overlap — 1935 runs to 1,752,303 while 1936 opens at 1,674,882 — and a serial places a lens within a year or two rather than to a month. Pentacon Six sets out the mechanism and points to Hartmut Thiele's Fabrikationsbuch Photooptik, a transcription of the factory books, for batch-level dates.
above 3000000 (Jena) against 10000–3000000 (Oberkochen)
Why a Zeiss number needs a factory before it needs a table. After 1945 the sequence forks: Carl Zeiss Jena in the East carried the old numbers on from 3,000,000, while Carl Zeiss Oberkochen in the West began a fresh sequence at 10,000 in 1946 — 10,000–500,000 = 1946–51, 500,000–1,100,000 = 1951–53, 1,100,000–2,600,000 = 1953–59. This lens is prewar Jena only and never carried an Oberkochen number, but the fork is what makes a six-figure Zeiss number ambiguous in general: 1920s in Jena, early 1950s in Oberkochen.
a letter followed by five digits
Not a lens number at all. That is the Zeiss Ikon CAMERA sequence, inherited from ICA in 1909, which rolls to the next letter at 99,999, reached Z in 1936 and restarted at A. A Contax body number and a Zeiss lens number belong to separate schemes and must never be read against the same table.
no serial list has been published for this lens
No source consulted publishes serial ranges or batch blocks for the Biotar in either marking. Pacific Rim Camera, which prints batch numbers for the 50mm, 85mm and 135mm Contax lenses, gives none for the Biotar. A copy is dated from the general Jena table above and placed within the run by its finish and its engraved focal length.

Specifications

Formula
Biotar — a double Gauss, unlike the Sonnars around it
Construction
6 elements / 4 groups
Aperture range
f/2
Weight
260 g
Filter
40.5 mm
Years manufactured
1932–1945
Country
Germany

What reviewers say

History

The Biotar is the exception in the Contax catalogue: a double Gauss, the design family the Sonnar was invented to beat, at 40mm — a focal length no other rangefinder system offered until the Leica CL of 1973.

camera-wiki lists it twice, as a 4cm f/2 and a 4¼cm f/2, and calls both rare without giving a figure for either; English Wikipedia likewise gives a 40/2.0 and a 42.5/2.0 as separate entries. Whether the second is a revision or a separate lens neither of them says.

Zeiss Ikon’s price lists do. There is only ever one Biotar in the catalogue — 4 cm at $96.00 in the earlier list, 4.25 cm at $111.00 in May 1939 and again in October 1941 — and the wide-angle finder sold for it keeps the same catalogue number, 432/4, on both sides of the change of name. A new focal length would have taken a new finder and a new number. The two entries in the wikis are one lens, relabelled, which is what Pacific Rim Camera says happened in 1936.

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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 Biotar 4cm f/2? We'd love to feature it (with credit).

Live listings

Asking price, USD: a median of $450 across 7 fixed-price listings on 2026-09-06 (middle half $300–$450). First day tracked.

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

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Listings updated 2026-09-05. Links go to the shop or marketplace that carries the item.

Related: Biotar 7.5cm f/1.5 · Sonnar 5cm f/2

Sources (11)

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.