US 3,975,089, sole example — Ellis I. Betensky
| 12 ELEMENTS / 9 GROUPS |
| f ≈ 38.5–89.1 mm (patent: 36–83 mm) |
| F/2.8 |
| 2ω ≈ 58.7°–27.3° |
| ALL SPHERICAL |
Unit focus — all four groups move together on the focusing thread (patent col. 4); one push-pull ring zooms and focuses. Close-focus states use a single 11.18 mm extension calculated to reach the production 0.26 m (film plane) at 35 mm; the same extension gives ≈0.885 m at 85 mm (published 0.9 m).
| Element | Type | Glass |
|---|---|---|
| L1 | Negative Meniscus | SF6 (Schott) |
| L2 | Biconvex Positive | BSC6 (HOYA catalog-equivalent; production supplier unspecified) |
| L3 | Positive Meniscus | S-LAL13 (Ohara) |
| L4 | Biconvex Positive | SF57 (Schott) |
| L5 | Biconcave Negative | 834373 — dense flint (M-NBFD10 catalog match; LaSF5/S-LAH60 class) |
| L6 | Biconcave Negative | BSL3 (OHARA catalog equivalent; production supplier unspecified) |
| L7 | Biconvex Positive | SF11 (Schott) |
| L8 | Biconvex Positive | SK16 (Schott) |
| L9 | Positive Meniscus | FK5 (Schott) |
| L10 | Negative Meniscus | SF6 (Schott) |
| L11 | Biconvex Positive | BAF12 (SUMITA catalog-equivalent; production supplier unspecified) |
| L12 | Negative Meniscus | SF6 (Schott) |