US 3,975,089 Example 1 — Betensky / Ponder & Best
| 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 — entire optical assembly translates. Push-pull zoom/focus ring.
| Element | Type | Glass |
|---|---|---|
| L1 | Negative Meniscus | SF6 (Schott) |
| L2 | Biconvex Positive | 531621 — BSM-type crown (no exact public catalog match) |
| 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 | 498651 — BK3-type borosilicate crown (no exact public catalog match) |
| L7 | Biconvex Positive | SF11 (Schott) |
| L8 | Biconvex Positive | SK16 (Schott) |
| L9 | Positive Meniscus | FK5 (Schott) |
| L10 | Negative Meniscus | SF6 (Schott) |
| L11 | Biconvex Positive | 639451 — BaSF52-type barium dense flint (no exact public catalog match) |
| L12 | Negative Meniscus | SF6 (Schott) |
Detailed analysis available in the interactive viewer above.