US 4,189,212 Example 8 — Nippon Kogaku wide-angle zoom
| 25-50 mm f/4 |
| 11 elements / 10 groups |
| Two-group negative-positive wide-angle zoom |
| All-spherical prescription |
| Nikon F mount / 135 full-frame |
Unit-focus manual helicoid. Close-focus back-focus values are approximated from the published 0.6 m minimum focus distance because the patent publishes only infinity-focus spacings.
| Element | Type | Glass |
|---|---|---|
| L1 | Negative Meniscus | Unmatched 773/494 (near Hoya M-TAF1 / Ohara S-LAH66N) |
| L2 | Positive Meniscus | F5 (Schott) / S-TIM5 (Ohara) |
| L3 | Biconcave Negative | S-LAH65V class (Ohara, near 804/466) |
| L4 | Positive Meniscus | SF6 (Schott) / S-TIH6 (Ohara) |
| L5a | Biconvex Positive | S-TIL6 (Ohara) / LLF6 class |
| L5b | Negative Meniscus | SF6 (Schott) / S-TIH6 (Ohara) |
| L6 | Positive Meniscus | K10 class (501/565) |
| L7 | Positive Meniscus | K10 class (501/565) |
| L8 | Negative Meniscus | J-LAFH3 class (Hikari, close 795/284) |
| L9a | Biconvex Positive | Unmatched 465/658 (FK/phosphate crown class) |
| L9b | Biconvex Positive | K10 class (501/565) |
Detailed analysis available in the interactive viewer above.