US 4,189,212, Example 8 — Norio Mizutani, Soichi Nakamura
| 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 | M-TAF1 (Hoya catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L2 | Positive Meniscus | S-TIM5 (Ohara catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L3 | Biconcave Negative | S-LAH65V (Ohara catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L4 | Positive Meniscus | S-TIH6 (Ohara catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L5a | Biconvex Positive | S-TIL6 (Ohara catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L5b | Negative Meniscus | S-TIH6 (Ohara catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L6 | Positive Meniscus | K10 (Schott catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L7 | Positive Meniscus | K10 (Schott catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L8 | Negative Meniscus | J-LAFH3 (Hikari catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L9a | Biconvex Positive | FC3 (Hoya catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |
| L9b | Biconvex Positive | K10 (Schott catalog spectral proxy; patent nd/vd retained; production supplier unspecified) |