JP1976-026535 — Toshiko Shimokura
| 8 ELEMENTS / 8 GROUPS |
| MODELED EFL 28.1585 mm |
| PATENT DESIGN f/2.0 |
| PATENT 2ω = 76° |
| MARKETED 28mm f/1.8 |
Production MFD is 0.18 m from the film plane. JP1976-026535 Example 1 publishes only an M=1/6 state in which L2–L4 shifts 0.9996 mm imageward; the complete focusing extension/cam to 0.18 m is not published, so no runtime internal focus reconstruction is authored.
| Element | Type | Glass |
|---|---|---|
| L1 | Negative Meniscus | S-BAL35 catalog-equivalent coefficient proxy (patent 589611; production supplier unspecified) |
| L2 | Biconvex Positive | E-FD2 catalog-equivalent coefficient proxy (patent 648338; production supplier unspecified) |
| L3 | Negative Meniscus | S-BAL35 catalog-equivalent coefficient proxy (patent 589611; production supplier unspecified) |
| L4 | Positive Meniscus | LAC10 catalog-equivalent coefficient proxy (patent 720503; production supplier unspecified) |
| L5 | Plano-Convex Positive | LAC8 catalog-equivalent coefficient proxy (patent 713539; production supplier unspecified) |
| L6 | Biconcave Negative | S-TIH6 catalog-equivalent coefficient proxy (patent 805254; production supplier unspecified) |
| L7 | Positive Meniscus | K-LaK14 catalog-equivalent coefficient proxy (patent 697557; production supplier unspecified) |
| L8 | Biconvex Positive | S-LAH51 catalog-equivalent coefficient proxy (patent 786442; production supplier unspecified) |