US 4,303,314, Embodiment 1 — Sei Matsui
| 4 elements / 4 groups |
| f = 100.02 mm |
| F/2.8 |
| 2ω = 24° patent |
| 0 aspherical surfaces |
Unit focusing by whole-lens extension; patent gives only infinity spacing, so close focus varies only the final BFD.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | BACD4 (HOYA compatible spectral proxy; source nd=1.61272, νd=58.6; supplier unspecified) |
| L2 | Positive Meniscus | S-BSM16 (OHARA compatible spectral proxy; supplier unspecified) |
| L3 | Negative Meniscus | S-TIH1 (OHARA compatible spectral proxy; supplier unspecified) |
| L4 | Positive Meniscus | S-TIH13 (OHARA compatible spectral proxy; supplier unspecified) |