US 3,942,876, Table IV — Ellis I. Betensky
| 6 elements / 6 groups |
| Sonnar-type telephoto with fixed rear corrector |
| All-spherical design |
| MFD 1.2 m (1:4 repro ratio) |
| 72 mm filter thread |
Front objective L1–L5 translates objectward as a rigid unit; rear corrector L6 stays fixed to the mount and film plane. One variable gap: 3.2 mm (infinity), 15.0 mm (patent close row), 33.8 mm calculated for the 1.2 m production MFD.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | 569631 — PSK2 phosphate crown (Schott) |
| L2 | Positive Meniscus | BSC7 (HOYA) / N-BK7 (Schott) |
| L3 | Biconcave Negative | SF6 (Schott) / S-TIH6 (OHARA) |
| L4 | Positive Meniscus | SF6 (Schott) / S-TIH6 (OHARA) |
| L5 | Negative Meniscus | LAFL4 (HOYA catalog-equivalent; production supplier unspecified) |
| L6 | Negative Meniscus | N-BALF4 (Schott; BaLF4-class equivalent) |