JP H04-255813 A, Numerical Example 1 — Hiroshi Endo
| 8 ELEMENTS / 6 GROUPS |
| DESIGN f = 100 mm |
| DESIGN F/2.0 |
| ALL SPHERICAL |
| INNER FOCUS |
Inner focus, which Canon calls rear focusing: group 2 moves toward the image while the stop and groups 1 and 3 stay put. The patent prints D9 and D12 only at infinity (2.66 and 24.99 mm). The near gaps here are solved, not printed: at Canon's 0.9 m minimum focus, D9 is 16.487 mm and D12 is 11.163 mm, a 13.83 mm stroke at 0.139× (Canon states 0.14×). The same solve at 1 m, measured from the image plane, gives f/2.27 and +2.8% distortion at 21.3 mm image height, against f/2.3 and about +2.8% at the top of the patent's Fig. 4(B).
| Element | Type | Glass |
|---|---|---|
| L1 | Biconvex Positive | S-BAL50 (OHARA catalog equivalent; production supplier unspecified) |
| L2 | Positive Meniscus | S-LAL7 (OHARA catalog equivalent; production supplier unspecified) |
| L3 | Positive Meniscus | S-LAH51 (OHARA catalog equivalent; production supplier unspecified) |
| L4 | Negative Meniscus | TPH55 (OHARA catalog equivalent; production supplier unspecified) |
| L5 | Positive Meniscus | SF6 (Schott catalog equivalent; production supplier unspecified) |
| L6 | Biconcave Negative | S-BAL50 (OHARA catalog equivalent; production supplier unspecified) |
| L7 | Negative Meniscus | SF6 (Schott catalog equivalent; production supplier unspecified) |
| L8 | Biconvex Positive | S-LAH51 (OHARA catalog equivalent; production supplier unspecified) |