US 4,518,229 Example 8 — Minolta / Yasukuni
| Patent Example 8: f = 295.0 mm, FN = 2.9 |
| Marketed as 300mm f/2.8 |
| 10 prescription elements / 8 groups |
| 11 / 9 production count includes rear filter |
| Inner focus to patent 3 m endpoint |
| All spherical surfaces |
Inner focus by image-side translation of subunit II-2 (L6-L8). Patent Table 9 gives 11.760 mm travel for a 3 m object distance; production MFD is 2.5 m but is not tabulated in the patent.
| Element | Type | Glass |
|---|---|---|
| L1 | Biconvex Positive | 495797 - fluorophosphate ED-class crown (catalog unresolved; not S-FPL51) |
| L2 | Biconvex Positive | 495797 - fluorophosphate ED-class crown (catalog unresolved; not S-FPL51) |
| L3 | Biconcave Negative | 682366 - dense flint class (catalog unresolved) |
| L4 | Negative Meniscus | 654339 - dense flint class (Hikari SF9 public code match) |
| L5 | Positive Meniscus | S-BSM14 class (OHARA; close vintage 603/607 match) |
| L6 | Positive Meniscus | S-TIH1 class (OHARA; close vintage 717/295 match) |
| L7 | Biconcave Negative | S-BSM14 class (OHARA; close vintage 603/607 match) |
| L8 | Biconcave Negative | 670571 - high-index crown / lanthanum-crown class (catalog unresolved) |
| L9 | Biconvex Positive | S-BSM14 class (OHARA; close vintage 603/607 match) |
| L10 | Negative Meniscus | 654339 - dense flint class (Hikari SF9 public code match) |
Detailed analysis available in the interactive viewer above.