US 4,764,000 Example 8 — Minolta / Tokumaru
| 8 elements / 8 groups |
| f = 100.0 mm design |
| F/2.83 design; marketed f/2.8 |
| 1:1 macro, 0.35 m MFD |
| All-spherical floating-focus macro |
Three-group floating focus: Groups I and III move together toward the object, while the negative Group II moves in the same direction by a smaller amount; D8 increases, D12 decreases, and BF lengthens to the β = -1.0 close-focus state.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | S-NSL3-class crown (OHARA 518590; inferred) |
| L2 | Positive Meniscus | S-LAL9-class lanthanum crown (OHARA 691548; inferred) |
| L3 | Positive Meniscus | S-LAL9-class lanthanum crown (OHARA 691548; inferred) |
| L4 | Negative Meniscus | BPH50 (OHARA) |
| L5 | Negative Meniscus | H-LAK12 (CDGM equivalent; patent 697565) |
| L6 | Positive Meniscus | S-LAH60-class dense lanthanum flint (OHARA 834372; inferred) |
| L7 | Negative Meniscus | 807316 - dense lanthanum flint (patent nd=1.80741, vd=31.59; unresolved) |
| L8 | Biconvex Positive | S-BAL35-class barium crown (OHARA 589612; inferred) |
Detailed analysis available in the interactive viewer above.