Pentax Prototype Prime Lenses
| Lens | Elements- Groups | Min. Focus Distance (m) | Filter Dia- meter (mm) | Lens Diameter x Length (mm) | Weight (g) |
|---|---|---|---|---|---|
| K 8.4/2.8 Bird's-Eye | 10-7 | — | — | unknown x unknown | unknown |
| K 20/1.4 AL | 11-10 | 0.25 | 77 | 80 x 65 | 445 |
| Takumar-DA 40/2.8 AL Limited | 5-4 | 0.4 | 49 | 63 x 15 | 90 |
| K 300/2 | unknown-unknown | unknown | 150 | unknown x unknown | 4500 |