M 28/2.8 (version 2)

General Description
This lens is extremely interesting. Its lens mount is of the "original K-mount" type, and its name associates it undoubtedly with the M-series of K-mount lenses. On the other hand, the lens shares its most important characteristics with the later SMC-A lens: the linear aperture mechanism and the updated optical formula. Even the focusing ring is of the A-style.
Guesses can be made that in 1982 Pentax was already hard at work developing the A-series bodies and lenses, and when parts for the "original" M 28/2.8 lens were depleted, it was decided to switch to production of the new lens, but without exposing the externally visible A-series features — electrical contacts on the lens mount and "A" position on the aperture ring. Still, this lens with its low production numbers is a rather unique piece of K-mount history.
| Product Information | |
|---|---|
| Exact Name | smc PENTAX-M 1:2.8 28mm |
| Color | black |
| Year of Introduction | 1982 |
| Catalog Number | 22977 |
| Sold with Hood | — |
| Sold with Case | dedicated hard case: exact name unknown |
Technical Specifications
| Optics | |
|---|---|
| Optical Formula | 7 elements in 7 groups |
| Aperture Range | f/2.8 ~ f/22 |
| Number of Aperture Blades | 5 |
| Minimum Focusing Distance | 0.3 m |
| Maximum Magnification | 0.13 X |
| Mechanics | |
| Filter Diameter | 49 mm |
| Maximum Diameter | 63 mm |
| Length | 37 mm |
| Weight | 170 g |
| Accessories | |
| Cap | plastic clip-on cap, 49 mm |
| Fitting Hood(s) | clip-on hood: PH-S49 |
| Fitting Case(s) | dedicated hard case: exact name unknown |