Table of Contents
Pentax-A SMC 28-135mm f/4
Summary
The SMC Pentax-A 28–135mm f/4 is a manual-focus, full-frame zoom lens introduced in 1984 and produced until 1991, designed for K-mount film SLRs. It was one of the few Pentax zooms of the era to offer a constant f/4 aperture across its range, and it was positioned as a premium all-in-one solution for travel, landscape, and general-purpose photography. Optically, it features a 17-element - 15-group design with Super Multi-Coating (SMC) and a 6-blade automatic diaphragm. The lens stops down to f/22, focuses as close as 1.7 meters, and delivers a 0.33× magnification ratio—with a macro mode at 28mm that enables closer focusing for near-life-size detail. It uses a 77mm filter thread, weighs a hefty 820g, and measures 80 × 112mm. The lens includes a manual aperture ring with “A” setting, a rotating front element, and was typically sold with the RH-A80 hood and HE-169 hard case. It lacks internal focusing or weather sealing.
Tech Specs
| Manufacturer | Pentax |
| Series | A Series Zoom |
| Model | SMC |
| Focal Length | 28-135mm |
| Max Aperture | f/4 |
| Min Aperture | f/22 |
| Format | Full-Frame |
| Image Circle | - |
| Minimum Focus | 170cm |
| Focus Rotation | ° |
| Iris Blades | 6 |
| Optical Design | 17/15 |
| Squeeze | none |
| Front Diameter | 80mm |
| Filter Thread | 77mm |
| Focus/Zoom Rod | none |
| Native Mount | Pentax K |
| Data Protocol | none |
| Length | 112mm |
| Weight | 820g |
| Body Telescope | - |
| Body Material | - |
| Focus Drive | - |
| Iris Drive | - |
| Zoom Drive | - |
History
Country of Origin:
Release Date: 1984
Launch Price:
Design Revisions: