Table of Contents
Pentax-A 645 SMC 45mm f/2.8
Summary
The SMC Pentax-A 645 45mm f/2.8 is a compact, manual-focus wide-angle prime introduced in 1984 for the Pentax 645 medium format system. With a field of view equivalent to ~28–30mm on 35mm film, it’s designed for landscape, street, and environmental portraiture, offering a fast aperture and lightweight build for handheld shooting. Optically, it features a 9-element/8-group design with Super Multi-Coating (SMC), an 8-blade automatic diaphragm, and a minimum aperture of f/22. It focuses down to 45cm, delivers 0.15× magnification, and uses a 67mm filter thread. The lens weighs 400g, measures 74 × 66.5mm, and includes a dedicated screw-in hood (RH-RA 70mm) and soft case (S80-120). It has an “A” setting on the aperture ring, enabling full automation on modern Pentax 645 bodies.
Tech Specs
| Manufacturer | Pentax |
| Series | Pentax-A |
| Model | 645 SMC |
| Focal Length | 45mm |
| Max Aperture | f/2.8 |
| Min Aperture | f/22 |
| Format | 645 film |
| Image Circle | - |
| Minimum Focus | 45cm |
| Focus Rotation | ° |
| Iris Blades | 8 |
| Optical Design | 9/8 |
| Squeeze | none |
| Front Diameter | 74mm |
| Filter Thread | 67mm |
| Focus/Zoom Rod | none |
| Native Mount | Pentax 645 |
| Data Protocol | none |
| Length | 66.5mm |
| Weight | 400g |
| Body Telescope | - |
| Body Material | - |
| Focus Drive | - |
| Iris Drive | - |
| Zoom Drive | - |
History
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