Table of Contents
Pentax-A 645 SMC 45-85mm f/4.5
Summary
The SMC Pentax-A 645 45–85mm f/4.5 is a manual-focus standard zoom introduced in the mid-1980s for the Pentax 645 medium format system. Covering a focal range equivalent to approximately 35–66mm in 35mm terms, it was designed to replace three primes—45mm, 55mm, and 75mm—in a single, versatile package. It shares its optical formula with the later FA version but retains full manual focus and aperture control, with an “A” setting for Program and Shutter-Priority automation on compatible bodies. Optically, it features an 11-element - 9-group design with Super Multi-Coating (SMC) and an 8-blade automatic diaphragm. The lens stops down to f/32, focuses as close as 50cm, and delivers a 0.22× magnification ratio—making it surprisingly capable for close-up work. It uses a 77mm filter thread, weighs 805g, and measures 79 × 99mm. It lacks internal focusing or weather sealing, but includes a manual aperture ring, a dedicated RH-RD77 screw-in hood, and was typically sold with a clip-on cap and soft case.
Tech Specs
| Manufacturer | Pentax |
| Series | Pentax-A |
| Model | 645 SMC |
| Focal Length | 45-85mm |
| Max Aperture | f/4.5 |
| Min Aperture | f/32 |
| Format | 645 film |
| Image Circle | - |
| Minimum Focus | 50cm |
| Focus Rotation | ° |
| Iris Blades | 8 |
| Optical Design | 11/9 |
| Squeeze | none |
| Front Diameter | 79mm |
| Filter Thread | 77mm |
| Focus/Zoom Rod | none |
| Native Mount | Pentax 645 |
| Data Protocol | none |
| Length | 99mm |
| Weight | 805g |
| Body Telescope | - |
| Body Material | - |
| Focus Drive | - |
| Iris Drive | - |
| Zoom Drive | - |
History
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