Table of Contents
Pentax-A SMC 100mm f/4 Macro
Summary
The SMC Pentax-A 100mm f/4 Macro is a manual-focus macro prime introduced in 1984 for the Pentax K-mount, and produced until 1989. It was designed as a compact, affordable alternative to faster macro lenses, offering 1:2 magnification without extension tubes. Though modest in aperture, it delivers excellent close-range performance, making it a favorite among vintage macro enthusiasts and collectors. Optically, it uses a 5-element, 3-group design with Super Multi-Coating (SMC) and a 6-blade automatic diaphragm, stopping down to f/32. The lens focuses as close as 45cm, yielding a 0.5× magnification ratio, and uses a 49mm filter thread. It weighs 340g, measures 65 × 78mm, and includes a manual aperture ring with an “A” setting, enabling full program and shutter-priority modes on compatible bodies. There’s no internal focusing or weather sealing, but the deeply recessed front element eliminates the need for a hood. A rare Dental Macro variant was also produced, featuring specialized distance markings for clinical photography.
Tech Specs
| Manufacturer | Pentax |
| Series | A Series Macro |
| Model | SMC |
| Focal Length | 100mm |
| Max Aperture | f/4 |
| Min Aperture | f/32 |
| Format | Full-Frame |
| Image Circle | - |
| Minimum Focus | 45cm |
| Focus Rotation | ° |
| Iris Blades | 6 |
| Optical Design | 5/3 |
| Squeeze | none |
| Front Diameter | 65mm |
| Filter Thread | 49mm |
| Focus/Zoom Rod | none |
| Native Mount | Pentax K |
| Data Protocol | none |
| Length | 78mm |
| Weight | 340g |
| Body Telescope | - |
| Body Material | - |
| Focus Drive | - |
| Iris Drive | - |
| Zoom Drive | - |
History
Country of Origin:
Release Date: 1984
Launch Price:
Design Revisions: