Table of Contents
Pentax SMC 300mm f/4
Summary
The SMC Pentax 300mm f/4 is a manual-focus telephoto prime introduced in 1975 and produced until 1981, designed for full-frame K-mount film cameras. It was Pentax’s first bayonet-mount 300mm lens and part of the original K-series, known for its robust build and optical ambition. Though later replaced by the more compact M* 300/4, the original K 300/4 remains a favorite among vintage lens enthusiasts for its solid construction, smooth focus, and distinct rendering. It features a 7-element - 5-group optical design, Super Multi-Coating (SMC), and an 8-blade automatic diaphragm. The lens stops down to f/32, focuses as close as 4 meters, and delivers 0.09× magnification. It uses a 77mm filter thread, weighs 1020g, and measures 85 × 188mm. It includes a built-in sliding hood, plastic clip-on cap, and was sold with a dedicated hard case. There’s no “A” setting on the aperture ring, so it’s best used in manual or aperture-priority modes. Unlike its Takumar predecessors, it lacks a tripod collar, which can make long exposures more challenging.
Tech Specs
| Manufacturer | Pentax |
| Series | K Series Prime |
| Model | SMC |
| Focal Length | 300mm |
| Max Aperture | f/4 |
| Min Aperture | f/32 |
| Format | Full-Frame |
| Image Circle | - |
| Minimum Focus | 400cm |
| Focus Rotation | ° |
| Iris Blades | 8 |
| Optical Design | 7/5 |
| Squeeze | none |
| Front Diameter | 85mm |
| Filter Thread | 77mm |
| Focus/Zoom Rod | none |
| Native Mount | Pentax K |
| Data Protocol | none |
| Length | 188mm |
| Weight | 1020g |
| Body Telescope | - |
| Body Material | - |
| Focus Drive | - |
| Iris Drive | - |
| Zoom Drive | - |
History
Country of Origin:
Release Date: 1975
Launch Price:
Design Revisions: