Pentax SMC Pentax-M 50mm f/1.4
The Pentax SMC Pentax-M 50mm f/1.4 is a 50mm f/1.4 manual-focus lens for the Pentax K mount, made by Pentax from 1977-1984. It uses 7 elements / 6 groups, Double Gauss. Typical used value is $60 to $210, with most examples near $110, and it adapts to Sony E, Fuji X, MFT, Canon RF, Nikon Z, and L-mount with a plain mechanical adapter.
Pentax SMC Pentax-M 50mm f/1.4 specifications
Pentax SMC Pentax-M 50mm f/1.4 specifications
Why collectors want it
A compact fast fifty in the K bayonet with the well regarded SMC multi-coating for good flare control. It renders with smooth bokeh and neutral color, sharpening nicely by f/2. It is one of the better value fast standard lenses.
Mount and adapters for the SMC Pentax-M 50mm f/1.4
The Pentax SMC Pentax-M 50mm f/1.4 has a native Pentax K mount. Pentax K is the 1975 bayonet that replaced M42 while keeping its 45.46mm register, and it remains in use on Pentax DSLRs today. Every mirrorless mount has a shorter register than 45.46mm, so a plain mechanical adapter puts the lens at its design distance and infinity focus is preserved. Plain adapter ring. Because K keeps the 45.46mm M42 register, M42 lenses also mount on K bodies with a thin adapter and keep infinity.
| Camera system | Adapter | Infinity focus | Frames like | Guide |
|---|---|---|---|---|
| Sony E | Plain mechanical, 27.46mm | Yes | 50mm on full frame; 75mm on APS-C (1.5x) | Pentax K to Sony E |
| Fuji X | Plain mechanical, 27.76mm | Yes | 75mm on APS-C (1.5x) | Pentax K to Fuji X |
| MFT | Plain mechanical, 26.21mm | Yes | 100mm on Four Thirds (2x) | Pentax K to MFT |
| Canon RF | Plain mechanical, 25.46mm | Yes | 50mm on full frame; 80mm on APS-C (1.6x) | Pentax K to Canon RF |
| Nikon Z | Plain mechanical, 29.46mm | Yes | 50mm on full frame; 75mm on APS-C (1.5x) | Pentax K to Nikon Z |
| L-mount | Plain mechanical, 25.46mm | Yes | 50mm on full frame; 75mm on APS-C (1.5x) | Pentax K to L-mount |
Frequently asked
What mount is the Pentax SMC Pentax-M 50mm f/1.4?
The Pentax SMC Pentax-M 50mm f/1.4 has a native Pentax K mount. Pentax K is the 1975 bayonet that replaced M42 while keeping its 45.46mm register, and it remains in use on Pentax DSLRs today. With a plain mechanical adapter it fits Sony E, Fuji X, MFT, Canon RF, Nikon Z, and L-mount bodies and keeps infinity focus.
How much is the Pentax SMC Pentax-M 50mm f/1.4 worth in 2026?
A used Pentax SMC Pentax-M 50mm f/1.4 typically sells for $60 to $210, with most clean working examples near $110. Basis: eBay sold listings and KEH, 2024-2025. This is an estimate, not an appraisal; condition, variant, and service history move the number.
Does the Pentax SMC Pentax-M 50mm f/1.4 work on Sony E, Fuji X, and MFT?
Yes. Pentax K has a 45.46mm register and every mirrorless mount is shorter (16mm to 20mm), so a simple Pentax K adapter reaches infinity with no optics. On a full-frame body the Pentax SMC Pentax-M 50mm f/1.4 frames as a 50mm lens; on APS-C (1.5x) it frames like a 75mm, on Canon APS-C (1.6x) like a 80mm, and on Micro Four Thirds (2x) like a 100mm. Plain adapter ring. Because K keeps the 45.46mm M42 register, M42 lenses also mount on K bodies with a thin adapter and keep infinity.
When was the Pentax SMC Pentax-M 50mm f/1.4 made?
Pentax made the SMC Pentax-M 50mm f/1.4 from 1977-1984. That puts the Pentax SMC Pentax-M 50mm f/1.4 2 years into the life of the Pentax K mount, which appeared in 1975 on the Pentax K2, KX, and KM.
What is the optical design of the Pentax SMC Pentax-M 50mm f/1.4?
The Pentax SMC Pentax-M 50mm f/1.4 uses 7 elements / 6 groups, Double Gauss. Double Gauss designs are near-symmetrical six- or seven-element formulas that support fast apertures with good correction; fast versions show glow from spherical aberration and swirl from mechanical vignetting wide open.
Which lenses are similar to the Pentax SMC Pentax-M 50mm f/1.4?
Close alternatives in the same focal class are the Nikon Nikkor-S Auto 50mm f/1.4 (pre-AI) (50mm f/1.4, $60 to $220), the Canon FD 50mm f/1.4 S.S.C. (50mm f/1.4, $55 to $200), and the Asahi Pentax Super-Multi-Coated Takumar 50mm f/1.4 (50mm f/1.4, $70 to $240). The Canon FD 50mm f/1.4 S.S.C. costs less on the used market.
Alternatives to the SMC Pentax-M 50mm f/1.4
Lenses within 15mm of 50mm from other makers, ranked by how close they sit in focal length, aperture, and price.
Side-by-side comparisons
- Pentax SMC Pentax-M 50mm f/1.4 vs Asahi Pentax Super-Multi-Coated Takumar 50mm f/1.4
- Pentax SMC Pentax-M 50mm f/1.4 vs Asahi Pentax Super-Takumar 50mm f/1.4
- Pentax SMC Pentax-M 50mm f/1.4 vs Canon FD 50mm f/1.4 S.S.C.
- Pentax SMC Pentax-M 50mm f/1.4 vs Carl Zeiss Planar T* 50mm f/1.4 (C/Y)
- Pentax SMC Pentax-M 50mm f/1.4 vs Minolta MD Rokkor 50mm f/1.4
- Pentax SMC Pentax-M 50mm f/1.4 vs Nikon Nikkor-S Auto 50mm f/1.4 (pre-AI)
- Pentax SMC Pentax-M 50mm f/1.4 vs Olympus OM-System Zuiko Auto-S 50mm f/1.4