Quick answer
The Pentax smc Pentax-M 20mm f/4 is a ultra-wide prime lens covering 20mm at f/4.0 for the Pentax K mount. Its moderate maximum aperture works best in good light or with a higher ISO.
About this lens
Pentax smc Pentax-M 20mm f/4: a wide-angle prime lens with a 20mm focal length and a maximum aperture of f/4, made for Pentax K mount cameras. The wide view suits landscapes, architecture and environmental shots.
Pentax smc Pentax-M 20mm f/4 specifications
What can you shoot with the Pentax smc Pentax-M 20mm f/4?
At 20mm this is a ultra-wide prime, which typically suits:
- Landscapes and big skies
- Architecture and interiors
- Astrophotography and night skies
Its moderate maximum aperture works best in good light or with a higher ISO.
Full-frame equivalent and field of view
Calculated from the focal length and crop factor. Not measured.
| Sensor | Crop | Equivalent | Horizontal FOV | Diagonal FOV |
|---|---|---|---|---|
| Full frame | 1.0x | 20mm | 84° | 94.5° |
| APS-C | 1.5x | 30mm | 61.9° | 71.6° |
Frequently asked questions
What mount does the Pentax smc Pentax-M 20mm f/4 use?
It uses the Pentax K mount, so it fits Pentax K cameras directly.
What is the focal length of the Pentax smc Pentax-M 20mm f/4?
It is a fixed 20mm lens with a maximum aperture of f/4.0. That makes it a ultra-wide lens.
Is the Pentax smc Pentax-M 20mm f/4 a prime or a zoom lens?
It is a prime lens with a fixed 20mm focal length. Primes usually open wider than zooms; this one opens to f/4.0.
What is the Pentax smc Pentax-M 20mm f/4 equivalent on a crop sensor?
On APS-C (1.5x crop) it frames like 30mm on full frame, with a 61.9° horizontal and 71.6° diagonal field of view. These figures are calculated from the focal length and crop factor.
Which cameras does the Pentax smc Pentax-M 20mm f/4 fit?
Any Pentax K-mount camera, including Pentax K-1, Pentax K-3, Pentax K-3 II, Pentax K-3 Mark III, and Pentax K-30 and 15 more.
Alternatives for Pentax K from other brands
All Pentax K lensesSame mount, overlapping focal range, closest maximum aperture first.
