Quick answer
The Pentax smc Pentax-K 21mm f/3.5 is a ultra-wide prime lens covering 21mm at f/3.5 for the Pentax K mount. Its moderate maximum aperture works best in good light or with a higher ISO.
About this lens
This 21mm f/3.5 wide-angle prime lens from Pentax fits Pentax K mount cameras. The wide view suits landscapes, architecture and environmental shots.
Pentax smc Pentax-K 21mm f/3.5 specifications
What can you shoot with the Pentax smc Pentax-K 21mm f/3.5?
At 21mm 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 | 21mm | 81.2° | 91.7° |
| APS-C | 1.5x | 32mm | 59.5° | 69° |
Frequently asked questions
What mount does the Pentax smc Pentax-K 21mm f/3.5 use?
It uses the Pentax K mount, so it fits Pentax K cameras directly.
What is the focal length of the Pentax smc Pentax-K 21mm f/3.5?
It is a fixed 21mm lens with a maximum aperture of f/3.5. That makes it a ultra-wide lens.
Is the Pentax smc Pentax-K 21mm f/3.5 a prime or a zoom lens?
It is a prime lens with a fixed 21mm focal length. Primes usually open wider than zooms; this one opens to f/3.5.
What is the Pentax smc Pentax-K 21mm f/3.5 equivalent on a crop sensor?
On APS-C (1.5x crop) it frames like 32mm on full frame, with a 59.5° horizontal and 69° diagonal field of view. These figures are calculated from the focal length and crop factor.
Which cameras does the Pentax smc Pentax-K 21mm f/3.5 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.
