Pekka Buttler, 01/2026
This lens was kindly provided for cataloguing by Vladimir at #photogears
Specifications
The table below summarizes the lens’ key specifications (measurements are based on the pictured sample):
| Brand: | Asahi Opt.Co. (Pentax) | Lens name | smc Pentax 1:2.8 24mm |
| Focal length(s) 1 | 24 mm | Angle-of-view 2 | 84 ° |
| Maximum Aperture | f/2.8 | In Production | 1977–1984 |
| Lens mounts | Pentax K | Subfamily (if applicable) | K |
| Length 3 | 42,7 mm | Diameter 4 | 62,9 mm |
| Filter ring diameter | 52 mm | Weight | 201 grams |
| Lens element count | 9 | Lens group count | 8 |
| Aperture blades (S/R/C) 5 | 5 S | Focus throw | unknown |
| Minimum focusing distance (indicated) | 25 cm | Maximum magnification (calculated) | 1:8.3 |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
| Aperture mechanism type | Automatic | Aperture click stops 6 | 2.8-4•5.6•8•11•16-22 |
Further notes:
• When Pentax introduced the new bayonet mount (and three cameras and more than two dozen lenses) in 1975, they initially introduced a 24 mm lens with a maximum aperture of f/3.5. That lens was a direct descendant of the 1967 Super-Takumar 24/3.5.
• Two years later, in 1977, Pentax introduced a faster version of the 24 mm prime, this 24/2.8. Not only was it faster, it was also smaller and lighter than the 24/3.5.
• The 24/2.8 introduced 1977 would stay in production until 1984 when it was succeeded by the KA-type smc Pentax-A 24 mm f/2.8.
• The recommended lens hood for this lens is the Pentax PH-S52 , but any 52 mm thread wide-angle hood will likely work just as well.
Versions
To the best of JAPB knowledge, only one variant of the smc Pentax 24 mm f/2.8 was ever made.
History of Asahi / Pentax
The camera business today known Pentax was founded in 1919 as Asahi Kogaku Kogyo (Asahi Optical Company). Initially the company manufactured lenses for eyeglasses, later diversifying into projection lenses and even later into photographic lenses, supplying lenses for camera makers such as Konishiroku (Konica) and Molta (Minolta) and binoculars.
In 1952 – the year of the Helsinki olympiad – Asahi released the Asahiflex, the first Japanese 35 mm SLR. Together with its SLR cameras, Asahi introduced a line of lenses that carried the name ‘Takumar’, in honour of the founder’s brother.
In 1975 Asahi/Pentax introduced its own bayonet mount – The Pentax K mount – and phased out the production of m42 lenses and cameras. The name Takumar would remain on Pentax lenses until 1979 (and made some sporadic reappearances). The Pentax K mount is still a current mount, but it has several versions/generations. For details, see the JAPB article on the Pentax K mount.
Pentax was among the handful of Japanese camera manufacturers to keep up with the introduction of autofocus SLR cameras, and even survived the shift from film SLRs to digital SLRs (albeit somewhat struggling).
Adapting
If you want to natively mount this lens you need to find a functioning Pentax K mount SLR (or a dSLR) camera. Luckily that should be relatively easy as Pentax K film bodies were produced in their millions and most of them – especially those manufactured by Pentax – have a good reliability record. Alternatively, you can use this lens on most high-end Pentax dSLRs, but only in stop-down metering mode.
Adapting this lens to a mirrorless, full-frame digital camera is a breeze thanks to the lens having full manual controls (aperture ring, focus ring). You simply need a dumb adapter from Pentax K to your mirrorless system.
Due to the medium flange focal distance used by the m42 mount (45,46 mm), whether you can adapt this lens to other than Pentax’ dSLR mounts depends on which dSLR mount: Canon EF, and Four Thirds can mount Pentax K lenses using a simple adapter ring. Minolta/Sony A and Nikon F on the other hand are not as problem-free, and – to retain anything near infinity focus – the adapter will necessitate corrective optics. In all cases, your camera will work only in stop-down metering.
Footnotes
- Focal length is (unless stated otherwise) given in absolute terms, and not in Full-frame equivalent. For an understanding of whether the lens is wide/tele, see ‘Angle-of-view’. ↩︎
- Picture angle is given in degrees (based on manufacturers’ specs) and concerns the diagonal picture angle. Rule of thumb:
> 90 ° ==> Ultra-wide-angle
70–90 ° ==> Wide-angle
50–70 ° ==> Moderate wide-angle
40–50 ° ==> ‘Standard’ or ‘normal’ lens
20–40 ° ==> Short tele lens
10-20 ° ==> Tele lens
5-10 ° ==> Long tele lens
< 5 ° ==> Ultra-tele lens ↩︎ - Length is given from the mount flange to the front of lens at infinity. ↩︎
- Diameter excludes protrusions such as rabbit ears or stop-down levers. ↩︎
- S=straight; R=rounded; C=(almost)circular at all apertures. ↩︎
- Numbers equal aperture values on aperture ring; • intermediate click; – no intermediate click. ↩︎