Data sheet: Pentax-110 18 mm f/2.8

Pekka Buttler, 06/2023


The table below summarizes the lens’ key specifications (measurements are based on the pictured sample):

Brand:Asahi Opt.Co. (Pentax)Lens namePENTAX-110 1:2.8 18mm
Focal length(s)118 mmAngle-of-view262 °
Maximum Aperturef/2.8In Production1978–1985
Lens mountPentax 110Subfamily (if applicable)––
Length321 mmDiameter434 mm
Filter ring diameter30,5 mmWeight28 grams
Lens element count6Lens group count6
Aperture blades (S/R/C)5none (aperture in body)Focus throw130 °
Minimum focusing distance25 cmsMaximum magnification1:11,8
Has manual aperture ringNOHas Manual focus ringYES

Further notes:
• This lens was the widest lens for the Pentax-110 system.
• at 28 grams it is more than double the weight of the system’s standard lens, but is nevertheless a tiny lens.

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).

The Pentax 110 system

As so often happens with gadgets:
• First they are sold simply by being new…
• Then they are sold by adding nifty/attractive features
• Then they are sold by being smaller than earlier generations.
• …

In the mid 1970s, SLR cameras were on the verge of transitioning from the second stage to the third. The Olympus OM-1 (1975) was designed to be the most svelte full-featured SLR; the Pentax ME (1976) managed to be even smaller … suddenly miniaturisation was all the rage.

Around the mid 1970s Asahi/Pentax was offered the prototype of an interchangeable lens SLR using the 110-format film cassette, and they thought the opportunity was too good to pass up. In combination with Pentax’ lens design prowess the Pentax-110 system6 was introduced to the market in 1978.

Initially the system comprised of one body (the auto 110), an autowinder, a flash unit and three primes (18, 24 and 50 mm), in 1981 three more lenses (two primes and a zoom) were introduced and in 1982 the body was upgraded (to the auto 110 super). The entire Pentax-110 lineup was discontinued in 1985.

The entire Pentax-110 system was (as the name indicates) designed around the Kodak 110-format film cassette. This film cassette offered a 13 mm x 17 mm frame for exposure, meaning a 2,02 x crop factor (compared to 35 mm film). Hence, the original three lenses offered fields of view comparable to those of a 35 mm, a 50 mm and a 100 mm lens.

The Pentax-110 system was not without its quirks. Firstly, it might just be that the system was too tiny for many hands. The fact that the Pentax-110 system offered very little in the way of manual controls (auto exposure only) was in part predicated on that the body was so minute that manual controls would have been impractical. Also, given that the 110-format film was designed to offer a handy way to take quick snaps (on the expense of total resolution), the rest of the Pentax-110 system might just have been a bit of overkill. Finally, the Pentax auto 110 (super) bodies used a rectangular aperture mechanism that doubled as a shutter, meaning that the lenses lacked an aperture mechanism (and there was no lens-body communication).


This lens was only ever produced in one version.


If you want to natively mount this lens you need to find a functioning Pentax auto 110 (super) SLR camera. Luckily that is not entirely impossible. While it seems likely that Pentax was disappointed with Pentax-110 sales, the bodies did sell reasonably well, and many of them are still in circulation. Now that you can again get 110-format film, the remaining functioning cameras are however no longer sold for a pittance.

Due to the short flange focal distance used by the Pentax-110 mount (27 mm), adapting Pentax-110 lenses to a SLR/dSLR is practically impossible.

Adapting this lens to a mirrorless camera is possible, but has both some quirks and limitations. While practically all mirrorless cameras have a flange focal distance shorter than that of the Pentax-110 system, the Pentax-110 lenses are designed for a sufficiently smaller image circle. In terms of native-like field of view, micro Four Thirds mirrorless cameras offer an almost perfect match, but using Pentax-110 lenses on APS-C sensors (or larger sensors in APS-C crop mode) is not impossible (with the 18/2.8 there is moderate vignetting on APS-C sensors, but no hard vignetting). Finally, one must consider that as the Pentax-110 lenses lack an aperture mechanism of their own, you will likely be forced to either use the lens wide open or to jury-rig some form of aperture mask.


1 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’.

2 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

3 Length is given from the mount flange to the front of lens at infinity.

4 Diameter excludes protrusions such as rabbit ears or stop-down levers.

5 S=straight; R=rounded; C=(almost)circular at all apertures.

6 Officially, Pentax referred to the system as the Pentax System 10 but it seems that people rather used the Pentax-110 name.

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