Pentax-110 Subminiature Lenses for Micro4/3



Pentax has a long history of making excellent optics of all kinds from eye glass lenses to medical endoscope and microscopes. Photographers know their SLR lenses which are often hailed as budget lenses with excellent color rendition and resolution. Founded in 1919 as Asahi Kogaku Goshi Kaisha in Tokyo Japan, the company saw success in various markets before later renamed itself to Asahi Optical Co., Ltd. The company made a distribution deal with Honeywell corporation which named the cameras and lenses Honeywell Pentax and then dropping the Honeywell name later. Finally the company was sold to Hoya corporation in 2007 and remains one of the larger optical manufacturing companies in the world despite their small market share today in photography. 

Pentax reached its height of popularity in the 1970’s and 1980’s with its K-mount manual iris lenses and later A-Mount auto iris lenses. Many of these lenses featured the legendary SMC Super Multi Coating which give the images a pleasing color and flare. Pentax lenses remain one of the best values due to their low cost and quality. Pentax had many lenses for various film formats developed over the years including 35mm, 645, and 6x7. The smallest format cameras developed were for the ill-fated 110 film system which was developed by film and camera manufacturers as an answer to demand for smaller cameras.

Pentax joined the 110 film camera party in 1978 with the Pentax 110 camera that featured three interchangeable lenses; the 18mm f/2.8, 24mm f/2.8, and 50mm f/2.8. In 1981 the company followed up with the 18mm Pan fixed focus (PF) lens, the 70mm f/2.8 and the 20-40mm f/2.8 Zoom. The 18mm PF lens and the Soligor 1.7x Tele Converter for the 110 system are fairly rare. The 1.7x converts the 50mm to a 119mm telephoto lens.


The Pentax 110 camera featured no user adjustments for iris or shutter. The focal plane shutter was inside the camera as was a rather square looking iris. The lenses contain no iris aperture control and only a manual helicoid focus mechanism with a very short focus throw going from infinity to close focus with a slight twist.

The 110 film negative measured 13mm x 17mm which was nearly half the size of 135 or 35mm film measuring at 24mm x 36mm which we know as “Full Frame” in today’s digital sensors. The small size enabled so called miniature or subminiature cameras which remained popular until the early 1980’s. 110 film is very similar to the modern Micro4/3 sensor size which is 10mm x 17.8mm. Some of the focal lengths have a larger image circle than Micro4/3 and can be adapted to Super35/APS-C sensor mirrorless cameras such as the Sony NEX system. Since there were no other 110 interchangeable lenses made, the Pentax 110 are the only lenses from this era and film format that can be adapted to modern mirrorless digital cameras. Due to the shallow flange depth of these lenses, they cannot be adapted to longer traditional SLR mounts like Canon EF or Nikon F.

The equivalents to 35mm film field of view are roughly 2x of the focal length for Micro4/3 and 1.6x the focal length for mirrorless APS-C cameras like Sony NEX. Therefore, the 18mm f/2.8 on a Micro4/3 camera is equivalent to a 36mm lens on a 35mm Full Frame camera (FF35). The 24mm is equivalent to approximately 50mm on FF35. The 50mm is equivalent to 100mm. The 70mm is equivalent to 140mm. Finally the 20-40mm on a Micro4/3 is equivalent field of view to a 40mm to 80mm on FF35.



Regarding size, the 24mm lens is the smallest in the bunch and about the diameter size of a US 25 Cent Quarter or a 1 Euro coin. The 18mm and 50mm are slightly larger than the 24mm fitting a similar form factor since they were all launched at the same time. The 70mm f/2.8 or 20-40mm f/2.8 are the largest in the series as they are more closely sized to a compact 50mm lens you would find in a standard 35mm SLR.

The lenses have similar ergonomics from one focal length to another however the 20-40mm is fairly unique with a push-pull zoom mechanism that is opposite most lenses of a similar design. The 20-40mm is most compact at 40mm and you push it longer to reach 20mm.

A series of UV and Close-Up Diopter filters were made for the lenses All the lenses have different size filter thread sizes including 25.5mm, 30.5mm, 37.5mm and the exception 70mm f/2.8 and 20-40mm f/2.8 with a matching 49mm filter thread. Below is a chart and original catalog pages with all the info on the lenses.


Focal Length


Angle of View

Minimum Focus Distance

Lens Dimensions

Filter Size


35mm Full Frame Equiv on MFT

18mm f/2.8


61.5 deg

0.25 meter





24mm f/2.8


47 deg

0.35 meter





50mm f/2.8


24 deg

0.9 meter





70mm f/2.8


17.2 deg

1.5 meter





20-40mm f/2.8


57.5 deg to 31 deg

0.7 meter







Here we have mounted a Pentax 110 system 24mm f/2.8 on an Olympus OM-D series Micro4/3 camera with a simple no iris control 110 to M43 adapter from Fotasy. As you can see, it is indeed subminiature and definitely a conversation piece if nothing else.  The images with this adapter allow the lens to have light enter uncontrolled and therefore are slightly lower contrast.

We were also able to find a 110-M43 Adapter in China from RJ Camera that has an iris built into it for improved bokeh and image control. All of the sample images here were shot with this adapter on the 110 lenses and intended only as reference and not a formal test. As you can see the lenses create a pleasing swirling bokeh with excellent color and resolution. Pentax claimed in their early marketing that these lenses could create images that could be enlarged to 8x10” or 11x14” prints.


The Pentax 110 system was popular enough that you can easily find these lenses for about $10 to $40 USD depending on condition and quality. Adapters can be bought from $17 for the Fotasy adapter or $75 for the RJ Camera iris control version.

As of the writing of this article, author Ryan Avery is offering the kit of all 5 lenses including the 18mm, 24mm, 50mm, 70mm, and 20-40mm along with the original camera, Fotasy adapter, and RJ Camera Iris adapter on


--Ryan Avery is Co-Founder at A life long photography and motion picture enthusiast, Ryan has traded used cameras and lenses of all kinds for decades as well as founding the Veydra lens brand and consulting for many of the world's top motion picture and photography optics brands.