Pekka Buttler, 10/2026
Specifications
The table below summarises the lens’ key specifications (measurements based on pictured sample):
| Brand: | Chinon (Chinonflex) | Lens name | Auto Reflex 1:2.8 f=100mm |
| Focal length(s)1 | 100 mm | Angle-of-view2 | 24° |
| Maximum Aperture | f/2.8 | In Production | likely |
| Lens mount (this lens) | Minolta SR | Other lens mounts | Canon FL, M42, Nikon F |
| Length3 | 58,5 mm | Diameter4 | 60,3 mm |
| Filter ring diameter | 52 mm | Weight | 354 grams |
| Lens element count | unknown | Lens group count | unknown |
| Aperture blades (S/R/C)5 | 6 S | Focus throw | ≈280 ° |
| Minimum focusing distance (measured) | 118 cm | Maximum magnification (measured) | 1:9,7 |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
| Aperture mechanism type | Automatic with manual stop-down | Aperture click stops6 | 2.8-4•5.6•8•11•16•22 |
Further notes:
• I have not been able to find a description of the optical recipe (elements and groups) for the pictured lens.
• When offered in Minolta SR mount (such as with this lens), the base of the lens offers a lever to facilitate depth-of-field preview
Historical notes:
• Chinon entered SLR manufacture relatively late (around 1968), and as a first step Chinon sold a camera named Chinonflex, along with a set of primes ranging from 28 to 200 mm, baring the same ‘Chinonflex’ name.
• While Chinon in later years focused on offering lenses only with those mounts that Chinon was also using on its cameras (initially M42 and later Pentax K), in this early phase, ‘Chinonflex’ lenses were offered also for some other major lens mounts. While I have not been able to find a brochure or definitive list, I’ve seen ‘Chinonflex’ lenses for Canon FL, M42, Minolta SR and Nikon F mounts.
Versions and origins
Chinon did not manufacture its own lenses (Chinon focused on camera manufacture), instead sourcing its lenses from various Japanese lens manufacturers, including Tomioka.
There are at least two different 100 mm f/2.8 lenses sold by Chinon:
The first version is the pictured ‘Chinonflex auto reflex’ lens, that was available in several different mounts. This same lens was also sold by some rebranders (I’ve definitely seen it as a ‘Porst’ (see company profile)). Which Japanese company is to be thanked for the manufacture of this lens is unclear.
The second version was sold under the ‘Auto Chinon’ name, with some samples also proudly sporting the name ‘Tomioka’ on the lens’ name ring (“Auto Chinon 1:2.8/100 Tomioka Japan”). Whether that means that some samples were manufactured by Tomioka and other samples (of an outwardly identical lens) were not is unclear.
Chinon company profile
Chinon is known to still photographers as one of the more advanced 2nd tier Japanese cameramakers. From 1971 to the late 1980s Chinon was known to enthusiast photographers the world over for combining technological advancements in cost-effective cameras bodies. See more details in the Chinon company profile.
Adapting
This lens cannot be used natively on any current SLR or dSLRs. To use it in its native environment, you will need a Minolta SR (SR/MC/MD/X-600) film camera. Luckily these are quite easy to find.
Thanks to being a fully manual lens (manual aperture, manual focus), the lens can be adapted to all mirrorless cameras using a suitable adapter. Moreover, a simple ‘dumb adapter’ will do the job perfectly. Thanks to the popularity of the Minolta SR mount, the availability of adapters to all mirrorless mounts can be taken for granted, on the other hand, specialist adapters (speed boosters, helicoid adapters, tilt/shift adapters) are not available for all mirrorless mounts, but daisy-chaining adapters (e.g. Minolta SR -> Canon EF; Canon EF –> mirrorless) can offer a work-around.
Using Minolta SR mount lenses on dSLRs is also be an option, but it is not trouble-free due to that the Minolta SR mount’s flange focal distance is shorter than that of any dSLR mount (technically with the exception of Olympus’ four thirds mount). Hence, any attempt at adapting Minolta SR lenses must rely on an adapter that uses corrective optics to allow infinity focus. However, such adapters are readily available.
Footnotes
- Focal length is (unless stated otherwise) given in absolute terms (not in Full-frame equivalent), and according to the manufacturer’s naming practice (which does not always reflect the lens’ actual field of view). For an understanding of whether the lens is wide/tele, see ‘Angle-of-view’. ↩︎
- Picture angle is given in degrees 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. Measured unless stated otherwise. ↩︎
- Diameter excludes protrusions such as rabbit ears or stop-down levers. Measured unless stated otherwise. ↩︎
- S=straight; R=rounded; C=(almost)circular at all apertures. ↩︎
- Numbers equal aperture values on aperture ring; • intermediate click; – no intermediate click. ↩︎