Data sheet: Chinon Auto Zoom 35-70mm f/2.7–3.5 (Pentax K)

Pekka Buttler, 02/2025

Specifications

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

Brand:	Chinon	Lens name	Auto Zoom MC 35–70mm 1:2.7–3.5
Focal length range1	35–70 mm	Angle-of-view2	63.4–34.3 °
Maximum Aperture	f/2.7–3.5	In Production	1980s3
Lens mount	Pentax K	Subfamily (if applicable)	––
Length4	85,1 mm	Diameter5	65,3 mm
Filter ring diameter	58 mm	Weight	442 grams
Lens element count	7	Lens group count	7
Aperture blades (S/R/C)6	8 S	Focus throw	180 °
Minimum focusing distance (measured)	78 cm@35mm; 67 cm@70mm; 25 cm@macro mode	Maximum magnification (measured)	1:9,7 (@70 mm) 1:2,4 (macro mode)
Has manual aperture ring	YES	Has Manual focus ring	YES
Aperture mechanism type	Automatic	Aperture click stops7	2.7-4-5.6-8-11-16-22

Further notes:
• This standard zoom has rather ambitious specifications. While it does not offer a constant maximum aperture (a hallmark of a pro zoom lens), it does offer an exceptionally bright maximum aperture.
• It is a two-ring zoom with the front ring controlling focus and the rear ring controlling focal length (zoom).
• The lens changes shape considerably when zooming. The lens is at its longest at the 35 mm setting, and shortest at the 70 mm setting. The overall zoom extension is ≈20 millimetres.
• Furthermore the lens changes length when focusing and the focus extension is another ≈8 millimetres.
• The filter threads rotate when focusing.
• This lens offers a semi-decent minimum focusing distance for a legacy zoom lens. That the lens furthermore offers a macro mode which allows a maximum magnification of 1:2,4 makes this lens a strong contended for the title of ultimate all-rounder.

Versions and origins

There seems to be only one cosmetic version of the Chinon Auto Zoom MC 35-70mm f/2.7–3.5 lens. Boring.

However, in terms of origins it gets a bit interesting.

Chinon did not manufacture its own lenses (Chinon focused on camera manufacture), instead sourcing its lenses from various Japanese lens manufacturers, ranging from small manufacturers few have ever heard about to well-known (and -respected) companies such as Tomioka.

Often it is possible to – through the sleuthwork of comparing a Chinon lens to other lenses – deduce something about the likely manufacturers. However, in this case this is made difficult by that there are no other Japanese lenses that even share the same mainline specifications of a 35–70 zoom range in combination with the rather unusual maximum aperture of f/2.7–3.5.

There is however one contemporary lens that shares the exactly same mainline specifications and that’s the Carl Zeiss Jena Vario-Prakticar/Vario-Pancolar 35-70/2.7-3.5 [data sweet]. Moreover both lenses are outwardly somewhat similar and both lenses have a button-activated macro mode beyond the 70 mm setting. And Carl Zeiss Jena was known to sometimes license its designs to Japanese manufacturers. This has led to some speculation online that the lowly Chinon might in fact be a shortcut to a rather prestigious Carl Zeiss Jena design.

Owning both lenses I can unequivocally say that this Chinon is NOT a rebrand of the Carl Zeiss Jena Vario-Prakticar/Vario-Pancolar 35-70/2.7-3.5 (and a short article to that effect is forthcoming). However, I cannot entirely refute that some level of inspiration might have taken place (given the commonalities, I would think that whichever Japanese lens manufacturer designed this Chinon 35-70/2.7-3.5 probably drew more than a little inspiration from the Jena product).

Alas, unless one of my well-informed readers can effectively enlighten me, we will have to accept that the origin story of this Chinon lens will not be uncovered here.

Chinon company profile

Chinon is known to still photographers as one of the more advanced 2^nd 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

n.B! The following applies to all non-electronic Pentax K mount lenses.

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 natively on any Pentax dSLR.

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

1. 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’. ↩︎
2. 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 ↩︎
3. Documentation (e.g. brochures) of Chinon lenses are scarce and manuals are of no help in trying to date Chinon lenses as pictures in manuals surprisingly often show lenses that differ from those that were actually produced. Hence, dating these lenses is surprisingly difficult. ↩︎
4. Length is given from the mount flange to the front of lens at infinity. Measured unless stated otherwise. ↩︎
5. Diameter excludes protrusions such as rabbit ears or stop-down levers. Measured unless stated otherwise. ↩︎
6. S=straight; R=rounded; C=(almost)circular at all apertures. ↩︎
7. Numbers equal aperture values on aperture ring; • intermediate click; – no intermediate click. ↩︎