Data sheet: Kenlock 135 mm f/2.8 (Nikon F)

Pekka Buttler, 03/2026

Specifications

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

Brand:	Kenlock	Lens name	f=135 mm 1:2.8 AUTO
Focal length 1	135 mm	Angle-of-view 2	≈18°
Maximum Aperture	f/2.8	In Production	≈1960s–70s
Lens mount	Nikon F	Subfamily (if applicable)	Pre-Ai (Ai’d)
Length 3	74,6 mm	Diameter 4	66,8 mm
Filter ring diameter	58 mm	Weight	373 grams
Lens element count	?	Lens group count	? (see below)
Aperture blades (S/R/C) 5	6 S	Focus throw	≈90 °
Minimum focusing distance (measured)	183 cms	Maximum magnification (measured)	1:10,6
Has manual aperture ring	YES	Has Manual focus ring	YES
Aperture mechanism type	Automatic	Aperture click stops 6	12.8-4-5.6-8-11-16-22

Further notes:
• This lens is just one of countless legacy era 135 mm f/2.8 lenses
• While I have not found documentation detailing the lens’ optical recipe, it is highly likely that it – like most 1970s third party 135/2.8 lenses – uses a 4 elements in 4 groups design derived from the original Ernostar design.
• This lens was manufactured by Mitake Optical and was – throughout the years – sold under many rebrands, including Formula 5, Kamero, Owen, Pentor, Revuenon, Samigon. As such, it was available in a wide range of period-relevant lens mounts.

Versions

This is not the only “Kenlock 135 mm f/2.8” lens.
First, there is a slightly newer version that is multicoated but otherwise similar.
Second, there is a multicoated version sporting a 55 mm thread and the “Kenlock MC•tor” name
Third, there is a Kenlock 135/2.8 lens that also includes a macro mode and uses a 52 mm thread.
Fourth, there is a version that sports multicoating and a 52 mm filter thread, but no macro mode.

Also, it seems that there is a 135 mm f/2.8 Kenlock lens that uses a preset aperture.

Adapting

There are good chances this lens can still be used natively:
• If the lens has been AI’d, this lens can be used natively on all current high-end Nikon dSLRs and several earlier medium-to-high-end older Nikon dSLRs ⁷ as well as all post-1977 Nikon Film cameras.
• If it is in its original Pre-Ai form, it can be used natively on the Nikon Df and on all Nikon F-mount film cameras produced before 1977.

Thanks to being a fully manual lens (manual aperture, manual focus), the lens can be adapted to all mirrorless cameras using a suitable dumb adapter (and such adapters are easy to find). Moreover, a large range of special adapters (helicoid adapters, tilt/shift adapters, speed boosters) for using Nikon F lenses on most mirrorless systems are available.

Using Nikon F lenses on non-Nikon SLRs and dSLRs is likewise a distinct possibility. Thanks to the relatively generous flange focal distance of the Nikon F mount (46,5 mm), adapter rings for all dSLR mounts are available as well as for a goodly portion of film-era SLR mounts. Such rings may not allow for auto aperture, but even then the lenses can be used in stop-down metering mode.

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. Length is given from the mount flange to the front of lens at infinity. Measured unless stated otherwise. ↩︎
4. Diameter excludes protrusions such as rabbit ears or stop-down levers. Measured unless stated otherwise. ↩︎
5. S=straight; R=rounded; C=(almost)circular at all apertures. ↩︎
6. Numbers equal aperture values on aperture ring; • intermediate click; – no intermediate click. ↩︎
7. As of this writing, the following Nikon dSLRs fully support Aperture priority and manual metered modes on Nikkor Ai lenses: D2, D3, D4, D5, D6, D200, D300, D300s, D500, D600, D610, D700, D750, D780, D800, D800E, D810, D850, D7000, D7100, D7200 ↩︎