Pekka Buttler, 06/2025
Specifications
The table below summarizes the lens’ key specifications (measurements based on pictured sample):
| Brand: | Mamiya/Sekor | Lens name | Auto 1:2 f=50mm |
| Focal length(s)1 | 50 mm | Angle-of-view2 | 46,8 ° |
| Maximum Aperture | f/2 | In Production | 1966-1971 |
| Lens mount | M42 | Subfamily (if applicable) | –– |
| Length3 | 38,9 mm | Diameter4 | 60,2 mm |
| Filter ring diameter | 52 mm | Weight | 212 grams |
| Lens element count | 6 | Lens group count | 4 |
| Aperture blades (S/R/C)5 | 6 S | Focus throw | 260 ° |
| Minimum focusing distance (measured) | 49 cms | Maximum magnification (measured) | 1:7,6 |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
| Aperture mechanism type | Automatic (with auto/manual switch) | Aperture click stops6 | 2•2.8•4•5.6•8•11-16 |
Further notes:
• In 1966 Mamiya introduced the TL line (TL500 and TL1000) of cameras and lenses. The TL line supported through-the-lens metering (in stop-down mode). That line was extended in 1968 to the DTL line (500DTL and 1000DTL followed in 1969 by the 2000DTL) that offered the choice between spot and area metering
• These cameras were vanilla auto aperture M42 cameras, meaning that they did not rely on any special or proprietary features in either cameras or lenses. See more in the article on all Mamiya 35 mm lens mounts.
• Mamiya’s lineup of M42 lenses was relatively comprehensive, although it seems that some of these lenses were closely related to a number of Tokina lenses.
• As part of that lineup were four standard lenses:
• Auto Mamiya/Sekor 55 mm f/1.4
• Auto Mamiya/Sekor 55 mm f/1.8
• Auto Mamiya/Sekor 50 mm f/2 [this lens]
• Auto Mamiya/Sekor 50 mm f/2.8
Versions and related lenses
Within the relatively short timespan of the Mamiya M42/TL system, two cosmetically different but optically similar versions of the Auto Mamiya/Sekor 50 mm f/2 were manufactured.
The earlier version followed a two-colour (black and silver) scheme whereas the later (pictured) version was all-black.
While this was the first time Mamiya offered a 50 mm f/2 lens, it was not the last. Also the Mamiya M42/SX lineup (1974–1978) and the Mamiya Z/E lineup (1980–1984) sported a 50 mm f/2 design and in all cases the fundamental approach (6 elements in 4 groups) was the same. However, close inspection of the lens schematics of these three generations of Mamiya 50 mm f/2 lenses indicate that each generation was subtly different.
History of Mamiya M42 lenses
Please see the JAPB article on all (7) Mamiya SLR lens mounts to understand the role of the Mamiya M42(standard) mount .
Adapting
n.B! The following applies to all Mamiya M42 (non-SX) mount lenses.
This lens cannot be used natively on any current SLR or dSLRs. To use it in its native environment, you will need a standard M42 mount film camera by Mamiya or any other manufacturer. While the Mamiya standard M42 system was not especially long-lasting, the cameras and lenses were thoughtfully designed and well-made and many remain perfectly serviceable today.
Should you aim to adapt this lens to a mirrorless camera you will need an M42 adapter. The popularity of the M42 mount means that special adapters (helicoid adapters, tilt/shift adapter and speed boosters) are relatively readily available.
Using M42 lenses on dSLRs can also an easy option, assuming you can find an adapter. Thereafter your level of success in adapting also depends on which dSLR you are hoping to adapt to:
• Canon EF, Minolta / Sony A and Pentax K dSLRs are able to mount M42 lenses perfectly using a simple adapter ring.
• Nikon F dSLRs have a long flange focal distance, meaning that mounting M42 lenses needs an adapter that uses corrective optics to allow anything close to infinity focus.
Footnotes
- 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’. ↩︎
- 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 ↩︎ - Length is given from the mount flange to the front of lens at infinity. ↩︎
- Diameter excludes protrusions such as rabbit ears or stop-down levers. ↩︎
- S=straight; R=rounded; C=(almost)circular at all apertures. ↩︎
- Numbers equal aperture values on aperture ring;• intermediate click; – no intermediate click ↩︎