Pekka Buttler, 10/2024
Specifications
The table below summarizes the lens’ key specifications (measurements based on pictured sample):
| Brand: | Mamiya/Sekor | Lens name | SX 1:1.8 f=55mm |
| Focal length(s)1 | 55 mm | Angle-of-view2 | 42,9° |
| Maximum Aperture | f/1.8 | In Production | 1974-1977 |
| Lens mount | Mamiya M42/SX | Subfamily (if applicable) | –– |
| Length3 | 39,0 mm | Diameter4 | 62,3 mm |
| Filter ring diameter | 52 mm | Weight | 183 grams |
| Lens element count | 6 | Lens group count | 5 |
| Aperture blades (S/R/C)5 | 6 S | Focus throw | 290 ° |
| Minimum focusing distance | 45 cms | Maximum magnification | 1:6,0 |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
| Aperture mechanism type | Auto | Aperture click stops6 | 1.8••2.8•4•5.6•8•11-16 |
Further notes:
• In May 1974 Mamiya introduced the MSX line (MSX500 and MSX1000) of cameras and lenses. The MSX line was quickly followed by the DSX7 line (DSX500 and DSX1000) of cameras.
• The MSX/DSX line of cameras could use the entire repertoire of M42 lenses (including Mamiya’s previous M42 lenses), but these cameras really came into their own when used with Mamiya M42/SX lenses. These lenses not only enabled locking lenses on the camera body, but communicated the selected aperture to the camera by means of a pin in the base of the aperture ring (see below). This pin – incidentally – made Mamiya M42 SX lenses incompatible with most M42 camera bodies.
• Mamiya’s lineup of M42/SX lenses was relatively comprehensive, ranging from a 14 mm fisheye to a 800mm ultra-tele lens.
• As part of that lineup were three standard lenses:
• Auto Mamiya/Sekor SX 55 mm f/1.4
• Auto Mamiya/Sekor SX 55 mm f/1.8 [this lens]
• Auto Mamiya/Sekor SX 50 mm f/2
Versions and related lenses
Within the relatively short timespan of the Mamiya M42 SX system, I am not aware of more than one variant of the SX 55 mm f/1.8 lens having been manufactured.
The Auto Mamiya/Sekor SX 55 mm f/1.8 lens is the successor of the Mamiya/Sekor ES 55 mm f/1.8 lens and it seems to have inherited the same optical design.
On the other hand, the Auto Mamiya/Sekor SX 55 mm f/1.8 is optically clearly different from the very similarly named Auto Mamiya/Sekor 55/1.8, which was a 6 elements in 4 groups design).
The Auto Mamiya/Sekor SX 55 mm f/1.8 lens is also the last 55 mm nifty fifty that Mamiya designed as the subsequent NC/CS line of cameras and lenses was redesigned to use 50 mm as the standard focal length.
History of Mamiya M42/SX lenses
Please see the JAPB article on all (7) Mamiya SLR lens mounts to understand the role of the Mamiya M42/SX mount .
Adapting
n.B! The following applies to all Mamiya M42/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 Mamiya MSX or DSX-series film body. While the Mamiya MSX/DSX system was quickly overtaken by events, the cameras themselves 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 that does not conflict with the aperture ring linkage pin (in the base of the aperture ring). Luckily, most M42 adapters I’ve seen does allow mounting Mamiya M42/SX lenses. 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, but you will (again) have to find an adapter that does give room for the aperture ring linkage pin. 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 ↩︎
- While the MSX line offers typical TTL spot metering, the DSX offers dual metering systems, allowing the user to choose between spot metering and average metering – something Mamiya had first introduced in 1968 with the DTL line of cameras.. ↩︎