Pekka Buttler, 08/2022
Specifications
The table below summarizes the lens’ key specifications:
| Brand: | Porst | Lens name | Color Reflex 1:1.2/50 mm UMC X-M G |
| Focal length(s)1 | 50 mm | Angle-of-view2 | 45°22′ |
| Maximum Aperture | f/1.2 | In Production | ≈1980–1985 |
| Lens mount | Fujica X | Subfamily (if applicable) | –– |
| Length3 | 50,4 mm | Diameter4 | 65,6 mm |
| Filter ring diameter | 55 mm | Weight | 299 grams |
| Lens element count | 7 | Lens group count | 7 |
| Aperture blades (S/R/C)5 | 6 S | Focus throw | ≈185 ° |
| Minimum focusing distance | 45 cm | Maximum magnification | 1:6,7 |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
Further notes:
• Firstly, this lens is a 1:1 rebrand of the EBC X-Fujinon 50 mm f/1.2 lens. If you have the lenses side by side, you’ll notice that the only change is in the lens’ name ring.
• While the lens name ring uses Porst nomenclature (UMC) this lens sports Fuji’s proprietary coating technology referred to as ‘Electron Beam Coating’ or – in short – EBC.
• The ‘X-M’ in the lens’ name stands for DM (in Fuji terms), or “Dial Mode” and means that the lens can be used (on a Fujica X or Porst body) in program and shutter priority mode, once the aperture ring’s auto setting is engaged.
• Besides aperture ring and focus ring, this lens has a button to control the aperture ring’s auto setting (indicated by the yellow diamond). To enter or exit the auto setting, that button has to be pressed.
History
See the JAPB company profile on Porst for more information about the company.
Porst sourced its lenses widely. While some of Porst lenses – as here is the case – were direct rebrands of identical lenses of major brands, most were sourced from (mostly Japanese) off-brand/OEM manufacturers. This lens originates from the fruitful co-operation between Porst and Fuji Photo Film in the 1980s.
Fuji Photo Film (nowadays: Fujifilm) was among the last major manufacturers to abandon the m42 thread mount for a proprietary lens mount. The Fujica STX-1 camera (introduced 1979) introduced a new lens mount (typically referred to as the Fujica X mount, not to be mistaken for the modern Fujifilm X mount) and a series of new lenses.
While many (if not most) of the lenses initially introduced for the Fujica X -mount were simply old (and venerable) Fuji Photo Film designs from the m42 lens crammed into a new housing with a new mount, Fuji Photo Film also embarked on an ambitious but short-lived endeavour to modernise its lens lineup. This lens represents the high-end of Fuji’s redesigned series of standard primes composed of the 50 mm f/1.9 (a nifty fifty), the 50 mm f/1.6 (a faster fifty), and this: the 50 mm f/1.2 (a super fast fifty).
Fuji has long been known for its high quality lenses – both in SLR’s compacts and medium and large format lenses – and it would have been interesting to see what Fuji Photo Film’s lineup of Fujica X lenses would have developed into. Alas, in the mid-1980s, Fuji Photo Film decided to withdraw from SLR manufacture and focused instead on both compacts and larger film formats. Whether that withdrawal was caused by disappointing sales of the Fujica X line, or due to the advent of autofocus SLR’s, I can only speculate.
Adapting
The only cameras able to natively mount Fujica X lenses are the Fujica STX and AX lines of manual focus, film SLRs and its rebrands (such as the Porst CR-line of SLR’s). Should you want to use this lens on film, you can count yourself lucky that the AX and STX lines of Fujica’s (and Porst CR’s) generally seem to have well designed and manufactured, hence making compatible film bodies readily available for a pittance.
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). However, due to the method of aperture control used the Fujica X lenses, the adapter will need a control ring to allow stopping down the lens (and you will need to remember to engage that ring). However, thanks to the relative scarcity of Fujica X lenses (caused, in part, by the shortish production run), Fujica X adapters are not quite as readily available as for more common, film-era mounts. Hence, while regular adapters are not difficult to come by, specialised adapters (such as speed boosters or tilt/shift adapters) are not easy to obtain.
Due to the shortish flange focal distance used by the Fujica X mount (43,5 mm), adapting this lens to dSLR/SLR mounts is not as problem-free, and – to retain anything near infinity focus – the adapter will necessitate corrective optics. Even so, adapters to many dSLR mounts are available.
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.