Pekka Buttler, 01/2023
Specifications
The table below summarizes the lens’ key specifications (Measurements based on pictured sample):
| Brand: | Minolta | Lens name | MC W.Rokkor-SG 1:3.5 f=28mm |
| Focal length(s)1 | 28 mm | Angle-of-view2 | 75,4 ° |
| Maximum Aperture | f/3.5 | In Production | 1966–1968 |
| Lens mounts | Minolta SR | Subfamily (if applicable) | MC (I) |
| Length3 | 50,5 mm | Diameter4 | 70,0 mm |
| Filter ring diameter | 67 mm | Weight | 307 grams |
| Lens element count | 7 | Lens group count | 7 |
| Aperture blades (S/R/C)5 | 6 S | Focus throw | 100 ° |
| Minimum focusing distance | 60 cms | Maximum magnification | 1:19,4 |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
Further notes:
• When Minolta introduced the Auto W.Rokkor- SG 28 mm f/3.5 (this lens’ direct predecessor) lens in 1963, it was the widest-angle regular lens for the Minolta SR (the preceding 21 mm lenses invade the mirror box and necessitate mirror lock-up and a separate viewfinder). The Minolta user base would have to wait until 1971 for a wider regular lens (the non-invasive 21 mm f/2.8) to be introduced.
• There are two MC I variants of the Minolta 28 mm f/3.5. This (1966–1968) version sporting a 67 mm filter ring diameter, and a later (1968–1970) version sporting the regular 55 mm filter ring diameter.
• The original Minolta D70KA 70 mm lens hood is a rectangular, clamp-on model, that commands a specialty item price. Problematically, generic 67 mm thread wide-angle lens hoods are not exactly common.
Versions
The ‘slow’ (f/3.5) 28 mm lens was present in the Minolta lens lineup from 1963 until the end of the Minolta SR system. During that time, it went through several iterations, and while many of these mostly reflected cosmetic and lens-body interface changes, the optical recipe was also changed twice. The table below shows the genealogy of all Minolta SR 28 mm f/3.5 lenses:
| Name (on lens) | Variant & Generation | years | focal length | max. aperture | min. aperture | elements | groups | filter thread | weight |
| AUTO W.ROKKOR-SG | AR II | 1963–1966 | 28 | f/3.5 | f/16 | 7 | 7 | 67 | 345 |
| MC W.ROKKOR-SG | MC I | 1966–1968 | 28 | f/3.5 | f/16 | 7 | 7 | 67 | 350 |
| MC W.ROKKOR-SG | MC I | 1968–1970 | 28 | f/3.5 | f/16 | 7 | 7 | 55 | 245 |
| MC W.ROKKOR-SG | MC II | 1970–1973 | 28 | f/3.5 | f/16 | 7 | 7 | 55 | 245 |
| MC W.ROKKOR(-SG) | MC X | 1973–1975 | 28 | f/3.5 | f/16 | 7 | 7 | 55 | 260 |
| MC MINOLTA CELTIC | MC Celtic | 1974–1977 | 28 | f/3.5 | f/16 | 7 | 7 | 55 | 260 |
| MC W.ROKKOR | MC-X | 1975–1977 | 28 | f/3.5 | f/16 | 5 | 5 | 55 | 220 |
| MD W.ROKKOR | MD I | 1977–1978 | 28 | f/3.5 | f/22 | 5 | 5 | 55 | 195 |
| MD W.ROKKOR | MD II | 1978–1981 | 28 | f/3.5 | f/22 | 5 | 5 | 49 | 160 |
| MD | MD III | 1981-≈1985 | 28 | f/3.5 | f/22 | 5 | 5 | 49 | 170 |
Adapting
This lens cannot be used natively on any current SLR or dSLRs. To use it in its native environment, you will need a Minolta SR (SR/MC/MD/X-600) film camera. Luckily these are quite easy to find. To use the lens’ full designed capabilities, a Minolta MD-compatible body (any Minolta SR body launched after 1977) is most recommended..
Thanks to being a fully manual lens (manual aperture, manual focus), the lens can be adapted to all mirrorless cameras using a suitable adapter. Moreover, a simple ‘dumb adapter’ will do the job perfectly. Thanks to the popularity of the Minolta SR mount, the availability of adapters to all mirrorless mounts can be taken for granted, on the other hand, specialist adapters (speed boosters, helicoid adapters, tilt/shift adapters) are not available for all mirrorless mounts, but daisy-chaining adapters (e.g. Minolta SR -> Canon EF; Canon EF –> mirrorless) can offer a work-around.
Using Minolta SR mount lenses on dSLRs is also be an option, but it is not trouble-free due to that the Minolta SR mount’s flange focal distance is shorter than that of any dSLR mount (technically with the exception of Olympus’ four thirds mount). Hence, any attempt at adapting Minolta SR lenses must rely on an adapter that uses corrective optics to allow infinity focus. However, such adapters are readily available.
History of Minolta
The company that would eventually develop into the Minolta that manufactured this lens was formed in 1928 as (Nichidoku Shashinki Shōten 日独写真機商店) – a company aiming to produce cameras in Japan using parts (especially shutter mechanisms) sourced from Germany. Initially, the company even employed German camera technicians. During its first years, the company launched several cameras combining locally produced with imported parts. In 1931 the company was renamed Molta Gōshi-gaisha (モルタ合資会社) 6 and soon thereafter the German technicians left the company. The contemporary name Minolta was first used for a camera model in 1933.
In 1937 the company changed its name to Chiyoda Kōgaku Seikō K.K. (千代田光学精工㈱, meaning Chiyoda Optics and Precision Industry Co., Ltd.), and continued to focus on camera manufacture until Japan’s increasing war footing led to the company increasingly focusing on the war effort. After the war Minolta quickly went back to camera manufacture, but as the company also absorbed what used to have been a navy optics manufacture, Minolta suddenly was well placed to produce cameras entirely in house. Hence, the early prewar years saw Minolta both producing TLR’s and folding cameras for medium format film, 35 mm viewfinder and rangefinder cameras, and 16 mm subminiature cameras.
1958 and the birth of the Minolta SLR
In 1958 Minolta introduced the SR-2 single-lens reflex camera. That camera was fairly advanced and utilised many of the technologies and approaches that we today expect from an SLR (pentaprism, instant return mirror, lever winding), but it also introduced a proprietary bayonet lens mount that allowed open-aperture composition and focusing (on compatible lenses). Spurred on by that success, the company in 1962 changed its name to Minolta Camera K.K.
While Minolta in the subsequent decades made many improvements and extensions to the Minolta SR mount, that mount remained fundamentally unchanged until the late 1990s (the last Minolta SR compatible body was introduced in 1995) in that Minolta managed to maintain full forwards and backwards compatibility (you can mount any 1958 Minolta SR lens on a 1995 Minolta X-370s and it would work just as on a 1958 SR-2). Knowing how much other makers (e.g. Nikon) struggled with this, that is not a minor accomplishment.
More details of the internal progression of the Minolta SR mount is given in the JAPB article on the Minolta SR mount.
1985 and Minolta as the forerunner of the AF revolution
In 1985 Minolta beat its entire field of rivals to the punch by introducing the Minolta 7000 AF7 – the world’s first working autofocus SLR body, its attendant line of autofocus lenses, and a new lens mount (the Minolta A or ⍺ mount). In a move that angered anyone who had an investment in Minolta SR lenses8, the new lens mount would not only be different, but also sported a flange focal distance longer than the Minolta SR mount, meaning that existing lenses could not be used at infinity without using an adapter with optics (which leads to both a mild deterioration of image quality as well as a mild teleconversion).
While Minolta still introduced a small number of Minolta SR mount compatible camera bodies after 1985, development of Minolta SR optics and bodies effectively ended as Minolta put all its brawn into making its AF bet a success.
Footnotes
1 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’.
2 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
3 Length is given from the mount flange to the front of lens at infinity.
4 Diameter excludes protrusions such as rabbit ears or stop-down levers.
5 S=straight; R=rounded; C=(almost)circular at all apertures.
6 ‘Molta’ was a contraction of “Mechanismus Optik und Linsen von Tashima” ( Engl: “Mechanism, Optics and Lenses by Tashima”), indicating that German influenced in the company were still quite strong.
7 Minolta is one of those companies that made a habit of naming products differently in different markets, and unless you’re aware of this, it will make your head spin. The Minolta 7000 AF would be called the Maxxum 7000 in the US, and the Alpha 7000 in Japan. More problematically, this would lead to some situations where very similar monikers would be used in different markets for wildly different cameras. Also, those lenses that would carry the name ROKKOR in the rest of the world would regularly be branded ROKKOR-X in the americas
8 Canon would do exactly the same two years later.