Rokkor Tales: Minolta's Fab Fifty-Eights

MC-II generation (1969-1973) versions of the 58/1.4 (left) and the 58/1.2 (right) on SRT-101s from 1970

    The 58mm focal length is inextricably tied to the introduction of the 35mm SLR in the mid-1930s. This was due entirely to the physical difference in construction required by the mirror (the "reflex" part of the Single Lens Reflex designation) used for viewing the subject directly through the lens versus the then-standard rangefinder design. Because of the greater depth that including the mirror in the optical path required, this entailed more distance between the rear of the mounted lens and the film plane, which is termed "back focus". The longer back focus of the SLR meant that the standard 50mm focal length rangefinder lenses of the day could not bring the rear focus node to the proper distance from the film plane if simply converted to the SLR mount (in this case, the Kine Exakta of 1936). By the mid-1960s, 50mm would become the standard for SLR lenses as optical designers were able to gradually overcome the design challenges presented by the SLR. In the meantime, the easiest way to overcome the back focus issue was to simply bump the focal length a bit to accommodate the extra back focus. And that is what Willy Merte of Zeiss did in developing the famous 58mm f/2 Biotar, released in 1938. The Biotar would set the bar for standard SLR lenses for the next 25 years, famously duplicated in the Helios 44-2, among others. Most manufacturers of SLR lenses followed Merte's lead by producing 55 to 58mm lenses, particularly for faster-than-f/2 maximum apertures. Minolta was no exception, and would, in fact, be the last holdout among the Japanese manufacturers when it came to adopting 50mm as its normal lens focal length. They introduced their fast 58/1.4 only three years after their first SLR, the SR-2, and supplemented it with a 58/1.2 seven years later. The 58/1.4 would remain in production until 1973, and the 58/1.2 until 1978, with both being replaced by 50mm lenses, accordingly. This is their story.  

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