Mamiya-Sekor SF C 145mm f/4 Soft Focus (645)

The SF C 145mm f/4 is the soft-focus portrait lens of Mamiya’s manual-focus 645 system, a 90 mm equivalent on 35mm film. Mamiya’s Sekor C instruction sheet says it was designed with major emphasis placed on portraiture: the soft-focus effect is varied continuously by rotating the Softness Control Ring and the aperture ring, and by stopping down to f/8 or smaller it becomes a normal lens with sharp images. Japanese Wikipedia and the English Wikipedia table agree on 7 elements in 5 groups, a closest focus of 1.5 m and a 77 mm filter thread; the English table adds f/4 to f/32, eight aperture blades, a screw-in hood, 116 mm by 82 mm and 900 g, which makes it the heaviest 645 prime short of the 300s. The sheet lists its hood among the special ones that cannot be borrowed from another lens of the same thread.

It has one version and no date. camera-wiki lists ‘C 145mm f4 soft focus’ among the original C lenses, Mamiya’s sheet of the 645 Super years still carries it, and the 645 Pro TL instruction book of 1997 does not, its special-effect lenses being the fisheye, the shift, the two macros and nothing soft. So the year here is the C line’s start with the M645 in June 1975, a floor, and the end falls between the Super and the Pro TL. No N barrel is recorded anywhere consulted. The RB67’s SF C 150mm f/4, a five-element leaf-shutter lens with three diffusion discs, is the design’s cousin on the larger format and is not a version of this lens; seller titles and search results confuse the two constantly, which is why 150mm titles are excluded from this page’s listings.

No published review was found by the searches made for this page; what surfaced were forum posts from owners who describe the range of effects available from the softness setting and the aperture together, and dealer listings repeating the specification. The mechanism is the one Mamiya describes for the RB67’s 150mm f/4 soft focus on its Pro SD lens page, designed-in spherical aberration at apertures from f/4 to f/8 that makes images ‘appear sharp at the same time’, with completely sharp normal images at f/8 and smaller; the 645 lens adds the ring and drops the discs.

When buying, turn the Softness Control Ring through its full travel and confirm the aperture ring still clicks at every stop, since the two interact; check for haze between the many groups, which a soft-focus lens disguises on the focusing screen; and make sure the dedicated hood is present, because the 77 mm hoods of the zooms are the wrong length. What remains open: the launch year and the discontinuation year, the softness ring’s scale (forum posts speak of settings 0 to 3, which no document consulted confirms), a list price in any currency, and an independent test.