Mamiya Mamiya-Sekor C 55mm f/2.8

Mamiya built the 645 system in the mid-1970s for the photographer who wanted a bigger negative without hauling a Hasselblad or a press camera. The body ran a focal-plane shutter instead of a leaf, which kept the lenses cheaper and let Mamiya flood the mount with focal lengths fast. This 55mm f/2.8 was one of the early C-series optics, and on the 6x4.5 frame it reads as a moderate wide, close to what a 35mm gives you on full-frame 35mm. Wedding shooters, magazine portrait people, and a lot of working documentary photographers carried one as the lens that stayed on the body when they did not want a normal.

It earns its keep stopped down rather than wide open. At f/2.8 the center is already sharp with good contrast, but the corners stay soft and there is some field curvature, so a flat subject across the frame is not its strength until you close down. By f/5.6 to f/8 it sharpens up edge to edge and resolves the kind of fine detail that justifies dragging a medium-format body around in the first place. The out-of-focus rendering is smooth and well behaved, no nervous edges or swirl, just a clean falloff behind the subject that never fights for attention.

The coating is where this lens shows its age against the later glass. These carry Mamiya's earlier multi-coating, and shot into the light they veil and lose contrast faster than the N versions, which were revised with better coatings (and lighter barrels) from the mid-1980s. Use a hood. Backlit at dusk you can still pull a usable frame, but you are working with a softer, lower-contrast image than a modern lens would hand you, and a stray light source just outside the frame will wash a milky haze across the shadows.

The price is the reason most people land here. A clean 645 C 55mm is one of the cheapest ways into real medium-format wide-angle glass, and buyers cross-shop it against the pricier N version and against the Bronica and Pentax 645 equivalents. The N is sharper into the corners and flares less; the C costs a fraction and renders almost identically once you are at f/8. For black and white documentary and environmental portraits, the difference rarely shows in the print.

One metering habit pays off. At f/2.8 in dim interiors, meter wide open in Zone Light Meter and place your shadows where you want them, because the body has no automatic compensation and these C lenses give you their cleanest character before you stack on too much depth of field. The 58mm front thread takes a standard yellow or orange filter for skies on film, and Zone Light Meter folds the filter factor into the reading so you do not have to do the stop math in your head.