Mamiya Mamiya-Sekor C 80mm f/2.8

Hand someone a Mamiya 645 with the 80mm f/2.8 mounted and tell them to shoot a half-length portrait at f/2.8 from six feet. The face comes back sharp, the background dissolves, and the head sits in the frame the way it never quite does on a 35mm fifty. On 6x4.5 the 80mm is the normal lens, the angle of view your eye expects, but it drags medium-format shallow depth of field along with it. You get the framing of a standard lens and the subject separation of a short tele. That pairing is the whole reason the lens turns up on so many studio bodies, and it is what most people are actually buying when they buy a 645.

Wide open it renders cleanly without being clinical. There is a faint softness and a touch of glow at f/2.8 that flatters skin, and contrast firms up as you stop down. By f/5.6 it resolves crisply across most of the frame, and the middle apertures are where it does its best work before diffraction starts pulling detail back on the larger frame. The out-of-focus rendering is smooth and fairly neutral, no swirl, no harsh edges, just a clean falloff that stays out of the way. Color is honest and runs slightly cool on the older coatings. Flare is the weak spot. Point an early non-N copy into a backlit scene and you can lose contrast fast, so a hood is not optional.

The optical layout is a straightforward double-Gauss derived design, the same logic Mamiya leaned on for normal lenses across the line. Build quality is the heavy, all-metal kind that survives being thrown in a bag for thirty years. The 58mm filter thread is shared with several other Sekor C lenses such as the 55mm and the 150mm, so a single set of ND or polarizers goes a long way if you carry more than one focal length.

This is the cheap way into 120. The Mamiya 645 system is the budget entry into medium format, and the 80mm f/2.8 is usually the kit lens that ships with the body, which keeps the used prices low and the supply deep. People cross-shop it against the faster 80mm f/1.9, which buys more separation and costs more, and against Pentax 645 and Bronica glass. For most shooters the f/2.8 is the sensible pick. It is lighter, sharper at common apertures, and a fraction of the cost.

One honest limitation beyond the flare. This lens has no built-in leaf shutter, so flash sync is governed by the body's focal-plane shutter and tops out around 1/60 on the original 645 bodies. If you need high-speed sync with strobes outdoors, look elsewhere. For metering, the 80mm is bright enough to compose and read a scene easily in dim rooms. Set Zone Light Meter to f/2.8 as your working aperture and place the skin tone where you want it. The shallow depth at that aperture means your focus and your exposure both have to be deliberate, not approximate.