Mamiya Mamiya-Sekor C 127mm f/3.8

This is the lens that came bolted to the front of most used RB67 bodies on the market. The 127mm was Mamiya's normal lens for the system, the one packaged in the kit, which means it is everywhere and it is cheap. On 6x7 the angle of view sits close to a 60mm on full frame, a hair tighter than "standard," and that small extra reach is exactly why it became the default portrait length for a generation of studio shooters who never bought anything else.

Optically it is a workhorse, not a showpiece. Wide open at f/3.8 it is perfectly usable but a touch soft in the corners with some glow on specular highlights; stop down to f/8 or f/11 and it snaps to genuine medium-format sharpness across the frame. The "C" designation matters here. The earlier non-C version (and the interim NB, same optics in a redesigned barrel) was single-coated and flared easily into the sun, while the C is multicoated and holds contrast far better against backlight. Rendering is neutral and slightly warm, the bokeh smooth and unremarkable in the best sense, no harsh edges or onion rings. It will not give you swirl or character. It gives you a clean, big negative.

Who uses it: portrait and product photographers, mostly in a studio, plus a steady stream of people shooting their first 6x7 because the body-plus-127 combo is the cheapest door into the format. The RB67 itself is a bellows-focusing, waist-level, rotating-back tank that weighs more than some laptops, so nobody is taking this lens to a street fight. It lives on a tripod under strobes, and that is where it shines.

Every RB67 lens carries its own leaf shutter, and the 127 is no exception. That means flash sync at every marked speed up to 1/400, which is the whole reason studio shooters love this system. The tradeoff is the slow-speed range and the fact that the shutter is in the lens, so when you meter for mixed ambient and strobe, set your aperture for the flash and let the shutter speed handle the existing light. Zone Light Meter's reflected and incident readings give you the aperture; you dial the leaf shutter speed independently to balance the room. Worth remembering too: because the RB focuses by extending the bellows, close-up work adds real exposure loss, and the app's bellows compensation will tell you how much to open up when you rack it out for a tight headshot.

The honest weakness is corner performance and that wide-open softness, neither of which you will notice at f/11 but both of which show up if you try to shoot it open in low light. People who want clinical edge-to-edge bite at every aperture cross-shop the later RZ-mount 110mm f/2.8, which is a sharper, more expensive lens. But for a few hundred dollars you get a competent normal lens and a 6x7 frame, and that value proposition has kept the 127 in working bags for fifty years. It is not the lens you brag about. It is the lens you actually use.