Mamiya Mamiya-Sekor C 180mm f/4.5

Set the RB67 180mm beside a Pentax 67 165mm f/2.8 and you have the two go-to portrait lenses of medium-format SLR work, but they do the job in opposite ways. The Pentax is faster, focuses on a helicoid, and rides a body you can actually hand-hold. The Mamiya is slower at f/4.5, mounts on a bellows-focusing studio brick, and carries a leaf shutter that flash-syncs at every speed up to 1/400. That sync is the whole reason wedding and studio shooters bought into the RB system to begin with.

On 6x7 the 180mm lands as a short telephoto, roughly what a fast 90mm gives you on full frame. Classic head-and-shoulders length, and the lens was built for that and little else. Wide open at f/4.5 the center is already sharp, with a soft falloff toward the corners that keeps skin looking like skin rather than a pore inventory. Stop down to f/8 or f/11 and the whole frame tightens into the kind of detail you buy a 6x7 negative to get. Contrast sits in the moderate range, not punchy, which is the right call for faces and leaves you room to grade.

The out-of-focus rendering is where this lens earns its keep. You are throwing a 180mm across a 6x7 frame, so subject isolation comes easy even at f/4.5, and backgrounds dissolve into a smooth wash with round highlights and quiet edges. Nothing swirls, nothing fights for attention. It is a clean, even drawing that puts the face forward and lets the bellows handle the separation.

The honest limits are the f/4.5 ceiling and the system underneath it. You are not shooting this in a dark church without a tripod and a patient subject. The leaf shutter tops out at 1/400, so bright daylight wide open means stacking an ND on the 77mm thread. As for flare, the later K/L line is generally credited with better control thanks to improved coatings, so the early C wants a hood and a careful eye when a window or the sun sits near the frame edge.

Here is where the RB trips up people coming from 35mm. The camera focuses by extending its bellows, not by shifting glass inside the lens, so pulling in for a tight head shot physically lengthens the lens-to-film distance and costs you real light. The loss grows the closer you focus, often around a half to a full stop at portrait distances and more once you reach the close-focus limit near 2.8 feet. Zone Light Meter computes that bellows extension factor for you, so you meter the scene and let the app fold the correction in instead of doing the math between frames.

Today the C is one of the cheapest doors into genuinely large-negative portraiture. The K/L commands a premium for its coatings, while the C trades for less than a fast 35mm fifty and resolves more than enough for prints a 135 negative cannot touch. People still buy it because there is no shortcut to a 6x7 frame, and this is the lens Mamiya designed to fill it with a face.