Mamiya Mamiya-Sekor Z 90mm f/3.5 W

On 6x7 a 90mm reads as the normal lens, a hair longer than true normal, which is exactly why it flatters a face without the squeeze of a portrait tele. That is the whole pitch. It sees roughly what your eye sees, so it became the default glass on the RZ67. Open an old kit and the 90mm is usually still mounted, because there is rarely a reason to take it off.

Wide open at f/3.5 it is already sharp across most of the frame, with the gentle falloff that makes the RZ a portrait machine. Stop down to f/8 or f/11 and it snaps into corner-to-corner resolution, the kind that ate up Velvia and Provia in product and catalog work. The out-of-focus rendering is smooth and unbusy, no nervous edges, which is what you want when a hairline of sharpness across the eyes sits in front of soft seamless. Contrast is moderate and the color is neutral. It does not punch the way some people remember Zeiss glass punching, but that restraint is the point: it stays honest, so beauty and catalog shooters trusted it for years.

The defining feature is mechanical. Like every RZ67 lens, the 90mm carries its own leaf shutter, which gives flash sync at every speed up to 1/400. You can drag the ambient with a 1/8 second exposure and still freeze the subject on a single pop, or overpower midday sun at 1/400 if you have the watt-seconds. When you are mixing flash and daylight, set the leaf-shutter sync speed in Zone Light Meter and read the ambient separately. The 77mm front takes standard ND grads and polarizers without a step ring.

The honest weakness is the system, not the glass. The RZ67 is a brick. Body, prism, and lens push past two and a half kilos together, and the leaf shutter has to be cocked by the body's film advance, so a dead battery or a back-to-body desync leaves you staring at a black frame. This is a tripod lens. Hand-hold it all day and your wrist will let you know, and nobody bought this format for run-and-gun anyway.

Today the 90mm is the cheapest serious way into 6x7. An RZ kit trades for a fraction of a Hasselblad 80mm Planar setup. One buying note worth knowing: the W on the barrel does not mean a later or better-coated version. It just means the aperture ring is marked in half-stops. Optically the W and non-W are the same lens, so do not pay a premium chasing the letter. People cross-shop this against the Pentax 67 105mm, which is lighter and focal-plane shuttered but gives up the all-speed flash sync. If you shoot people under strobes and want the biggest negative your money will buy, the math still lands here.