Mamiya Mamiya-Sekor C 90mm f/3.8

Most RB67 bodies left the factory with this lens screwed on, and there's a reason for that. On the 6x7 frame the 90mm reads as a true normal, closer to a 45mm on 35mm, with enough working room that you don't crowd a head-and-shoulders portrait. The common alternative is the 127mm, which portrait shooters often prefer for its slightly longer reach and the way it sits a touch back from the subject. Plenty of RB owners keep both. But the 90 is the one the kit was built around, and it's usually the lens that comes home first when you buy a body secondhand.

Optically it's classic Mamiya. Acutance is high, color sits neutral, and contrast stays controlled instead of crushing into the shadows. Wide open at f/3.8 the center is already working, with the edges firming up by f/8, which is where most RB shooters live anyway given the depth of field on a frame this size. By f/11 to f/16 it's very sharp across the field, and on a drum-scanned or well-enlarged 6x7 negative that resolution is the whole point of hauling the body around. The out-of-focus rendering is smooth and a little flat. No swirl, no busy edges. Commercial and portrait people love that quiet background; anyone hunting character bokeh will be bored stiff by it.

The glass sits in a leaf-shutter barrel, and that's the system's real advantage in a studio. The shutter lives in the lens, so flash syncs at every speed, top to bottom. For strobe work and for daylight fill at wide apertures that's a genuine edge over focal-plane medium format, where you're pinned to a 1/60 or 1/125 X-sync. The geared speeds run from 1 second to 1/400. Anything longer than a second happens on the T setting, where you open the shutter, time it by eye or by watch, and close it yourself. The diaphragm, for the record, is fully automatic with a depth-of-field preview lever, so you focus and shoot without stopping down by hand between frames.

This is the C generation, the multicoated version that replaced the earlier single-coated 90mm. It handles flare better, though a deep hood on the 77mm front is still smart with the sun anywhere near the frame. Mamiya later released a KL with reworked glass that resolves a little higher under a loupe, but projected or printed at sane sizes the difference shrinks to almost nothing, and the C costs less. That's where it lands now: cheap, everywhere, and built like a vault.

The honest weakness isn't the optic, it's the operation. The body is heavy. You focus by racking the bellows, you cock the leaf shutter as a separate motion, and the whole sequence is deliberate by design. For tripod work this is fine, even meditative. For anything candid it's slow. One metering note that matters on this camera: when you rack the bellows out for a tight portrait or close focus, extension steals light fast, and an uncorrected reading can underexpose by a stop or more. Zone Light Meter computes the bellows factor for you, so the exposure you meter is the exposure you actually get on the film.