Mamiya Mamiya-Sekor K/L 90mm f/3.5 L

Put a strobe pack behind a 1/400 shutter and a focal-plane camera quits on you somewhere around 1/250. The RB67 does not care. This is the lens that owns the cross-lit studio portrait and the flash-fill outdoor headshot, because the shutter lives inside the barrel and syncs flash at every marked speed, all the way up. Overpower the sun at f/22 and 1/400 with a single head, drag the ambient down to nothing, and the 90mm sits there and renders it: full contrast, clean specular highlights, no sync banding eating the frame. That is the job a leaf-shutter normal lens on a 6x7 body was built for, and it is the reason wedding and commercial shooters kept these in rotation long after 35mm went autofocus.

The 90mm is the standard lens for the format, roughly a 44mm equivalent in full-frame terms, so it sees about the way your eye does. The K/L designation is the later revision, a genuine optical recompute with a floating element and refreshed multicoating over the C-series glass it replaced. The C was already multicoated, so the gain here is the formula and the newer coatings, not a jump from single to multi. Where it shows is the deep-stack flare: shoot into a window or a hard rim light and contrast stays put, the way the original single-coated non-C glass never could. Wide open at f/3.5 it is already sharp across the central field, plenty for skin and catchlights, and by f/8 to f/11 it is biting corner to corner on a 6x7 negative. The out-of-focus rendering is smooth and well-behaved behind a face. No nervous edges in the background, no cartoon outlining of branches against the sky.

Where it bites you is mass and tempo. The whole rig is a brick. The RB67 plus this lens is a two-handed, tripod-or-monopod proposition, and the bellows focusing that makes the body so flexible also makes you slow. You compose, you focus the bellows, you fire one frame, you cock the shutter and mirror together with the body lever, then wind the film on the back separately. Ten exposures and you reload. This is a deliberate, locked-down, one-frame-at-a-time instrument, and if you fight that you will hate it.

That bellows is also the trick worth knowing. Because the RB67 focuses by extending the body, the 90mm racks to genuine close distances with no extension tube at all, and at those distances you are losing light to the longer draw. The Zone Light Meter app computes the bellows extension factor for you, so when you bring this lens in tight on a product shot or a portrait detail, meter the scene and let it fold the compensation in rather than guessing a half stop. The 77mm front thread takes standard ND and grad filters cleanly if you are working long exposures or holding back a sky.

Today these sell cheap relative to what they do. People cross-shop the RB system against the Pentax 67 and the Mamiya 7, and the RB wins on flash and bellows close-focus while losing on portability. If you have decided you can live with the weight and the pace, the K/L 90mm is the one to start with, and you will rarely have a reason to take it off.