Mamiya Mamiya-Sekor C 150mm f/3.5

Skin looks right on this lens before you have done anything to it. The 150mm f/3.5 renders faces with a gentle roll-off from sharp to soft that flatters without going mushy, and the out-of-focus background behind a head-and-shoulders frame goes to a clean, quiet blur rather than nervous edges. That rendering is the point of the lens. On the 645 format a 150mm works out to roughly a short telephoto, the medium-format equivalent of an 85mm or 90mm on 35mm, which is the classic portrait length. Mamiya built it as the standard tight-portrait optic for the M645 system and sold it for the better part of twenty-five years.

It is sharp, but it is honest about how it gets there. Wide open at f/3.5 the center is already crisp and the corners are soft, which on a portrait is a feature, not a flaw. Stop down to f/8 or f/11 and the whole frame snaps into the kind of resolution that holds up to a 16x20 print. Contrast is moderate, leaning toward the cooler, slightly lower-contrast Mamiya house look rather than the punchy Zeiss rendering you get from a Hasselblad system. That lower contrast is part of why the highlights on a face stay smooth instead of going chalky.

The f/3.5 maximum aperture is the catch, and it is worth saying plainly. This is not a fast lens. Indoors without flash, or shooting at dusk, you run out of light before you run out of subject. If you need more speed, Mamiya's own 150mm f/2.8 A covers the same focal length on the same mount, though it costs more, weighs more, and takes a 67mm filter instead of 58mm. For most studio and outdoor portrait work the f/3.5 is plenty. The f/2.8 only earns its keep in low light, or when you want even thinner depth of field.

This particular lens has no leaf shutter, so on an M645 body you are stuck with the focal-plane sync of about 1/60. Mamiya's leaf-shutter 645 lenses sync to 1/500, but the plain f/3.5 C is not one of them, so to balance strobe against bright sun with this lens you reach for ND rather than shutter speed. The 58mm filter thread is the number to remember when you load Zone Light Meter for that kind of work; meter the ambient, dial in the ND factor, and let the focal-plane sync speed set your floor.

People still buy this lens because it is one of the cheapest routes into genuinely good medium-format portraiture. Used copies turn up for a fraction of what the equivalent Hasselblad or Pentax 67 portrait glass costs, and the gap in image quality is far smaller than the gap in price. The usual cross-shop is the Pentax 645 150mm or the Hasselblad 150mm f/4 Sonnar; the Mamiya gives up a little build prestige and resale value, not much else. If you want to shoot 6x4.5 portraits on a budget without buying a wall of glass, this is the lens that keeps getting recommended, and the recommendation earns it.