Mamiya Mamiya-Sekor C 110mm f/2.8

This is the 645 portrait length the catalogs never made famous, and it is arguably the best one in the system. Everybody buys the 80mm because it ships with the body, and everybody who wants more reach jumps straight to the 150mm. The 110mm sits in the gap nobody talks about. On a 6x4.5 frame the crop factor runs around 0.62, so it gives roughly a 68mm equivalent: a normal-plus to mild short tele, long enough to flatter a face and compress the background a touch, short enough to work a tight room without backing into a wall. If you want the classic ninety-ish-millimeter short-tele portrait field, that is the 150mm's job. The 110mm is the one that sits closer to how your eye sees, with just enough length to separate.

Wide open at f/2.8 it renders the way you hope medium-format glass will. The plane of focus lands crisp on the near eye, contrast is moderate rather than biting, and everything behind the subject rolls off into a smooth, unhurried blur. The background stays quiet: no swirl, no nervous double-line edges at the bokeh fringes, just a clean falloff. Skin gets a faint glow at full aperture that softens pores without smearing detail. Stop to f/5.6 or f/8 and it tightens to genuine corner-to-corner resolution, the aperture you want for a full-length figure or a group. Color runs slightly warm and honest on the older coatings, the late-film-era Mamiya signature, not the clinical bite of a modern GF prime.

The optical layout is a documented six-element, five-group construction. Build is the heavy all-metal kind that survives decades of handling. The 58mm filter thread matters more than it looks. It is shared with the 55mm, the 80mm f/2.8, and the 150mm f/3.5 C lenses, so one set of NDs or a single polarizer covers most of a working 645 kit. Carry three primes and you still only feed one filter size.

Where it falls short: f/2.8 at this length does not carve depth the way the 80mm f/1.9 does, so if your whole reason for shooting 645 is the thinnest possible slice of focus, the faster normal still wins. And the one that bites outdoors is that there is no leaf shutter in this lens. Flash sync is governed by the body's focal-plane shutter and tops out around 1/60 on the original M645 bodies, so balancing strobe against bright sun means reaching for ND rather than a faster sync speed. When you load Zone Light Meter for that, the 58mm thread is the number to remember: meter the ambient, dial in the ND factor, and let the sync speed set your floor.

It stays cheap because it is the forgotten focal length in a system the digital crowd abandoned. People cross-shop it against the Pentax 645 120mm and the Hasselblad 100mm Planar, and it usually changes hands for less than either. To my eye it holds its own against both for 6x4.5 portraits, which is why it remains one of the quieter bargains in medium format if you can find a clean copy.