Mamiya's 645 portrait tele — the manual-focus Sekor C 110mm f/2.8 for medium format.
The Mamiya Sekor C 110mm f/2.8 is a short-telephoto portrait lens for the Mamiya 645 medium-format system. It sits above the normal lenses in the C-series line and is widely regarded as a natural portrait focal length for the format. The moderately fast aperture makes it well suited to head-and-shoulders work.
This is a manual-focus lens native to the Mamiya 645 bayonet mount, with a focal length of 110mm and a maximum aperture of f/2.8. Aperture is controlled by a mechanical ring on the barrel. The design covers the full 645 image circle and delivers a longer working distance than the standard lenses, useful for flattering perspective in portraiture.
At 110mm on 645 the angle of view corresponds to roughly a 68-70mm lens on 35mm, a classic portrait length. The f/2.8 aperture yields shallow depth of field on the large frame with smooth background rendering, and detail sharpens well on stopping down. The combination of focal length and speed is why this lens is a mainstay of 645 portrait kits.
The 110mm f/2.8 is one of the more popular 645 lenses and turns up regularly on the used market. Inspect the elements for haze, fungus and cleaning marks, confirm the aperture blades are oil-free and close cleanly, and check the focus ring for smooth, consistent resistance. Look over the front coating for scratches, and verify the bayonet mount and coupling are free of play before purchase.