Mamiya's affordable 645 tele — the manual-focus Sekor C 150mm f/4 for portraits and landscape.
The Mamiya Sekor C 150mm f/4 is a short-telephoto lens for the Mamiya 645 medium-format system. It is one of the most common tele options in the C-series line, valued as an affordable portrait and general telephoto for the format. It extends the reach beyond the normal and 110mm portrait lenses.
This is a manual-focus lens native to the Mamiya 645 bayonet mount, with a focal length of 150mm and a maximum aperture of f/4. The aperture is set by a mechanical ring on the barrel. The optical design covers the full 645 image circle and keeps the lens relatively compact for its focal length, aided by the modest f/4 maximum aperture.
At 150mm on 645 the field of view is close to a 93-95mm lens on 35mm, giving a longer portrait reach and useful compression for landscape details. The f/4 aperture is enough for subject separation on the large frame while keeping the barrel light and easy to handle. It renders with good contrast and sharpens readily when stopped down a stop.
As a widely produced 645 telephoto, the 150mm f/4 is plentiful and inexpensive on the used market. Check the elements for haze, fungus and internal separation, confirm the aperture blades are dry and snap cleanly, and test the focus helicoid for smooth travel. Inspect the front coating for scratches and verify the bayonet and coupling are tight before buying.