Mamiya's standard 645 normal — the manual-focus Sekor C 80mm f/2.8, the system's workhorse.
The Mamiya Sekor C 80mm f/2.8 is the standard normal lens for the Mamiya 645 medium-format system and the most common lens supplied with the bodies. It belongs to the original Sekor C family and was the default optic on countless M645 and later 645 kits. On the format it delivers a natural, normal field of view.
This is a manual-focus lens native to the Mamiya 645 bayonet mount, with a focal length of 80mm and a maximum aperture of f/2.8. The aperture is set by a mechanical ring on the barrel. The optical design covers the full 645 image circle and is compact and light, making it a straightforward everyday lens for the system.
At 80mm on 645 the perspective is close to a 50mm on 35mm, a neutral view that works for portraits, general shooting and travel. The f/2.8 aperture gives enough subject separation on the large frame while keeping the lens small, and it renders with good contrast and detail when stopped down. Its balance of size, speed and cost made it the workhorse normal for the system.
Because it shipped with most bodies, the 80mm f/2.8 is plentiful and affordable on the used market, which makes it easy to find a clean example. Inspect the glass for haze, fungus and cleaning marks, confirm the aperture blades are dry and close cleanly, and check the focus helicoid for smooth resistance. Look over the front coating for scratches and verify the mount and coupling are sound.