Mamiya's updated RB67 normal — the leaf-shutter K/L 90mm f/3.5 with improved coatings.
The Mamiya Sekor K/L 90mm f/3.5 is the updated standard normal lens for the Mamiya RB67 medium-format system, part of the K/L generation introduced around 1990. It replaced the earlier C-series 90mm with a revised optical design and improved coatings. On the 6x7 frame it delivers a natural normal field of view.
This is a manual-focus lens native to the Mamiya RB67 bayonet mount, with a focal length of 90mm and a maximum aperture of f/3.5, marginally faster than the earlier C version. It carries a built-in leaf shutter, with the aperture set on the barrel and focusing by the camera bellows. The K/L formula was intended to raise contrast and control flare over the older design.
At 90mm on 6x7 the perspective is close to a 44mm lens on 35mm, a neutral normal view suited to portraits and general work. The improved K/L coatings help with contrast in challenging light, and the leaf shutter provides flash sync at all speeds for studio and fill-flash shooting. It became the preferred standard lens for later RB67 users.
The K/L 90mm f/3.5 is later and better specified than the C version, so it usually commands a higher price. Test the leaf shutter across the full speed range for clean firing, and check the glass for haze and fungus. Confirm the aperture blades are dry and close cleanly, and verify the bayonet and shutter-cocking coupling engage correctly before purchase.