Tokina's RMC 400mm f/5.6 — a multi-coated Japanese M42 long-telephoto prime.
The Tokina RMC 400mm f/5.6 is a Japanese long telephoto prime made in M42 mount by Tokina. The RMC designation marks Tokina's Rectangular Multi-Coating, and this 400mm was a long reach lens in their screw-mount range for distant subjects.
This is a manual-focus M42 screw-mount lens with a 400mm focal length and a maximum aperture of f/5.6, carrying Tokina's RMC multi-coating. Focus is by hand over a long helicoid, with an automatic diaphragm. It is a large all-metal telephoto, often supplied with a tripod mount. Detailed element figures are not asserted here beyond the verified focal length and aperture.
At 400mm f/5.6 the lens gives long reach for wildlife, sport and distant landscape detail, with the moderate aperture keeping it manageable for its length, and the RMC coating aiding contrast and flare control. As a refractive design it renders cleanly stopped down and is best used on a tripod or monopod for sharp results.
Used copies are affordable relative to Western long lenses. Inspect the long barrel for internal haze and fungus, confirm the aperture blades are clean and oil-free, and check the focus over its long travel and the tripod mount. Verify the M42 mount before purchase. An M42 adapter allows long-lens use on mirrorless with a firm support.