Pentax SMC Pentax 67 800mm f/4 ED [IF]

Extremely rare super-telephoto — the longer, faster sibling to the 600mm f/4 ED. In 35mm-equivalent terms, 800mm on 6×7 corresponds to roughly 400mm full-frame. f/4 maximum aperture at 800mm focal length on medium format places this among the most light-gathering super-telephotos ever built for any system.

Production was very limited — the lens was effectively built-to-order for specialized professional and institutional users (astronomy, professional sports, scientific imaging). Several examples are known to have been used at the Olympic Games and other major sporting events during the 1980s and 1990s. Most production examples remain in institutional or private collector hands and rarely appear on the open market.

ED glass plus internal focusing (IF) plus a refractive (non-catadioptric) design — the optical specification matches the 600mm f/4 ED scaled up. Mounts on the outer bayonet. Massive size and weight; requires a heavy tripod with appropriate gimbal head, and a mounting collar on the lens itself rather than the body for proper balance.