Pentax SMC Pentax 67 1000mm f/8 Reflex

The longest focal-length lens in the Pentax 67 lineup. A catadioptric (mirror) lens rather than a refractive design — uses curved mirrors instead of all-glass elements to fold the long optical path into a much shorter physical lens body. A refractive 1000mm would be impractically long; the reflex design makes 1000mm focal length usable on a hand-mountable lens.

In 35mm-equivalent terms, 1000mm on 6×7 corresponds to roughly 500mm full-frame — extreme telephoto. Used for distant wildlife (birds, large mammals at distance), astrophotography (lunar and solar with appropriate filtration), and highly compressed-perspective landscape work.

Fixed aperture at f/8. Mirror lenses cannot have a conventional iris diaphragm — there's no place to put one in the optical path without occluding the central mirror. To reduce exposure, neutral-density filters are used (typically rear gel-filter slot or a dedicated front filter holder). f/8 is dim for the focal length but typical for catadioptric designs.

Distinctive "donut" out-of-focus highlights are a signature of all mirror lenses — the central mirror occludes the center of out-of-focus point sources, leaving ring-shaped specular highlights. This is either a creative virtue or an aesthetic limitation depending on the photographer.

Mounts on the outer bayonet (Pentax 67 lenses ≥400mm use outer for the additional rigidity needed at long focal lengths and significant weight). Tripod use is essentially mandatory; mirror lock-up plus cable release plus moderately fast shutter speed is the working configuration.