Pentax SMC Pentax 67 90-180mm f/5.6

The second of two zoom lenses in the Pentax 67 system (the other being the 55-100mm f/4.5) — the normal-to-tele zoom covering the range from approximately the 105mm f/2.4 normal through the 165mm f/2.8 short tele.

A constant-aperture f/5.6 zoom — substantially slower than the prime equivalents at any focal length, but the only zoom option in this range for the Pentax 67. In 35mm-equivalent terms, 90-180mm on 6×7 corresponds roughly to 45-90mm full-frame, covering the normal-through-portrait range typical for portraiture and environmental shooting.

The f/5.6 maximum aperture is the lens's primary practical limitation — for available-light portraiture or any handheld work in dim conditions, the prime alternatives (105mm f/2.4, 165mm f/2.8) offer 2-3 stops more speed. Most useful in well-lit conditions or on tripod where the framing flexibility of the zoom outweighs the speed disadvantage.

Released in the early 1990s during the Pentax 67 era. Mounts on the inner bayonet; 67mm filter thread. Scarcer on the used market than the 55-100mm zoom or any of the prime lenses.