Pentax's ultra-wide A-series prime — a manual-focus 15mm f/3.5 with an 'A' aperture setting.
The SMC Pentax-A 15mm f/3.5 is an ultra-wide-angle prime for the Pentax K bayonet mount, from the A-series generation that added the electrical 'A' aperture position for program and shutter-priority automation on compatible bodies. It was the widest rectilinear prime in the A range.
This is a manual-focus lens with a 15mm focal length and a maximum aperture of f/3.5. It carries Super Multi Coating and an 'A' setting on the aperture ring that lets the camera control the diaphragm. Element count and filter details should be confirmed per sample, as ultra-wide designs often use rear or built-in filters.
The 15mm angle of view is very broad and rectilinear, holding straight lines without the bowing of a fisheye. It suits architecture, interiors and dramatic landscapes where a wide sweep and deep depth of field are wanted.
Because it is an ultra-wide prime, used copies come up less often than mid-range lenses and clean glass is prized. Check the front element for wear, look for internal haze or fungus, confirm the aperture is dry, and verify the 'A' position clicks in firmly. It works on Pentax K digital bodies and adapts to mirrorless with an adapter.