Konica's fast AR ultra-wide — the 21mm f/2.8 Hexanon, a stop brighter than the f/4.
The Konica Hexanon AR 21mm f/2.8 was a fast ultra-wide prime for the Konica AR bayonet used on Konica's Autoreflex SLRs. It sat at the wide end of the AR system as the brighter sibling to the f/4 version, giving an extra stop for photographers who wanted a viewfinder that stayed easy to compose in low light.
This manual-focus Konica AR lens has a 21mm focal length and a maximum aperture of f/2.8, a full stop faster than the f/4 variant. It is a rectilinear ultra-wide that keeps straight lines straight. Details such as element count, filter size and minimum focus distance are not verified here and are left out rather than guessed.
The extra brightness makes the 21mm f/2.8 more usable indoors and at dusk, where its broad, corrected field takes in whole rooms and streetscapes. It suits architecture, interiors and travel reportage, and stopped down a stop or two it renders wide scenes with even sharpness across the frame.
The faster 21mm is scarcer and more sought-after than the f/4, so expect a premium when one appears. Look closely for internal haze, separation and coating scratches on the large front element, confirm the diaphragm is oil-free and check the helicoid feel. Mirrorless adaptation is straightforward via an AR adapter; DSLR use is limited by the AR flange distance.