The Nikon AF Nikkor 20mm f/2.8Dis a compact wide-angle full-frame prime lens.
The same optical scheme (12 elements in 9 groups) was used in the non-autofocus Ai-S series lens (weight - 10 g lighter, diameter - 4 mm smaller, HK-14 hood), which had been produced since October, 1984. Since February, 1989 the autofocus 20/2.8 lens (without index D) had been produced. In March, 1994 the AF 20/2.8D lens went into production. As opposed to previous models, it was able to transmit distance information to a camera to provide correct functioning of a flash. All these modifications with the 12/9 optical scheme were equipped with the Close-Range Correction (CRC) system.