The Minolta MC Rokkor 21 mm f2.8is one of the best wide-angle lenses manufactured by Minolta. It is also the first lens whose optical scheme comprised the floating element to provide clear images even when shooting at close and middle distances. In the mid 70's the lens was considered one of the best wide-angle lenses in the range of focal lengths of 20-21mm, its optical performance being inferior only to the Zeiss Distagon 21 mm f2.8.
The mechanical design is of high quality, as is the case with all MC Rokkor lenses. The front element does not rotate on focusing, which enables the use of filters, especially for landscape photography. Close to the aperture ring is a small lever for covering the aperture to control the depth of field. The lens shows good optical performance at f/2.8-f/4. It delivers extreme sharpness and contrast across the frame at f/5.6-f/8.
It is the third lens in the series.
The first version (9 elements in 5 groups) was manufactured in 1962-1966.
The second was manufactured in 1966-1972.