Widest wide angle lens in Konica line-up.Image and built quality both are excellent. Due huge front element size, lens is a bit prone to flare.
Rare lens, not easy to find it, it has several versions. I know two of them , earliest with chrome nose and later one with all black metal finish.
Lens is sharp from edge to edge.
Lens is usable with Konica AR cameras and with mirror lens digital cameras micro 4/3, Sony-NEX, Samsung NX with conversion usable on 4/3 too. If you have a chance to get it don't convert it rather buy a compatible analog or digital camera body.
My favourite lens is the 21mm. I got it very cheaply with its original lends hood and leather case in perfect condition. There's a little loss of sharpness towards the extreme corners but it's a cracking lens.
The Hexanon / Hexanon AR 21 mm / F4 is of very good optical quality and renders sharp images with high contrast. Vignetting is visible with this exteme wide-angle lens, but is not too disturbing. Distortions are corrected very well, although there are pincushion distortions detectable with straight lines running parallel to the frame â€“ the extreme wide-angle effect is always clearly visible, however. The faster successor model is said to have better sharpness, but I have no own experiences with this lens.
Due to its huge, not recessed front element, the Hexanon / Hexanon AR 21 mm / F4 is a bit prone to flare. With its huge field of view, the sun is frequently lying in or just outside the image. Therefore you should use the original lens hood if possible, which was delivered with the lens. It gives much better protection than a collapsible lens hood, that gives almost no shading with the big diameter and the wide image angle. The original lens hood covers those parts of the front element that are outside the image area on the film, leaving open a rectangular opening . The precise aligning is ensured by a groove in the lens barrel with a corresponding feather in the hood.
The viewfinder image is a bit dim with the widest aperture of 1:4, in low lighting split-image or microprism focusing aids tend to black out â€“ precise focusing is a bit tricky under these circumstances.
When new, the Hexanon / Hexanon AR 21 mm / F4 was quite an expensive lens, because of its extreme focal length it is quite rare and difficult to find. As a rare collector's item, it tends to fetch high prices nowadays. On the other hand, due to its extreme focal length and its very strong wide angle effect, possible use is somewhat limited. Whether the high price can be justified, is a matter of your personal needs. If you find yourself having much use for this focal length, the Hexanon / Hexanon AR 21 mm / F4 will serve you well.(buhla.de)