This lens is very expensive and really a speciality lens, but if you need it or have a use for it its the best 24mm lens on the market. Ultra sharp right from wide open at f1.4, at f2.8 its sharper than Nikon's 14-24 and Nikon's 24-70.
Accurate focus; Consistent Output; Durable; Easily Interchangeable; Quick Focus; Rugged; Sharp Focus; Strong Construction