This is a digital reincarnation of Pentax's unique, full-frame, 17-28mm f/3.5-4.5 fisheye zoom of the mid-1990s. It's the only current zooming fisheye and the first Pentax lens to use a newly developed SP (Super Protective) coating on its front element. As with most fisheyes, the front element of this 10-17mm (a 15-26mm equivalent, due to the 1.5X 35mm lens factor on Pentax DSLRs) bows out in front of the barrel, leaving its arched glass surface unusually exposed. Pentax claims that its SP coating, applied using a new evaporation process, improves surface resistance to water and finger oils, making it easier to clean. Still, beware of scratches!