The smc DA 50mm f/1.8 Lens from Pentax is a fast f/1.8 lens for cameras with a Pentax K mount. In full-frame (35mm) format, this is considered a "normal" lens. Mounted to a camera with an APS-C sensor, this lens gives an angle of view equivalent to a 76.5mm telephoto lens--ideal for portraits. The wide f/1.8 aperture makes this an essential lens for working in low light, and it also delivers beautiful bokeh (the out-of-focus portion of a photograph). This lightweight (4.3 oz) lens is very compact--just 1.5" (3.8 cm) long. The addition of Pentax Super Protect (SP) coating to the lens helps prevent dust, water, grease and other substances from attaching themselves to a lens and degrading image quality.