"With the incorporation of PENTAX-original HD coating and the PENTAX-innovated lens-installed SR (Shake Reduction) mechanism, this medium-telephoto lens assures bright, velvety imagery that is ideal for portrait photography. Medium-telephoto lens When mounted on a PENTAX 645D medium format digital SLR camera body, this medium-telephoto lens offers a focal length of approximately 71mm (or approximately 65mm when mounted on a PENTAX 645 film-format camera body) in the 35mm format. This is the first lens to incorporate the PENTAX-innovated SR (Shake Reduction) mechanism within the lens barrel. This mechanism effectively compensates for camera shake up to approximately 3.5 shutter steps and assures the user sharp, blur-free images, even under conditions prone to camera shake, such as hand holding, poorly lit locations and photographing scenes at or near dusk. Dust proof and weather-resistant construction"