The Pentax smc FA 645 45-85mm f/4.5 Lens is a standard zoom lens capable of wide angle to short telephoto focal lengths equivalent to 35.5-67mm in 35mm format. The maximum f/4.5 aperture is constant throughout the zoom range, and it can stop down to a minimum of f/32. This is due in part to a lens construction of 11 elements in 9 groups.
During use, you can switch between auto and manual focus by simply sliding the focus ring forward or backward. It can even focus down to a minimum of 1.6' away. Further benefiting image quality is an eight blade diaphragm that will ensure smooth out-of-focus areas. It also comes with a case and has a 77mm front filter thread.