Pentax DA645 28-45mm F4.5ED is an Auto Focus (AF) Wideangle Zoom lens with 645 max sensor coverage. When mounted on a 645 sensor camera, it will give you an FF equivalent focal range of 21.84mm. With the max aperture of only f4.5 at 28mm, it is considered a slow lens.
This lens features on optical image stabilization which helps capturing sharper images at lower shutter speeds. Pentax DA645 28-45mm F4.5ED is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.