Though containing some of its predecessors' strengths, such as a 19.7-inch close-focus range, this model gives you the slightly larger maximum aperture of f3.8-f5.6 and a lighter weight. The use of aspherical optics and a new mechanical construction in the design can be credited with the reduction in weight. Despite its compact size, just under three inches, this lens maintains the high level of performance for which its predecessors are known. The internal focusing system allows for a nonrotating front barrel, making for the convenient use of filters. This model is dedicated to Pentax AF SLR cameras.