This is one of the best macro lenses out there. It produces sharp images and great creamy bokeh. It's quite difficult to find one in PKA mount, definitely a keeper lens! There are several variations of this lens, all sharing the same optical formula, 6 elements /6 groups: Lester A Dine 105mm f2.8, Vivitar 100mm f2.8, and Kiron 105mm f2.8.