The Sigma 105 mm is a telephoto prime macro lens, which has the focal length of 105 mm and the image circle of 35 mm. The maximum aperture value of the Sigma lens has the value of f/2.8 while the minimum aperture stands at f/22 and it could be easily used for macro photographs. Although the Sigma 105 mm does not have front element rotation, it does include focus limiter and HSM that comes equipped with full-time manual override as well as image stabilization. The diagonal angle of view of the Sigma lens is 23.3 degrees while its magnification ratio is 1x or 1:1. As far as the construction of the telephoto prime macro lens is concerned, it consists of 16 elements, which have been arranged into 11 groups, and there are nine rounded diaphragm blades. The dimensions of the Sigma 105 mm are 5.0 inches by 3.1 inches and it weighs 25.6 oz. The mounts available are compatible with Pentax, Sigma, Canon, Sony, and Nikon single lens reflex cameras.