With a diameter of 64.7 millimeters, a length of 54 millimeters and a weight of 375 grams, the lens is similarly compact to the Leica Summilux-M 50 mm f/1.4 ASPH ($4,992 on Amazon). This is despite Sigma integrating an autofocus motor into the weather-resistant housing. The focus ring can also be used to focus manually while autofocus is enabled, without having to switch modes first. The lens also features an aperture ring with an A position for automatic aperture control.
Sigma uses a design comprising nine elements in six groups, including three elements with aspherical surfaces. While the lens is intended to capture very high-contrast and relatively sharp photos, Sigma says the goal of the CL series is not to eliminate all lens aberrations. Instead, the optics were designed to capture images with as much character as possible. The minimum focusing distance is 0.45 meters.