Sigma 135mm f/1.4 DG Art, model A025, is a prime telephoto lens for full-frame mirrorless cameras, available for Sony E and L-Mount. Introduced as the first autofocus 135 mm lens with an f/1.4 maximum aperture, it is primarily designed for portraiture, fashion, weddings, events, and available-light photography, where the combination of a long focal length and wide aperture provides pronounced subject separation from the background. The optical design consists of 17 elements in 13 groups, including four FLD elements and two aspherical elements, engineered in particular to control axial chromatic aberration and loss of sharpness at maximum aperture. Focusing uses a floating system with two independent lens groups, each driven by an HLA linear motor, a configuration known as Dual HLA and developed to move the large optical elements quickly and accurately. The diaphragm uses 13 rounded blades, minimum focusing distance is 1.10 m, maximum magnification ratio is 1:6.9, and the filter thread measures 105 mm. The lens includes an aperture ring with lock and click/de-click operation, two programmable AFL buttons, dust- and splash-resistant construction, and a water- and oil-repellent coating on the front element. The supplied hood features a push-button locking mechanism and is made from carbon-fiber-reinforced material. Dimensions are approximately 111.7 × 135.5 mm with a weight of 1,430 g for the L-Mount version and 111.7 × 137.5 mm with a weight of 1,420 g for the Sony E version. Sigma 135mm f/1.4 DG Art is therefore a large, specialized lens primarily intended for portrait work and situations where an f/1.4 aperture, high resolving power, and pronounced background blur are priorities.