The Summilux-SL 50 mm f/1.4 ASPH. is designed to deliver maximum optical performance and establishes new benchmark standards in terms of sharpness. Thanks to internal focusing, the overall length of the lens remains unchanged when focusing. A special feature of its construction is the motorized focusing system. In contrast to manually focused prime lenses, where the length generally varies when focusing, the Summilux-SL 50 f/1.4 ASPH. has internal focusing. To ensure high imaging performance throughout the entire focusing range, the focusing group is elaborately constructed with an aspherical element, yet remains light enough to guarantee fast automatic focusing. Its optical design contains a total of 11 elements. Of these, two are aspherical elements and a further four are made from glasses with anomalous partial dispersion for the correction of chromatic aberrations. This complex optical construction reduces all monochromatic and chromatic aberrations to a hardly perceptible minimum. Advanced multilayer coating on all lens surfaces, the optimum design of the lens tubes, and the rectangular lens hood provided with the lens significantly reduce reflections and stray light.