The Sony Sonnar T* coating works with an innovative optical design to suppress internal reflections, for sublime contrast from highlights to deep blacks. In keeping with the Sonnar concept, a large F1.8 maximum aperture can produce beautiful full-frame background bokeh, but you also have the option of stopping down for extended depth-of-field. A bright lens like this is also an advantage when shooting indoors or outdoors in low light. SEL55F18Z