The Loxia 21mm f/2.8 from ZEISS is a sleek wide-angle prime, designed for full-frame Sony E-mount mirrorless cameras. Based on the Distagon optical concept, this lens uses four anomalous partial dispersion elements and one aspherical element to provide a marked reduction in chromatic and spherical aberrations for improved color rendering, sharpness, and clarity. For minimizing flare and ghosting, an enhanced ZEISS T* anti-reflective coating has also been applied to benefit working in difficult lighting conditions. Loxia lenses are also characterized by their compact form factor and all-metal lens barrel, which incorporates engraved focusing and depth of field scales, for fine-tuned control. Wide-angle prime is designed for full-frame Sony E-mount mirrorless cameras, however, can also be used with APS-C models where it provides a 31.5mm equivalent focal length. Bright f/2.8 maximum aperture suits working in available-light conditions and is also well-suited for astrophotography use. Four anomalous partial dispersion elements are used to significantly reduce color fringing and chromatic aberrations for increased clarity and color fidelity. One aspherical element controls distortion and spherical aberrations in order to produce greater sharpness and more accurate rendering. Manual focus design is benefitted by focusing and depth of field scales along with a 90° focus ring rotational angle and hard stops at both infinity and minimum focusing positions. The manual aperture ring has clicked indicators throughout the aperture range.  Weather-resistant construction includes internal seals to guard against dust and moisture as well as a blue sealing ring at the lens mount to protect the lens-camera interface. The lens mount is fitted with an electronic interface that conveys all lens Exif data to the camera and can also be configured to automatically activate the camera's focusing magnification function when turning the focus ring.