wide-angle lens

Short-focus, wide-angle lenses are usually mounted near the film. Single-lens reflex cameras need a certain minimum lens-to-film distance to accommodate the swinging mirror. Wide-angle (and sometimes normal-focus) lenses for such cameras therefore use retrofocus designs. In these the back focus is appreciably longer than the focal…

…pioneered in the use of wide-angle cameras for determining photographically stellar positions and proper motions (the apparent rates of change of position across an observer’s line of sight), formerly measured by laborious visual methods. Fifteen volumes of the Yale Zone Catalogues, which were prepared under his direction, give results for…

…in optical devices, such as wide-angle lenses for cameras and microscope objectives. The toxicology of germanium and its compounds is poorly defined.