A method and apparatus for determining a focal-length setting of a lens mounted to a camera. In a method for determining a focal-length of a lens mounted to a camera, a distorted image of a scene is captured. A distortion-correction function is applied on the distorted image or on a portion of the distorted image. A most representative distortion-correction function is identified and a current focal-length setting for the lens is identified by correlating the identification to a data compilation.