One early attempt to address the lack of a good "fast" lens for portraiture, and the subject of the first US patent for photographic apparatus, was Alexander Wolcott's camera, which used a concave mirror instead of a lens and operated on the principle of the reflecting telescope. The mirror was fitted at one end of the camera and focusing was done by adjusting the position of the plate in a holder that slid along a rail. Designed solely for portraiture, this arrangement produced a far brighter image than a Chevalier lens, or even the later Petzval lens, but image quality was only marginal and the design was only practical for use with small plates.