The native resolution of a liquid crystal display (LCD), liquid crystal on silicon (LCoS) or other flat panel display refers to its single fixed resolution. As an LCD consists of a fixed raster, it cannot change the resolution to match the signal being displayed as a cathode-ray tube (CRT) monitor can, meaning that optimal display quality can be reached only when the signal input matches the native resolution. An image where the number of pixels is the same as in the image source and where the pixels are perfectly aligned to the pixels in the source is said to be pixel perfect.