File:DVD-Video enhancement using anamorphic lens.png

English:
Increasing the resolution of 2.35:1 widescreen video on a en:DVD disk by eliminating wasted en:pixels due to en:letterboxing. This is normally possible only with a front projector.

1) While anamorphically-enhanced DVD-Video contains no wasted resolution for 16:9 (1.78:1) videos, the use of black bars or mattes is necessary for wider formats such as 2.35:1 movies which are too wide to fit into the 16:9 frame. The display device would display these black bars as if they were a part of the video, wasting some of the device's native resolution.

2) To overcome the wasted resolution, the video is scaled (stretched) vertically, eliminating the black bars. This vertical stretch, via pixel en:interpolation, is performed by a video processor which is either a built-in component of the projector or an external model such as a en:Home theater PC. The image, however, becomes distorted in the process and needs to be corrected.

3) To restore the original aspect ratio, an anamorphic lens is placed in the light path of the projected image. The lens uses either vertical compression (VC) or horizontal expansion (HE). Since the lens works optically, the increase in vertical resolution is preserved. In addition, the en:luminance is altered: vertical compression increases the brightness of the video, while horizontal expansion decreases it.