Anamorphic widescreen
Anamorphic widescreen (also called full-height anamorphic or FHA) is a process by which a widescreen image is horizontally compressed to fit into a storage medium (photographic film or MPEG-2 standard-definition frame, for example) with a narrower aspect ratio, reducing the horizontal resolution of the image while keeping its full original vertical resolution.
Compatible play-back equipment (a projector with modified lens, or a digital video player or set-top box) can then expand the horizontal dimension to show the original widescreen image.
This is typically used to allow one to store widescreen images on a medium that was originally intended for a narrower ratio, while using as much of the frame – and therefore recording as much detail – as possible.
One would produce a higher-quality upscaled 16:9 widescreen image by using either a 1:1 SD progressive frame size of 640×360 or for ITU-R Rec.
Other movies (often with aspect ratios of 1.85:1 in the USA or 1.66:1 in Europe) are made using the simpler matte technique, which involves both filming and projecting without any expensive special lenses.
While not anamorphic widescreen per se, many of the earliest Laserdisc offerings forwent the pan-and-scan cropping typical of home releases at the time, the mastering-technicians opting instead to simply squeeze the film's original aspect ratio down to 4:3.
While this resulted in an image that was overly compressed on standard televisions, many later HDTVs can stretch out this picture, thus restoring the correct aspect ratio.
If an anamorphic DVD video is played on standard 4:3 television without adjustment, the image will look horizontally squeezed.
Many modern HDTV sets have the capability to detect black areas in any video signal, and to smoothly re-scale the picture independently in both directions (horizontal and vertical) so that it fills the screen.
However, some sets are 16:10 (1.6:1) like some computer monitors, and will not crop the left and right edges of the picture, meaning that all programming looks slightly (though usually imperceptibly) tall and thin.
