Anamorphic

                

The projection format is used in which a distorted image is stretched  by an anamorphic projection lens to recreate the original  proportional relationship between its width and its height (aspect ratio) on the viewing screen. 

When you use an anamorphic lens, it will stretch the image vertically to cover the entire film frame, resulting in a higher degree of excellence, but will display a very distorted image.

   

Due to a desire for wider aspect ratios,  the development of anamorphic widescreen grew in popularity.   The modern anamorphic widescreen format has an aspect ratio of 2.40:1, meaning the picture width is 2.40 times its height.  

 Pictures are recorded on film so that its full width fits within the film frame, in non-anamorphic spherical (flat) widescreen imaging.  Film frame area is wasted on portions that will be matted out by the time of projection, either on the print  or in the Video Projector, in order to create a widescreen image in the theater.

Anamorphic lens leaves the image on film looking as if it had been stretched vertically.   However,  this deliberate geometric distortion is then reversed upon projection, or Projection TV resulting in a wider aspect ratio on screen than that of the frame as recorded on film.