Guide to Anamorphic Widescreen DVD

Overview

• The most common display aspect ratio standards are 1.33:1(4:3), used with VHS on 20^th century standard definition CRT televisions or 1.78:1 (16:9), used with modern high definition and widescreen LCD displays.
• Standard aspect ratios for film are 1.85:1 or 2.35:1

Common methods of conversion include:

• Enlarging the original image by the same factor in both directions to fill the display and cutting off any excess picture information. This is commonly known as 'zooming and cropping' or pan and scanning'.
• Adding horizontal mattes (letterboxing) or vertical mattes (pillarboxing) to retain the original film aspect ratio.
• Stretching the image to fill the display through scaling by different factors in both directions. This leads to distortion of the picture and should be avoided if at all possible.

Unfortunately, DVDs became popular just prior to the switch from the older 4:3 display standard to the modern 16:9. This led to some confusion and multiple standards, especially with older DVD releases.


Anamorphic vs. Non-anamorphic

• Non-anamorphic (letterboxed) sources use hard-coded black bars to create frames that display a 4:3 picture. As the film's aspect ratio increases, more and more of the scan lines are devoted to the black letterbox bars at the top and bottom of the video frame instead of reproducing picture information. This reduces the amount of picture detail that can be displayed. Up to 33% of the data can be storing black pixels rather then actual video information.
• An anamorphic source has little to no hard coded black bars, and works stretching the image vertically to create the 4:3 aspect ratio instead. This data is digitally processed by the display device. A 4:3 display will combine horizontal rows and add letterboxing bars. A 16:9 display stretches the original square pixels into rectangles, restoring the original aspect ratio without loosing any resolution.
• Generally on a computer, the raw source will play in a window and only be adjusted when in fullscreen. If there are bars when viewed in a window, it is likely a non-anamorphic source.