Standard definition picture information takes up a certain number of pixels. That number was optimized for 4x3 display. Anamorphic and letterbox are two ways of getting a 16x9 visual aspect ratio to fit in a medium built around 4x3.
A 16x9 visual aspect ratio can fit either of these two ways.
1. Squish the picture information so when viewing it in the standard mode on TVs everything looks tall. ANAMORPHIC. A nice widescreen switchable TV will make this look great! Preserves resolution by using all of the pixels for picture.
2. Make the pixels on the top and bottom black so it looks correct when viewed in the standard mode. LETTERBOX. This makes everyone that does not have a newer TV happy. Throws away pixels to display black.
It is confusing, even when you understand the ideas.
Tom
ps 720/480 = 3/2 not 4/3 – that is because of non-square pixels, or
pixel aspect ratio.
Computers and HD have square pixels, NTSC pixels are tall, and PAL pixels are fat.
Pixel aspect ratio (par) is important to understand, but is not directly related to the anamorphic/letterbox question. The anamorphic/letterbox issue would be real, even if pixel aspect ratios were all square.
