Why are HBO movies in letterbox format instead of filling the screen?

[WAGGGG]

It just seems like a lot of screen size is being wasted.

[ThatDonGuy]

Because a movie screen has a width to height ratio of 1.85:1,  while a TV screen has a ratio of about 1.78:1.

There are three options: show the black bars, cut off the sides of the film, or stretch the film's picture vertically (but if you do that, the images are stretched).

[andyross · Accepted solution]

Many movies are in 2.35:1, leaving very large letterboxing. 1.85:1 will leave small bars. Some older movies from the early widescreen years (50's) are even wider.