Aspect ratio

It has been suggested that Aspect Ratio be merged into this article or section. (Discuss)

Aspect ratio is the ratio of the width of an image to its height.

The two most common aspect ratios heard mentioned are 4:3 (1.33:1, or traditional TV) and 16:9 (1.77:1, "widescreen" TV). Film releases are usually somewhere between 1.85:1 and 2.35:1, with Cinerama coming in at 3:1 or wider.

When working with aspect ratios and television, it's important to remember that there are more than one of them involved: the AR of the original program, that of the broadcast, and that of your set.

Discussion

With a few rare exceptions, most programs produced originally for television are created in either 4:3 or 16:9 format. How that master tape is aired on a network, however, may vary. For example, The West Wing is mastered in 16:9 and broadcast that way on NBC-HD, but on the standard definition network, the show is broadcast in letterbox format: the 16:9 image is vertically centered between a pair of black bars.

If you're watching the SD channel on an SD television set, you'll get it in letter box. If you're watching the HD channel on a widescreen set, you'll get the picture full-screen, the way the director intended.

It's when you combine the two that problems crop up.

Most widescreen sets have an Aspect control, and different sets can do different mappings from non-HD signals to the wide screen (and most have different names for each, of course):

• Normal: places the 4:3 picture horizontally centered on the screen between 2 vertical black bars.

• Full: linearly stretches the 4:3 picture horizontally to fill the entire 16:9 screen. Unless the original signal was a squeezed 16:9 original (as from a recent camcorder), this is almost certainly the wrong choice for normal television viewing, since it makes everyone look fat (this is the source of my term "Fat-Head Syndrome", and yet it's the most common setting among 'civilians'. It's even seen quite a bit on sales floors, where the people really ought to be expected to know better. It's just that people seem to *really* hate seeing those black bars on the sides. (Some sets have multiple tuners, or inputs, and can stack 3 additional 4:3 pictures on one side to fill the space.)

• Stretch: this mode, not found on all sets (some Mitsubishis are known to have it) stretches only the last 1/5 of the picture on each side, non-linearly, to fill the sidebars, leaving the center of the picture unstretched. This is actually a better compromise in practice than you might expect.

• Zoom: This mode uses the 4:3 picture to fill the screen horizontally (all other modes fille it vertically), and sooms in on the center stripe of the picture. It clips about 5% of most broadcast letter boxed pictures at the top and bottom, but is a reasonable choice for watching letterboxed SD broadcasts on a 16:9 set.

These modes all apply to what happens when the set it presented with a 4:3 program signal; in general, most widescreen sets presented with an HD signal merely display it to fill the screen.