Part 1 of a two part series about aspect ratio. First, we’ll talk 4:3 and 16:9. What is the difference? What do those aspect ratios look like? Then, in Part 2, we’ll talk anamorphic aspect ratio and how aspect ratio affects captions and subtitles.
You’ve probably heard about aspect ratio before, even if that is not the term that was used. Who knows, you might even have been in an argument about widescreen versus pan and scan.
Aspect ratio is a number that describes how wide an image is compared to how tall the image is. It describes the shape of the image.
First, a little terminology clarification because it can get a little complicated…
1. 4:3 and 16:9 (occasionally 4×3 and 16×9) are the common notations and values for aspect ratio.
2. The ratio can also be expressed as a decimal rather than with a colon: 4:3 = 1.33, because 4 divided by 3 is approx 1.33.
3. Note that the size of an NTSC picture is generally said to be 720×480, which isn’t precisely 1.33. That’s because it’s measuring lines instead of square pixels, and we really don’t want to get into pixel aspect ratio yet. (Yikes!)
4:3 (Regular NTSC TV)
This is the aspect ratio you’re thinking of when you imagine an iconic TV, the square with the rounded corners. The image is almost as tall as it is wide. Until a few years ago, all American television looked like this.
Now most TV is produced in 16:9. If you watch a widescreen TV show on an old-school TV, it will either be letterboxed (see below) or the sides will be cut off. This depends on the settings on your TV or receiver and also what flags the broadcaster is transmitting. Most networks require that programs delivered in 16:9 HD respect 4:3 title safe, so text is in the center of the frame and not cut off for people using standard sets.
Letterboxed 4:3 (…or “I hate those black bars”)
Letterboxed video is still 4:3. The video itself is not actually widescreen. Lots of people get this wrong; even some software gets it wrong. Letterboxing is a way to simulate a widescreen picture on a 4:3 monitor. The actual active video is presented as a widescreen rectangle, and the rest of the space is filled up with black mattes on the top and bottom. But the overall image itself is still 4:3.
The mattes do not (we repeat do not) cover up any of the picture. You can confidently assure your grandma that the black bars are not stealing any television from her. Seriously, some people do get really upset about letterboxing, but not letterboxing is what takes picture away. When you buy a “full screen” DVD of a movie, if they still sell those, there won’t be any black bars, but the sides of the picture will be cut off (see the first image in this article) in order to make the rectangle into a square. Beautiful scenery and even whole characters can be excised this way. These zoom-and-cropped, pan-and-scan full-frame releases aren’t nearly as common as they used to be, but you’ll still see them from time to time.
16:9 (Widescreen)
This is a rectangle. If you have a TV that is a rectangle, congratulations, you will see the entire widescreen picture in full screen. A 4:3 picture will be either pillarboxed (see below) or stretched out in freaky ways. We can’t even tell you how many big fancy plasma TVs we’ve seen that have had their settings all wrong, including the aspect ratio. The tears, the sadness, the gnashing of teeth!
It is possible to have a 16:9 widescreen video that also has letterboxing—it means that the active picture is ultra-widescreen, like 2.35:1, and is being fit into a 16:9 aspect ratio. That isn’t usually relevant to standard definition, though; it generally happens when a very wide film is being shown on 16:9 HDTV.
Just because an image is 16:9 does not mean it is high definition. Standard definition video can also be 16:9, almost always anamorphic…
Pillarboxed 16:9
Pillarboxed video is when a 4:3 video displayed on a 16:9 screen. In order to display the video in its correct proportions, black bars are added to along the side of the frame. Pillarboxing will be used instead of displaying a stretched video. And just like a letterboxed video, the black mattes do not cover up any of the picture.
Whew, got all that? Any questions? In Part 2 we’ll discuss anamorphic video and how aspect ratio affects captions and subtitles.