What is Aspect Ratio?

When we talk about 4:3 and 16:9 formats we're talking about the rectangular shape of the video image, or what is called its aspect ratio. A standard TV has an aspect ratio of 4:3. That means the picture is four units wide for every three units of height. The HDTV standard is 16:9, which is 16 units of width for every 9 units of height. So HDTV's 16:9 is horizontally wider than regular TV, which by comparison looks almost square.

Here's the problem: any given projector or TV comes in its own native format--typically either 4:3 or 16:9. On the other hand, movies and video come in many different aspect ratio formats. TV programs and videos intended for regular TV are done in 4:3 format, often denoted "1.33:1" since 4 divided by 3 = 1.33. On the other hand, programs made for HDTV are in 16:9 format, which is 1.78:1 (16 divided by 9 = 1.78).

However, these are not the only two formats that video material comes in. Movies, music videos, and other content on DVD comes in a variety of formats including 1.33, 1.78, 1.85, 2.00, 2.35, 2.4, 2.5, and so on. So there is no universal standard for the rectangular shape of a video picture. But one thing is clear: no matter which format projector you get, either 4:3 or 16:9, it will NOT fit all the video material you will want to watch in its native frame. Since there is no perfect solution, what is the right way to set up your system?

However, these are not the only two formats that video material comes in. Movies, music videos, and other content on DVD comes in a variety of formats including 1.33, 1.78, 1.85, 2.00, 2.35, 2.4, 2.5, and so on. So there is no universal standard for the rectangular shape of a video picture. But one thing is clear: no matter which format projector you get, either 4:3 or 16:9, it will NOT fit all the video material you will want to watch in its native frame. Since there is no perfect solution, what is the right way to set up your system?

Aspect Ratios: Benefits and Downsides

4:3 Theater

• Advantages: If you want to view material such as classic films, or DVD-based television series like Friends or Northern Exposure, or an IMAX special like Everest in very large dramatic format, the 4:3 set-up lets you do this in a way a 16:9 system does not. Using vertical electronic masking, one can easily block off the top and bottom of the screen when one wishes to display 16:9 or 2.35:1 material, and open the screen to it's full vertical height for the viewing of very large format 4:3 material.
• Disadvantages: Most high quality home theater projectors being marketed these days are in native 16:9. As such, it can be hard to find a 4:3 projector that delivers great video that rivals the quality of the 16:9 home theater models. And since most 4:3 projectors are in resolutions such as 800x600, 1024x768, and 1400x1050, it means that all video content will need to be scaled to fit the projector's native resolution.

16:9 Theater

• Advantages: For HDTV and widescreen DVD, 16:9 is the logical choice. All HDTV broadcast material is in 16:9, and it will be displayed in its full glory, without black bars, on a native 16:9 projector. And there is a lot of 16:9 programming available. There are many 16:9 projectors to choose from, and many of them are designed specifically for high quality home theater.
• Disadvantages: While 16:9 programming looks larger than life, 4:3 material displayed on a 16:9 projector can appear downright tiny. Generally it is centered on a 16:9 screen with black columns on each side. With broadcast 4:3 material the side columns framing the picture can be medium gray instead of black, which looks terrible. Projectors generally have some horizontal stretch options to force a 4:3 picture to fill a 16:9 frame, and if you are not concerned much about the quality of your 4:3 viewing, this can be a worthwhile compromise.

  Alternatively, if you watch a lot of movies that are wider than 16:9, you will have black bars above and below the image. A masking system can be used to close the screen's active surface area to fit the format of the movie you are viewing. This makes the picture look better, but it adds cost to your system. If you don't want to go through the trouble of purchasing and installing a masking system, you'll need to live with black bars for content that is not 16:9.

2.35:1 Theater

• Advantages: Many movies are wider than 16:9. For example, Seabiscuit, The Lord of the Rings, Dances with Wolves, Tombstone, U-571, American Beauty, and Star Wars/Phantom Menace are all 2.35:1, not 1.78:1. If many of your favorite movies are in 2.35:1, then a 2.35:1 constant image height (or CIH) setup is a good choice. This entails purchasing a 16:9 projector and using a separate, external 1.33x anamorphic lens to stretch the image out to 2.35:1 (1.78 multiplied by 1.33 is 2.35). To view 16:9 and 4:3 material, you must move the anamorphic lens out of the light path. But a set up like this can deliver the ultimate in widescreen drama.
• Disadvantages: Anamorphic lenses are not cheap, and can add thousands to the cost of your theater. Also, you must be able to move the anamorphic lens into or out of the projector's light path as you switch between 2.35 films and 16:9 or 4:3 material. Motorized mounts make this easy but add cost to the system. Cheap anamorphic lenses can impair image quality somewhat. You may also want to include an electric masking system to close the screen from the sides when 16:9 or 4:3 material is being viewed. This makes it look better, but again adds more cost to the system.