Building Your Own Home Theater
The first and most important decision you can make about your new home theater is this:
What is aspect ratio, you ask? Aspect ratio is the ratio of the width of the screen to the height of the screen. Essentially, it describes the shape of the rectangle. Today the most popular aspect ratio for consumer video display is 16:9, which is the standard HDTV format. The numbers mean that the picture is 16 units wide for every 9 units in height.
Sometimes you will see the 16:9 aspect ratio referred to as 1.78:1, or simply 1.78. Why? Because 16 divided by 9 = 1.78. But it means the same thing. A 1.78 screen is 1.78 units in width for every unit of height.
If you are going to use a flatscreen HDTV for your home theater, you are stuck with the 16:9 format for better or for worse. Though they come in a wide variety of sizes, they are all 16:9 aspect ratio. But if you are planning to use a projector and screen, you have another option, which is 2.4:1, commonly known as the Cinemascope format. This is a wider format than standard 16:9. Many people prefer it because it matches the aspect ratio of a lot of movies being produced today.
Think about the black bars
Here is a simple fact of life: Videos and movies are made in a variety of different aspect ratios. There is no standard. So no matter what aspect ratio your screen is, you will always end up with black bars at the top and bottom of some material, and black pillars at the sides of other material. The only time you don't get black bars is if you are viewing video or film shot in the format of the screen you are using--either a film done in 1.78 displayed on a 16:9 screen, or a movie shot in 2.4 on a 2.4 Cinemascope screen. In both of those cases, the screen frame will match the picture precisely, and no black bars will exist.
(By the way, we're assuming you want to see the material you watch in its correct original aspect ratio, as the director created it. If you don't, there are several ways to stretch, manipulate, or crop video images to get them to fill a 16:9 screen and eliminate the black bars.)
So in choosing between a screen aspect ratio of 1.78 vs. 2.4, you are really deciding how the various film and video formats will appear on your screen. For example, if you select a 16:9 screen, all of your 2.4 format movies will have black bars top and bottom. If you select a 2.4 screen, all of your 16:9 material will be "pillar-boxed" in the center of the screen with black columns on each side.
So 16:9 must be best for HDTV broadcast, and 2.4 Cinemascope must be best for movies, right?
Well, not so fast. Many people assume that all modern films are being done in the super widescreen 2.4 format. They aren't. A few, including some new and popular titles, are done in plain ol' 16:9 (1.78). As examples, here are some movies that are either done in 1.78, or have been modified to 1.78 for Blu-ray...
But beyond some films and all of the HDTV broadcast programming that are done in 1.78, many live music concerts on Blu-ray are in 1.78. Once you get into 1080p home theater, many people like to experience music concerts in HD on the big screen. Some of the concerts on Blu-ray that are done in 1.78 include...
Roy Orbison, Black & White Night
And in addition to 1.78, there is 1.85
Another format that is very close in aspect ratio to 1.78 is 1.85. This format has been popular for a long time, so there is a huge library of 1.85 films on the market. Examples of movies done in 1.85 include....
Saving Private Ryan
Not only are there scores of movies on Blu-ray in 1.85, but live music concerts appear in this format as well. A few examples include...
Eagles Farewell 1 Tour
So, the bottom line is that when planning your home theater, it is a good idea to anticipate you will be viewing a reasonable amount of video and film content in either 1.78 or 1.85, as well as the wider 2.4 format.
How do you fit 1.85 movies on a 1.78 screen?
There are two ways to watch 1.85 material on a 1.78 screen. The first option is to set the projector's lens so it just fills the 1.78 screen with a 1.78 image. When it is set this way, all 1.85 movies will be shown with very tiny black bars at the top and bottom. On a 120" diagonal screen, the black bars would be about one inch each at the top and bottom. Many people think this is no problem, so they set it up this way so that 1.78 material fits the frame perfectly.
The alternative is to set the projector's lens so that a 1.85 movie fills the screen vertically. When you do this, you cause the picture to overshoot the screen surface. Those tiny black bars fall onto the screen's frame top and bottom, which is good, but you lose a bit of the picture on the sides. Meanwhile, 1.78 material overshoots the screen surface on all four sides. But if you can live with the small amount of edge cropping, you end up with all 1.78 and 1.85 material filling the screen with no black bars. You lose about 2% of the image on the sides for 1.85 material, and 2% on all four sides for 1.78. In situations were you must see the 1.78 image 100% full frame, you can adjust the projector's zoom lens to reduce the image to get it entirely onto the screen. For many people this is an acceptable compromise.
As a side note, if you like the idea of living with minor edge cropping to get rid of the tiny 1.85 black bars, a better alternative would be to have your screen cut to 1.85 instead of 1.78. When you do this, all 1.85 films will fit perfectly without those tiny black bars. Meanwhile, material in 1.78 will slightly overshoot the top and bottom edges of the screen, but will remain fully visible on the sides. On a 120" diagonal screen, about one inch of the top and bottom of the 1.78 image would fall onto the frame, which is less than 2% of the image on both edges--not much of a sacrifice. On occasions where you absolutely must see the entire 1.78 image, the projector's zoom can be adjusted slightly to reduce the image size, resulting in small black columns on each side. But this set up eliminates both black bars and image cropping on 1.85, and limits cropping on 1.78 to just the top and bottom, rather than all four edges.
Which of these options is the better choice depends on what you watch most frequently. If you watch a lot of HDTV broadcast content, you will probably want to see it full frame. Assuming the tiny black bars on 1.85 are not a concern, the 1.78 format screen will be the best choice. If you don't watch much TV, and your primary objective is seeing 1.85 movies full frame without edge compromises, then the 1.85 format screen is the better choice, at least between these two very similar formats.
Okay then, what about the 2.4 films?
Obviously, most films today are done in the wider format 2.4 Cinemascope. Part Two of this article will focus on the display of 2.4 movies, and the selection of the 2.4 format screen as an alternative to conventional 16:9.
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