At first glance the idea of a super widescreen 2.4 format has a lot of appeal. And if you tend to watch mostly films in 2.4 format, it is a great alternative. However it has one big problem: In most home theater rooms, a 2.4 aspect ratio screen is the smallest screen you can install. Your 16:9 and 4:3 images will be much smaller than they would be if you used a 16:9 screen. Why? In the vast majority of home theater situations, the room dimensions place a practical limit on the maximum width of the screen before placing any limitation on its height.
Let's assume for example that the wall you are projecting onto is 14 feet wide and 9 feet high. Let's also assume you want to leave two feet to either side of the screen for speaker placement and aesthetic clearance from the side walls. Practically speaking, these room dimensions limit you to a maximum screen width of about 10 feet.
Now, since this room has a 9 foot ceiling, the height of your screen can be pretty much anything you want. If you go with a 2.4 screen, it will be 10 feet wide and 4.25 feet high. If you opt for a 16:9 screen, it will be 10 feet wide and 5.62 feet high. (In theory, if you were installing a classic movie theater for the screening of pre-1953 films, you could install a 4:3 screen that is 10 feet wide and 7.5 feet tall.) The point is that the room's dimensions limit the width of the screen much more than they limit the height. Believe it or not, in most home theater spaces, the 2.4 format actually turns out to be the smallest screen you can install from a total square footage perspective.
Now, on a 10-foot wide 2.4 format screen, every image you project will be the same height, which is 4.25 feet. That's why 2.4 set-ups are often called Constant Image Height, or CIH for short. The only thing that varies is the width of the image. A film in 2.4 will take up the entire 10 foot screen width, but a 1.78 image will be only 7.56 feet wide. The total square footage of that 1.78 image will be 4.25 x 7.56 = 32.1 sq. ft. Conversely, if you installed a 16:9 screen that was 10 feet wide, the total square footage of your 1.78 image would be 10 x 5.62, or 56.2 square feet. Hmmm...roughly 32 vs. 56 square feet. That is a much bigger 1.78 image--almost double the square footage.
Let's look at a graphic illustration of this. The following are pictures of two 10-foot wide screens. The first is 2.4 format, and the second is 16:9. As you can see, the 16:9 picture is larger since it gives you more vertical space to deal with. The following images are of the 1.85 format scene from Chicago. On a 2.4 screen, it is displayed in pillar-boxed format, and on the 16:9 screen it is virtually full frame:
So despite the fact that the two screens are identical in width, a 1.85 movie like Chicago looks much bigger on the 16:9 screen--almost double the size--due to its increased vertical height.
Meanwhile, regardless of whether you use a 10-foot wide 2.4 or 16:9 screen, a 2.4 film will be the same size on either screen--10 feet wide and 4.25 feet tall for a total of 42.5 square feet no matter what. The only difference is that the 2.4 screen gives you a full frame effect, and the 16:9 screen gives you black bars top and bottom.
Therefore, to recap: if you are like most people, your room will determine the maximum width of your screen. Once you establish how wide a screen you can install, that determines the absolute size of your 2.4 image. The only remaining question is how big do you want your 1.78 and 1.85 material to appear? If you want those images to be smaller than your 2.4 films, go with a 2.4 screen. If you want them to be larger than your 2.4 films, increase the screen's vertical height and go with the 16:9 format.
In this article I've used an example of a room with a wall 14 feet wide and 9 feet high to illustrate the concept. Your room will probably be different, so it is important to study your room's particular limitations and come up with your own assessment of what will work best for you.
And always keep in mind, your ultimate decision should be based on the type of material you prefer to watch. I have a viewing room that has a 10.5 foot wide 2.4 screen, and it is fine for 2.4 movies. But it is not so exciting for HD music concerts. When I put on the Eagles Farewell 1 Tour, I want that enveloping, sitting-in-the-front-row experience, and the 1.85 image on my 2.4 screen is too small to create that effect. For parties I like to put music concerts on the screen, and I want the image to have maximum impact. So I remove the 2.4 screen and replace it with a 16:9 screen that is not quite as wide, but overall has about 50% greater square footage for 1.85 material. The larger image has a much more commanding presence...a more riveting WOW factor.
The question is...what kinds of content do you care about most in your theater? If your interests are primarily in 2.4 movies and you prefer to see 1.78 and 1.85 in a smaller size, the 2.4 screen is an excellent choice. If you add HD sports broadcasts and music concerts to your viewing mix, you will usually get a more immersive experience with a 16:9 screen.
Aspect ratios and the projector you select
We have concentrated here on the aesthetic considerations of how you want images to be screened in your theater. But the selection of a 16:9 vs. a 2.4 screen has an impact on the projector you ultimately select. Almost all home theater projectors throw a native 16:9 image, so any home theater projector is easily matched to a 16:9 screen. However, when it comes to 2.4 format screens, you will need to do one of two things to match the projector with the screen: (1) select a projector with a zoom lens that exceeds 1.3x in zoom range, preferably with powered zoom and lens shift, or (2) plan on installing an external anamorphic lens along with your projector. This second option is much more expensive. We will get into these issues in a later article, but for now it is worth keeping in mind that if you go with a 2.4 screen you will need a projection system that can project various types of material in constant height format.
The bottom line is this: you are the director in your home theater. You can decide how you want various format images to be screened. Some people love the visual effect of the super wide 2.4, and would prefer to limit the size of 16:9 and 4:3 material in order to make the 2.4 films look larger in comparison. Some prefer to take advantage of a taller screen that allows a larger square footage presentation of 1.78 and 1.85 images. There is nothing right or wrong with either approach. But no matter what you do, a compromise will be made. No single screen format is perfect for all types of video/film material.
This article has focused entirely on the first, and most important, decision you must make in setting up a home theater--what aspect ratio is best for your personal tastes and viewing preferences? After deciding this, the next questions are how big should your screen be, and how far should you sit from it? Continue to the next article in this series, "Choosing the Right Screen Size.