In the first two parts of this series, I discussed two critical factors to consider when choosing a screen for your home entertainment room: size and viewing distance and screen gain. In this, the third part of the series, I'll continue the discussion further, this time tackling screen aspect ratio and screen installation types.
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 a consumer video display is 16:9, which is the standard HDTV format. If you are going to use a flat panel HDTV for your home theatre, you are stuck with the 16:9 aspect ratio. However, for projection you can choose either 16:9 or the ultrawide 21:9 (also known as Cinemascope or 2.4:1 aspect ratio).
With a 16:9 screen, any movie presented in 21:9 will result in two black bars at the top and bottom of the screen, making the picture appear smaller. This is what is referred to as Constant Image Width; meaning, regardless of the aspect ratio, the width of the screen remains the same. This is NOT, however, the intention of the wider aspect ratio of 21:9. Cinemascope aspect ratio is intended to be shown WIDER than movies with 16:9 aspect ratio in order to give a sense of envelopment of every scene in the movie. With projection system, just like commercial theatres, this is achieved by using a 21:9 screen so movies, regardless of aspect ratio, will have Constant Image Height.
My personal recommendation is to choose a 21:9 screen as opposed to 16:9 aspect ratio. This is simply because from my personal movie collection of (approximately) 100 LaserDisc, 1,000 DVDs, and 1,300 Blu-ray and UHD Blu-ray, easily 90% of the movies are in 21:9 ratio. The rest is a mish-mash of 16:9 and 4:3 ratio.
Below are examples of various aspect ratios shown on a 16:9 screen in Constant Image Width and the same examples shown on a 21:9 screen in Constant Image Height.
Drop-Down, Fixed (Flat) Screen, or (Fixed) Curved Screen
If you don't have a dedicated theatre room, you may want to use a drop-down screen to de-clutter the room when you're not watching a movie. However, drop-down screens, in my experience, tend to wrinkle after a while - it can start to wrinkle anywhere from a year to five years, depending on your room's temperature and humidity changes. This results in an uneven surface, which negates the function of a screen. Wrinkle-free drop down screens use a tension system that will decrease the chance of wrinkling. But aesthetically, they tend to look ugly.
However, if you are using a short-throw projector or need to set the projector nearer to maximum zoom or use an anamorphic lens, you may need a curved screen. This is because the higher the zoom ratio (and the use of anamorphic lens) makes the distance travelled by the light from the centre point of the projector to the middle of the screen to be visibly shorter then the sides of the screen, which creates a visually distracting bowing of image and/or out of focus on the sides of the screen. This type of screen is obviously more expensive, more difficult to assemble and due to the nature of anything curved, all the viewers should be inside the width of the screen in order to view the presentation properly.
For Ultra Short Throw (UST) projectors, you can only use a dedicated UST screen. The reflection angle of the screen has been designed especially for that use. Using UST screen will increase the brightness of the projected image to its intended level. Be aware of the screen installation. All UST screens have been marked accordingly for which side should be the top of the screen and which is the bottom. Installing it upside down will result in a very dim and washed out image.
Next week, I'll conclude this series with a discussion on acoustically transparent screens and painted walls.