After you decide the type of screen that will best meet your needs, it is time
to consider what aspect ratio screen you will need.
Screens are manufactured in three main aspect ratios: square, 4:3(1.333:1)
and 16:9 (1.78:1). Square screens are used primarily in business applications.
It is common to purchase large square screens and project to only a portion of
the screen, or use the one screen to project multiple images at one time.
4:3 screens are used more frequently as they match the aspect ratios of computers
and standard definition television. If you are using a 4:3 projector for home
theater purposes, it is common to use a 4:3 screen so that standard definition
material can be displayed using the complete resolution of the projector. However,
some 4:3 projectors allow their 4:3 images to be reduced in order to fit inside
of a 16:9 image, thereby allowing a 16:9 screen to be used for all types of
viewing, even if a native 4:3 projector is used.
16:9 screens are almost exclusively used for home theater and HDTV viewing. Some
electric screens will also have electric masking that can change the aspect
ratio of the image to 1.33:1, 1.85:1 and 2.35:1. One kind of screen that can
perform this function is the Da-Lite Horizon Electrol®, as seen below.