Choosing the Right Screen Size
Courtesy of Draper, Inc September 2003
One of the most important decisions in projection screen selection is to determine the correct size of screen based upon—
- The dimensions of the audience area.
- The projection format, or formats, to be used.
Audience Area—The goal is to make the screen large enough so those in the back row can read the subject matter easily, but not so large as to overwhelm the closest viewer.
Height—The size will vary depending on the subject matter. How detailed is it? You need a larger screen for watching the stock market ticker than for Uncle Harry's home videos. Use the following formulas for calculating screen height for maximum legibility.
- For 4:3 moving video and entertainment, screen height should be at least 1/6 the distance from the screen to the furthest seat.
- For charts and data, like those typically used in a conference or lecture room, use ¼ the distance from the screen to the furthest seat.
- For complex graphics, like those found in a command/control center, use ½ the distance from the screen to the furthest seat.
- For 16:9 HDTV projection, screen height should equal or exceed 1/3 the distance from the screen to the optimum seat (which is usually the center of the seating area).
Width—Screen width is generally determined by the height of the screen and the projection formats to be used.
Ceiling Height—In rooms with theatre seating or only one or two rows, like most home theatres, the bottom of the screen should usually be 24-36" above the floor. The bottom of the screen should be approximately 40-48" above the floor in a room with a level floor and several rows of seats. Evaluate any barriers, and try to make sure that the lower part of the screen will be visible from all seats. Extra drop may be required to position the screen at a comfortable viewing level in a room with a high ceiling.
Projection Format—Once you have determined the correct size of screen based upon the audience area, that size may be modified based upon the projection equipment. If the screen will only be used with one type of projector (NTSC video, HDTV, etc.), it is easy to determine the exact screen dimensions based upon its projection format, using formulas provided at the end of this article.
Common Projection Formats (H:W)
|Overhead, opaque projection , AV
|WideScreen, Letterbox or Panavision
|1.33:1 or 4:3
|NTSC video, most data-graphics
|1.78:1 or 16:9
|High Definition Television (HDTV)
|1.25:1 or 5:4
|High-end data graphics
Audiovisual (or AV) format screens accommodate a variety of projector types and are available in different proportions, ranging from square to wide rectangular screens that can accommodate side-by-side images. AV format screen sizes are generally described in terms of height x width.
WideScreen format (1.85:1) is suitable for letterboxed video images. This format is popular in home theatres.
NTSC video format screens, on the other hand, are specifically designed for use with video/data projectors. Their format is strictly defined as a 4:3 rectangle, and the size is usually described in terms of a nominal diagonal. Most NTSC format screens are furnished with black borders to frame the image. NTSC format screens are also suitable for use with PAL projected images (PAL is a standard television format in Europe).
HDTV format (16 wide by 9 high) is designed for high-definition television projection. The demand for HDTV screens is rising rapidly as the volume of available HDTV content grows.
Data graphics format (5:4) projectors accurately reproduce the image from a 1024 x 1280 pixel computer screen.
How to Calculate a Custom Size
Using these formulas, you can calculate a screen size to exactly fit your needs. Use the rules under "Height," above, to determine your screen height. Then find your projection format and apply the factors below to find the width and diagonal.
D = exact diagonal; H = viewing area height; W = viewing area width
|4:3 NTSC Video
|H = D x .6
W = D x .8
D = H x 1.667
D = W x 1.25
|H = D x .49
W = D x .87146
D = H x 2.04
D = W x 1.1475
|H = D x .4762
W = D x .881
D = H x 2.1
D = W x 1.135
|H = D x .3915
W = D x .92
D = H x 2.554
D = W x 1.0868
|5:4 Data Graphics
|H = D x .625
W = D x .781
D = H x 1.601
D = W x 1.281