Screen Size Selection

Overhead and opaque projection,

High Definition Television (HDTV) Anamorphic Video

LCD and CRT video and data-graphics projection

Wide Screen

CinemaScope

2x2 standard slides (35mm DF)

Courtesy of Draper Shade & Screen

One of the most important decisions in screen selection is to determine the correct size of screen based upon-

1.The dimensions of the audience area.

2.The projection format, or formats, to be used.

In some situations, these two questions yield the same answer; in others they do not and compromises must be made. Here are the key considerations:

Audience Area-In determining the correct size of screen in rela- tion to the audience area, the goal is to make the size large enough so those in the rear of the audience area can see the sub- ject matter easily, but not so large that those in the front of the audience area have difficulty seeing the full width of the project- ed image.

Width-The generally accepted guideline in determining the screen width is the Two and Six Rule:

A. Screen width should equal the distance from the screen to the first row of seats, divided by two.

B. Screen width should equal the distance from the screen to the last row of seats, divided by six.

In case of a difference between these two guidelines, the one yielding the larger size should prevail.

Height-Asa rule of thumb, the screen height should equal or exceeding the distance from the screen to the last row of seats, divided by eight. Ceiling height and projection format considera- tions may modify this standard.

Ceiling Height-The bottom of the screen should be approximately 48” above the floor to allow all members of the audience to see the bottom of the projected image.

Projection Format-Once you have determined the correct size of the screen based upon the audience area, that size may be based upon the type, or types, of projection equipment to be used. If the screen will only be used with one type of projector of (over- head projector, CRT video projector, etc.), it is easy to determine the exact screen dimensions based upon the projection format of that projector. Projection formats are expressed in terms of aspect ratio, which is the relationship of the height of the projected image to its width. Aspect ratios of common projection formats are listed below.

If it is necessary to modify the screen dimensions based upon the formats of projectors to be used, it is preferable to hold the screen height constant and increase the screen width as neces- sary, rather than to hold the width constant and decrease the height.

ASPECT RATIOS OF COMMON PROJECTION FORMATS H:W

1.00:1.00 1.00:1.78 or 9:16

1.00:1.33 or 3:4

1.00:1.85

1.00:2.35 1.00:1.48 or 2:3

Note - Vertical presentation of a slide reverses its aspect ratio. To allow this, use a 1.00: 1.00 aspect ratio for any type slide.

Projection Formats

Most models of DRAPER screens are offered in both audio visual and 3:4 video formats. Certain models are also offered in HDTV and WideScreen formats. The differences between these formats are stated below.

We are glad to provide any DRAPER screen in the size and projec- tion format of your choice. We can provide any size up to and including the largest published size. If you do not find the size and format you need listed, please call or fax your requirement to us, and we will be delighted to quote.

Audiovisual (or AV) format screens are intended for general use. They accommodate a variety of projector types and range from square to wide horizontal in aspect ratio.

AV format screens are described in terms of height x width, and are standardly furnished without black borders, although borders are optionally available.

Video format screens, on the other hand, are specifically designed for use with video projectors. Their format is strictly defined as a 3:4 rectangle, and the size is usually described in terms of a nominal diagonal. Conventional models of video format screens are standardly furnished with black borders to frame the image on all four sides, allowing for video projector overscan. Tab Tensioned electric screens are routinely furnished with black bor- ders at the sides and bottom, although black masking at the top is optionally available.

HDTV format (9 high by 16 wide) is also available for high-defi- nition television projection, Anamorphic Video and Wide Screen format (1: 1.85).

How to Calculate a Custom Size

Draper also manufactures custom size screens to meet your speci- fication. Virtually any size within the maximum shown for a given model is available. Please call for pricing on special sizes. If you need to calculate a custom size, these formulas may be useful (D = exact diagonal; H viewing area height; W = viewing area width):

3:4 Video:

H = D x.6

W = D x.8

D = H x 1.667,

D = W x 1.25

9:16 HDTV:

H = D x.49

W = D x.87146

D = H x 2.04

D = W x 1.1475

1:1.85 wide screen:

H = D x.4762,

W = D x.881,

D = H x 2.1,

D = W x 1.135

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