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-
A
s
a 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
Overhead and opaque projection,
1.00:1.78 or 9:16 High Definition Television (HDTV) Anamorphic
Video
1.00:1.33 or 3:4
LCD and CRT video and data-graphics
projection
1.00:1.85
Wide Screen
1.00:2.35
CinemaScope
1.00:1.48 or 2:3
2x2 standard slides (35mm DF)
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 sssScreen
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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SCREEN SIZE SELECTION
Содержание Presentation PRO900X
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