Reflecta Cinehome screen 203 x 152 82512 User Manual

Front projections typically produce a trapezoid

distortion (keystoning). The projected picture is

larger at the top of the screen than at the bottom.

This distortion is caused by an inclined projec-

tion onto a straight hanging screen. Special key-

stone eliminators allow for an inclined positio-

ning of the screen to provide for an appropriate

means to avoid the trapezoid distortion when

using OHP. With the modern data and video pro-

jectors, the trapezoid effect can also be avoided

or reduced with the keystone eliminators.

The gain factor describes the luminance of a

fabric or a projection screen. The higher the gain,

the stronger the reflection of the screen fabric.

With an increasing gain factor, the viewing angle

of the screen decreases.

The angle of view describes the angle in degree

where the picture on the screen is still adequate-

ly visible. It is measured with reference to the

normal of the screen center. The double angle of

view (= viewing angle) thus describes the area

within which an audience should be seated.

Selecting the right screen depends on four

variables:

 

■

Rear or front projection (the latter is the most

common method).

■

Mounted firmly or portable.

■

Operated electrically or manually.

■

Depends on projection room and seating 

arrangement.

■

IIdeally, the following criteria are considered:

•

The screen width (X) should amount to at 

least half the distance between screen and 

first row of seating (D1) (example: With a 

distance of 4 metres between the first row

and screen, the minimum screen width is

2 metres).

•

The distance between screen and last row of

seating (Y) should not be larger than 6 times

the screen width (X) (example: With a screen

width of 2 metres, the last row should be at 

12 metres as a maximum).

•

The distance between floor and bottom edge

of screen (A) is 90 cm, preferably 125 cm 

for row seating.

It is determined by the projection method. The

format (also referred to as aspect ratio) is

defined by the ratio of height to width of the

screen. Depending on the projection type, the

following formats are distinguished:

•

1:1 for overhead projection (also referred

to as square)

•

4:3 for video projection (also referred to

as NTSC or video)

•

3:2 for slide projection 

•

16:9 for widescreen projection

The type of fabric is determined by the following

factors:

■

The projection method (front projection

or rear projection).

■

The projector. Each projector has a specific 

luminous efficacy (measured in ANSI lumen). 

If several projection devices are used (e.g.

beamer and OHP), it is recommended to

match the luminance (gain factor) of the

fabric to the lowest ANSI lumen value.

■

The size of the projection room. The size and 

the layout determine the seating of the

audience. The wider the seats are apart, the 

larger the recommended viewing angle of the

screen.

■

The ambient light.

The lighting conditions of the projection envi-

ronment affect the presentation quality. When the

lighting can be controlled, e.g. by darkening or a

high luminance of the projector, the "SuperLux"

fabric can be used.

The rule of thumb is: keep the ambient light

away from the screen; the brighter the ambient

light, the higher the luminance of the projector

and/or reflection of the fabric should be.

Rear projection is substantially more insensi-

tive to ambient light!

Frequent use of a screen requires an appropriate

care. All screens can be cleaned with a carefully

applied weak soapsuds. When not in use, the

screens should be retracted to their casing to

protect them against depositing dust.

Avoid to touch the screen fabric with bare

hands since, in the course of time, dust will stick

better to the (greasy) imprints than on clean

spots.

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