Aspect Ratio

Is the difference between the width and height of the screen viewing area expressed as a ratio – i.e. 16:10 – 16:9 – 4:3 – 2.35:1

This is usually determined by the native resolution of the projector to be used

Colour Shift

Occurs if the screen is not reflecting true colours. All colours may appear slightly more red or blue, depending on the formulation of the surface.

Frame Screen

A screen where the projection surface material is stretched under tension across a black aluminium frame. Also known as a Fixed Frame projection screen.

Front Projection

Where the screen is projected onto from the front and the light is reflected back to the audience

Gain


A measurement of the reflectivity of the screen – normal matt white front projection surface has a gain of approx. 1.1 to 1.2

Glass-beaded


A type of screen material which uses small glass beads to increase screen gain.  Trade-off is a loss of resolution and viewing angle.

HDTV Format

The aspect ratio used for HDTV and DVD. The ratio of width to height is 16:9 which can be referred to as widescreen.

Hot Spot


A very strong differentiation of centre to edge brightness of a projected image with the centre is significantly brighter than the edges

Lenticular

An optical surface on a substrate usually rear projection with the optical lens structure cast into the acrylic. Designed to enhance gain and horizontal viewing angle but may result in diminished resolution.

Maximum Viewing Distance

The distance from the screen to the furthest point from which a person will view the image comfortably approx. 6 x the viewing area height

Rear Projection

A projection system were the projector is situated behind an opaque translucent screen. Used for situations with a lot of ambient light or where a presenter needs to stand in front of the screen without disrupting the image

Roller Screen

A screen which rolls down for use and rolls up out of the way when not in use. Can be either manually or electrically operated.

Video Format
 

The ratio of width to height is 4:3 which and referred to as video for viewing images from television, laser disc, video or a data source

Data Format

The ratio of width to height is 16:10 which and referred to as data or wide computer for viewing images from laptops

Viewing Angle

The angle from which a person will be able to view the screen where the brightness is at least half as strong as when viewed directly from the front.

Viewing Distance


The distance from the screen to the point at which a person views the screen