Glossary of Terms - U

A glossary of terms covering lighting, audio, vision and staging in the event and theatrical industry.

There can be a number of meanings for some terms which can vary from country to country and manufacturer to manufacturer. Information within this guide is indicative and every situation can require a different approach and solution. All care has been taken, however, Image Group NZ accepts no responsibility for inaccuracies. If you have any suggestions, comments or queries regarding this list please contact us.


Short wavelength source of light at the end of the visible light electromagnetic spectrum which causes specially treated materials to fluoresce on an otherwise blackened stage. Used for special effect and for lighting onstage technical areas (eg Fly Floors). Ultraviolet sources designed for stage use are known as Black Light sources and have all harmful radiations filtered out.

A single conductor cable with a surrounding shield that connects to ground. Such a system is called unbalanced because it cannot be balanced or offer common mode rejection.

An input in which one of the two terminals is at ground potential or connected to the chassis ground.

This term commonly refers to microphones which pickup sounds predominately from one direction as opposed to all directions (omnidirectional). Unidirectional microphone types include cardioid, super-cardioid and hyper-cardioid. Unidirectional microphones are most often used in sound reinforcement applications because they are generally less prone to feedback than omnidirectional types.

Comparison of the brightness of one area to an adjacent area. In general, the brightest part of the image will normally be in the centre area. When moving out to the edges, the intensity of image will vary in a non-linear function. This means that one corner of the screen will not be the same brightness as another corner of the screen. A typical projector specification may call for up to a 30% difference between the centre area and the corners.

Light from below the actors - from a light source on the stage floor. French: contre-plongÚe


    The part of the stage furthest from the audience.
    When an actor moves upstage of another and causes the victim to turn away from the audience he is "upstaging". Also, an actor drawing attention to himself away from the main action (by moving around, or over-reacting to onstage events) is upstaging.

UXGA is used to define a specific display resolution. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. A UXGA display has 1600 horizontal pixels and 1200 vertical pixels giving a total display resolution of 1,920,000 individual pixels that are used to compose the image delivered by a projector.


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