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Definitions for the Audio Visual field.

F through M

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Focal Length

A fundamental measure of lens performance, usually expressed in millimeters.

Frame

A single complete picture in a film recording or video.

Frame Grab

Electronically capturing and storing one screen of information.

Front Projection

Projecting onto a reflective surface of an opaque screen material for viewing from the same side, as opposed to rear projection.

Full frame

Generally refers to as filling a computer monitor with a video clip. Using the entire screen.

Full frame, 30 frames per second (fps)

Running full video frames on a computer at 30 frames per second, providing the same seamless video as movies, video tape and TV.

Gradation

The slow change of a colors density; a change in tone or texture, etc., between adjacent areas of an abject or the corresponding image.

Hard wired remote

A remote control that has a connecting cable to the device it controls. Often used at a podium or lectern.

HDTV

High Definition Television, a term used to describe advanced production and delivery systems.

High Gain Screen

A screen that uses one of many methods to collect light and reflect it back to the audience. This results in an image which is considerably brighter than the image on a white wall or matte screen. The disadvantage of a high gain screen is often a narrower viewing angle. High Gain screens are more expensive than Matte screens, but attention to the screen can make a big difference, particularly in "tough" environments such as trade shows.

Hz, (KHz, MHz)

Hertz or (Kilohertz or Megahertz). Cycles per second. (Kilo = 1,000, Mega = 1 million). These terms are used to express the frequency of an electrical signal.

Image Compression (Compressed)

Compresses higher resolution images into lower, for example compressing a SVGA (800 x 600) down to VGA (640 x 480).

Infra-red remote

The traditional remote control, it transmits infrared light, like a television remote. Typical range is limited to 30 or 35 feet. Infra-red requires line of site or a bounce off of a hard surface. These signal from this type of remote control cannot pass through walls.

Integrated Services Digital Network (ISDN)

Standard digital service capability that includes one or more circuit-switched communication channels capable of carrying digital voice, data, or image signals, a packet-switched channel for out-of-band signaling and control, plus a collection of standard and optional features that support information productivity for the user providing higher-speed Internet access than analog systems.

Interactive

Employing the active participation of the user in determining the flow of the multimedia program.

Interface

To connect normally incompatible components so that the signal from one is readable by the second.

Interlacing

A technique used for the display of live video and some computer graphics whereby the image is displayed in horizontally stacked lines known as fields.

International Power Supply

A device that can operate under a variety of power requirements. Some units are "self-switching", they will automatically switch to whatever power source you plug it into. Others will have to be switched (internally or externally) to accommodate a different voltage or cycle range.

Invert Image

Electronically flips the image from top to bottom, to compensate for ceiling mounting a projector upside down, as most projectors have "keystone" correction built in to compensate for the distortion created by "pointing up" from the table to the screen. The image must be inverted when the projector is hung upside down from the ceiling. Most projectors are operated with the lens about even with the bottom of the screen in a "table top position", or even with the top of the screen when ceiling mounted.

IR (Infra-Red)

A type of wireless transmission using infrared light waves.

IR communication standard

A standard for wireless communicating with peripherals (printers wireless keyboards, pointing devices) and a computer. This feature is becoming common on laptop computers.

Joystick

A device used to control movement of an pointer icon (cursor) across an image. Each physical location of the "stick" corresponds to a location on the screen.

Keystone

The "wedge" shape picture caused when the projector is not even with the horizontal or vertical center of the middle of the screen. Most data and video projectors use optical and electronic methods to eliminate this problem.

Laptop
A small portable computer with a self contained LCD display.

Laser Pointer
A small pen or cigar sized device that contains a small battery powered laser, which can project a small, red, high intensity spot of light that is immediately very visible on the screen.

LCD
Liquid Crystal Display - a glass panel display that works by controlling the opacity of segments of itself by varying the electrical signal. Each individual segment called a pixel, acts as a shutter, to control the amount of light being passed through.

LCD Projector
A projector using an LCD to modulate the light.

LCD Projection Panel
The predecessor to today's self contained projectors. They lack their own light source, and instead, sit on top of a overhead projector. Although panels are light (5-8LB.), even on specially designed, extremely bright, overhead projectors, their image is not as bright as today's self-contained projectors. Therefore use is limited to darkened rooms on small screens.

Light Valve
Another projection technology, found in the "big" systems, these units are extremely bright and capable of producing "stadium size" images.

Long Throw Lens
A lens designed for projection from a very long distance. Long throw lenses would be used in a projection booth in the back of a theater, etc. A typical long throw lens might have to be 50 to 100 ft. back to project a 10 ft. diagonal image.

Luminance
The relative brightness values of a particular object in a scene.

Lux
A unit for measuring light, as methods of measurement are not standardized, numbers provided by manufacturers usually do not provide all necessary information to compare one product to another. A preferred unit of measuring light output is the ANSI Lumen.

Maximum Distance
The longest distance from the screen that a projector can properly focus the image.

Maximum Image Size
The largest image a projector can throw in a darkened room.

Megabyte
1 million, or 1,048,576, bytes or characters. It is abbreviated as MB or Meg.

Memory
The device in the computers main unit that stores information, both permanently (hard-disk) or temporarily in microchips (RAM or random-access memory).

Menu Driven
Refers to the type of controls on a projector. The user will be offered an on screen menu display of major categories such as Computer, Video, Audio, Display, Options. After selecting one, you will get another menu of choices with items like brightness, contrast, etc. after select one of these nd you can then adjust it. Most projectors are menu driven but also offer the most widely used functions in a non-menu fashion, such as separate control buttons for volume, brightness, and contrast, as well as switching between sources.

Metal Halide Lamp
The type of lamp used in many medium and all high-end portable projectors. These lamps emit a very high amount of light for the amount of power they consume. Unlike many other types of lamp, they slowly lose intensity (brightness) as they are used. As they get older the corners of the projected image becomes noticeably darker. Metal halide lamps usually last between 400 and 600 hundred hours. They usually cost from $300 to $600 retail, but most are around $500. These lamps output a very "hot" temperature light, Their whites are "extremely" white and make Halogen lamps whites look yellowish in comparison.

Micro-Mirror Technology (DLP)
see Digital Light Processing (DLP)

Microprocessor
An electronic circuit, usually on a single microchip, that performs arithmetic, logic, and control operations, customarily with the help of internal memory, also on the chip.

Minimum Distance
The closest position that a projector can focus an image onto a screen.

Minimum Image Size
The smallest image a projector can create.

Multimedia
A vague expression that indicates the ability to integrate several different types of media. Media types include, video, photos, sound, clip art, graphic design, text and more.

Multimedia Computer
Generally refers to a computer that has a minimum set of features including, active matrix display, a sound card and speakers, fast video, and usually a CD-ROM or DVD player built in.

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