NHTI Media Services
Glossary of Audio-Video and Multimedia Terms
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Ambient
In audio-visual, unwanted light or sound.
American National Standards Institute (ANSI)
Organization responsible for most standards used for US audio-visual and computer equipment.
Amplifier
A Device which supplies power to and strengthens an incoming signal for output.
Analog
Represented as a continuous signal or quantity, continuous, as opposed to digital; represented by discrete numbers with an extremely wide range of values.
Anamorphic
A type of lens adapter designed to produce a wide screen image from an equally condensed image on the film.
ANSI
Founded in Geneva in 1947, its membership includes more than 100 countries. An appropriate national body represents each country; for example, the U.S. member is the American National Standards Institute.
Standardization affects units of measurement, alphabetization and transliteration, and specifications for parts, materials, surfaces, processes, tools, methods of testing, and machines. The ISO publishes the results of its work as "International Standards" (IS). ISO standards are optimally reviewed every five years.
Aspect Ratio
The proportions of a projected picture area. In the US, standard video aspect ratio is 4 units wide by 3 units high, usually shown 4:3.
Audio-In
Input jack which delivers a signal to piece of equipment or a jack that receives a signal using a cable with the proper connectors.
Audio-Out
Output jack which sends an audio signal from a piece of equipment.
AutoExec.Bat
An MS-DOS file that is automatically executed when a computer is powered up. The file may contain commands to load and run other programs and the disc.
Automatic Level Control (ALC)
A circuit used in audio and video recorders to control the level of the record signal automatically to provide uniform level of the record signal without distortion due to overloading. Also called "automatic gain control."
Bandwidth
In video, the range of frequencies passed along a single channel.
Beta
A 1/2 inch video cassette format.
Bias
A direct current (DC) or a high frequency alternating current (AC) signal fed to a magnetic recording head with the audio in order to minimize distortion. AC Bias ordinarily provides higher fidelity.
BNC Connector (British Naval Connector)
A locking type if industrial connector developed by the British Navy, commonly used in professional video systems.
Boost
To raise or strengthen the signal.
Brightness
Achromatic intensity; relative lighting without regard to color.
Brightness Ratio
The difference between the brightest and darkest areas in an image. The wider the brightness ratio the wider the contrast ratio.
Broad band
A circuit which can operate over a wide range of frequencies. An example is cable TV.
Burn
Extra bright images which remain on the surface of a camera tube as a ghost image when other images are being shown.
Cable Wizard
An InFocus product; a single cord connection to plug your computer/video, audio, monitor, and mouse into an InFocus projector. The unit is Mac and PC compatible.
C-Mount
A lens mounting system for video cameras and 16mm movie cameras which accepts certain lenses.
Capacitor
A component in circuitry which stores and releases voltage within the circuit. Also a type of microphone. See also microphones.
Capstan
A rotating shaft or spindle which moves tape at a constant speed during recording or playback in tape recorders and players. A pressure roller squeezes or pinches the tape tight against the capstan to provide traction.
Cardioid
See Microphone.
Cathode Ray tube (CRT)
The video display tube used in video monitors, receivers and computer terminals. Contains a cathode and heater element at one end which produces electron beams that hit a phosphor coating on the face of the tube and make it glow or hit an oxide coating and produce voltage.
CATV
Community Access Television, mostly operated by a volunteer staff.
Ceramic Microphone
See Microphone.
CGA
Color Graphics Adapter
Character Generator
A device which displays letters and numbers electronically on a video screen for use in video productions.
Chrominance
In video, the hue and saturation of color of an object as differentiated from the brightness value or luminance of that object. Without the chrominance signal, the received video picture would be in black and white. Compare with luminance.
Cinemascope
One of the first widescreen movie formats, presenting a 2.35:1 aspect ratio with a 2:1 anamorphic squeeze.
Closed Circuit Television (CCTV)
A distribution system which limits reception of an image to those receivers or monitors that are directly connected to the origination point by coaxial cable or microwave link.
Closed Loop
A continuous loop of film or tape for repetitive playing, often in a cartridge.
Color Burst
The portion of the composite video signal which aligns the color decoder of the display device.
Color Bars
SMPTE standard test bars used to match playback with the original recording levels. Often accompanied by a 1000Hz audio tone.
Composite Video Signals
Single signals with picture and sync information.
Condenser
See Microphone.
Condenser Lens
On projectors; one or more lenses between the projection lamp and slide or film aperture to concentrate the light in the film and lens apertures.
Continuous Loop
A loop of film or tape made by splicing the ends together for continuous projection or operation.
Contrast Ratio
The ratio of the brightest possible area to the darkest possible area of an image.
Contrast
How much brighter the white areas are than the black areas.
Contrast Range
The range of grays in a video image, usually a ratio of light to dark.
Convergence
Proper alignment of the vertical and horizontal lines, as in video projection.
Coordinates
Approach, using an X axes (horizontal) and Y axis (vertical). For 3D images, a Z axis is specified.
CPU
Central Processing Unit; the portion of a computer which reads and executes programming.
CRT
Cathode Ray Tube; the display on any video or computer monitor.
Crystal
See Microphone.
CSA
Canadian Standards Association.
Cue Control
A device for rapidly advancing or rewinding a tape or film to sample the contents or find a desired section.
Curved Screen
A section of surface of a large sphere. Curved screens have viewing angles less than 180 degrees and gains greater than 1 percent.
DA
Display Adapter/Distribution Amplifier
DAT
Digital Audio Tape
dB
Decibel; a measurement of sound. See Decibel.
dBm
dB rating which indicates the number of decibels a signal is higher or lower than 1mW
DC
Direct current; maintains a steady flow and does not reverse directions (as in alternating current); usually provided by battery power.
Dead
Very sound-adsorbent.
Decibel (dB)
A relative comparison of two signal amplitudes in a manner which roughly corresponds to human sensory response to the signals. In audio work, 0 dB is the threshold of hearing and 120 dB is the threshold of pain. A change of 3 dB doubles or halves the apparent loudness.
Default
A value or parameter which is assumed, unless the user supplies an alternative. Many software programs supply default values and options.
Definition
The sharpness/resolution of a picture.
Degausser
To remove or neutralize the magnetic field of tape. On a television monitor this is a setting that can also be useful when the screen is disturbed by a magnetic field such as an unshielded speaker too close to the screen. If available, use the degauss setting and the screen resets itself.
Delete
To remove or erase a file.
Delimiter
A character which is used as a boundary or separator between two data elements.
Delta
A triangle-shaped grouping of 3 electron guns in a color CRT (Cathode Ray Tube).
Detail
Resolution or definition; the clarity of a picture
Device
Usually refers to a device such as a disc drive, display screen, terminal, printer or projector.
Diaphragm
The element in a microphone activated by sound wave vibrations. These vibrations are then converted into voltage vibrations which then produce an audio signal.
Dichroic
A type of reflector, mirror or filter which reflects and transmits different wavelengths of light selectivity, permitting a projector to provide more visible image light with less heating of the slide or film.
Digital
A system of recording data and images with discrete, noncontiguous codes; provides signal reproduction with little noise or distortion.
Digital Light Processing (DLP)
The core of the DLP system from Texas Instruments Inc., is the Digital Micromirror Device (DMD), a semiconductor light switch controlling 480,000 tiny mirrors on a single microchip. The mirrors are digitally controlled and individually activated to create very high definition, high contrast images with absolute picture uniformity and full color saturation from middle to all edges.
Digital Micromirror Device (DMD)
See Digital Light Processing above.
Digital Recording
Advanced method of recording which involves a sequence of pulses or on/off signals rather than a continuously variable of analog signal; advantages are increased frequency range and lower tape noise. May be used for control, audio and video purposes.
Digitize
The process of converting analog signals to numeric values (ones and zeros) that can be processed by computer.
Direct-Drive Image Light Amplifier (D-ILA)
A video projection technology from JVC that uses a reflective LCD to create images as a light source is reflected off the LCD and sent through the lens to the screen. (See also LCD.)
Display
Output device, for presenting legible information. Often a Cathode Ray Tube (CRT) of Liquid Crystal Display (LCD).
Dissolve
A change from one scene to another in which the outgoing and incoming visual images are superimposed or blended together for a discernible period of time as one scene fades out while the other fades in.
Dissolve Control
A device which controls the illumination from 1, 2 or more projectors in such a manner that the images fade from one to another at a fixed or variable rate.
Drop
See Screen Borders & Drop
Dropout
During playback, the instantaneous loss of a recorded signal due to imperfections in the tape.
Dual Channel
A device with two separate paths that do not interfere unless deliberately mixed. Stereo equipment is an example.
Dynamic Microphone
See Microphone.
Dynamic Range
The highest and lowest signal levels on a given device.
EGA
Enhanced Graphics Adapter
Eight Pin Connector
A jack once used for VCR-to-monitor connection. Still seen in some broadcasting today.
Electronic Viewfinder
A small picture tube (CRT) or liquid crystal display (LCD) built into a video camera and connected to the system to enable the camera operator to see exactly what is being scanned by the camera.
Electrostatic
See Microphone.
Encoder (Multi-Image Devices)
A signal generator or pulsar used with a tape recorder or other information storage device to produce the synchronizing signals or pulses for later decoding to operate combinations of devices (often Projectors) in synchronization.
Encoder (Video)
Devices that changes an individual component signals into composite signals. For example, an encoder combines y (luminance or light) and C (chrominance or color) signals to provide a video image. All video cameras contain encoders.
Equalizer
An electronic device which compensates for frequency inaccuracies in an audio or video system.
Erase Head
A separate head on an audio or video tape recorder which erases a previous signal on the tape before it is recorded on. An electromagnet which disturbs the signal previously on the tape.
Eraser, Tape, Bulk
A device that produces a strong alternating electromagnetic field which almost instantly erases an entire reel, cassette or cartridge of tape. Also called a bulk demagnetizer or degausser.
European Television
The standard television system in Europe currently has 625 scanning lines and 50 fields per second (as opposed to the NTSC system used in the US, which is 525/60).
Expansion Slots
Open connectors for the attachment of various computer peripheral devices, such as modems or monitors.
Fade
Varying the strength of a picture - either from black to full strength (fade in) or from full strength to black (fade out).
Feedback
The regeneration of sound caused by a system's microphonic pickup of output from its own speakers causing a ringing sound or signal.
Field
One half of a standard television frame, containing every other line of information. Each standard video image contains 2 fields interlaced. In the NTSC video system, a field contains 262.5 lines, a frame contains 2525 lines. There are 2 fields per frame in standard video.
Field Frequency
The number of fields per second; NTSC field frequency is 60 per second, PAL and SECAM frequencies are 50.
Filmstrip
A series of still pictures on a strip of film (usually single frame 35mm). The filmstrip may be silent or provided with an accompanying sound program. Filmstrips may be advanced manually as desired or in response to an audible beep in the audio source, or, if so equipped, automatically by a cue tone on a tape.
Filmstrip Projector
A device containing a lens system which focuses an image from a filmstrip onto a viewing screen.
Flat Screen
A flat reflecting surface with 180 degree viewing angles and gains approximately equal to 1.
Fluid Head Tripod
A tripod whose camera mount consists of two metal plates separated by a layer of fluid making movement is very smooth.
Flutter
Rapid change in frequency of an audio or video signal due to variations in tape or disc speed. A WOW is usually considered a lower frequency speed variation.
Flying Erase Head
A combination record/erase head found on video camcorders and recorders which provides cleaner edits.
Focal Length (FL)
The distance between a focal point of a lens or mirror of projection equipment and the corresponding principal plane. Shorter focal length means larger image size on the screen for given projection distance.
Focus (Automatic)
A device on slide projectors whereby after focusing the first image, remaining similarly mounted slides are automatically focused.
Focus
Sharpening a blurred image on a screen, monitor or any display; adjusting picture to achieve the greatest possible resolution.
Footcandle
The amount of light reflected by a surface one foot from a lighted candle. Metric equivalent is LUX.
Footlambert
One Lumen or one Footcandle of light over a one square foot surface.
Frame
In Video, a single image on a display created by storing a continuous sequence of scan lines. In film, action and movement are depicted by a series of still frames shown very quickly.
Frequency
The rate of repetition in cycles per second (Hertz) of musical pitch or electrical signals. Low frequencies are base; high frequencies are treble.
Frequency Response
The frequency range in audio and video systems over which signals are reproduced within a stated amplitude range. Generally expressed in dB versus Hz for example 100-5000Hz + 5 dB.
Fresnel
A flat glass of acrylic lens in which the curvature of a normal lens surface is collapsed into small steps in an almost flat plane, resulting in concentric circle forms impressed or engraved on the lens surface. Because of lower cost, less weight and compactness, it is often used for the condenser lens in overhead projectors and in studio spot and floor lights.
Front Screen Projection
An image projected on the audience side of a light-reflecting screen. See also Rear Screen.
ft/s
Feet per second
Gain or Screen Gain
The ability of a screen to amplify incident light. A matte white wall has a gain of approximately 1. Screens with gain less than 1 attenuate incident light, screens with gain more than 1 amplify incident light. For example: An image reflecting off a 10 gain screen appears 10 times brighter than it would if it reflected off a matte white wall. Curved screens usually have larger gain than flat screens. Dual purpose rear/front screens often have gains of about 0.5 in each direction. See Screen Surfaces for descriptions and gains of each type of screen surface.
Gain
The amplification of a unit of system. May be expressed in dB for electronic equipment or a factor (times) for screens.
Genlock
A device which locks the frequency of it's internal sync generator to an external source.
Geometry
The ability of a projector to accurately reproduce the border around a rectangle image.
GHz
Gigahertz; 1 billion cycles per second
Glass Beaded
See Screen Surfaces
Halogen Lamp
A projection lamp used in most low- and medium-priced models that lasts about 1,000-2,000 hours and delivers a consistent output throughout its life. Images from halogen lamps look very white compared to those from incandescent lamps but less white than those from metal halide lamps
Hardware
The electronic and mechanical components of a computer system.
HD
High Definition; often meaning HDEP and HDTV
HDEP
High Definition Electronic Production
HDTV
A high-resolution broadcast and display format commonly understood to include a widescreen 16:9 image with twice the horizontal and vertical resolution of traditional NTSC video, as well as 5.1 channels of Dolby Digital audio
Head
A small electromagnet which places magnetic signals onto a video of audio tape as it moves by; also reads those signals off a tape.
Head Demagnetizer (Degausser)
A device which provides an alternating magnetic field used during routine maintenance or remove the residual magnetism from recording or playback heads.
Headphone
A device consisting of one or two electro-acoustic receivers attached to a headband for private listening to audio sources, sometimes called an earphone.
Headset
A headphone with a built in microphone on an adjustable boom. It is audio active, meaning the wearer can both listen and respond.
Helical Scan Video Tape Recording
A type of video recording in which the video heads and the tape meet at such am angle that the resulting pattern on the tape is a long, diagonal series of tracks from the video heads, each diagonal stripe containing the full information for 1 field of video picture. Also called slant track.
Hertz (Hz)
The frequency of an alternating signal. Formerly called cycles per second.
HGA
Hercules Graphics Adapter
High Fidelity
Accurate and faithful reproduction of the original image; absence of distortion.
High Gain Screen
A projection screen employing one of several techniques designed to reflect an unusually bright image back to the audience
High Resolution
Camera, monitor or projector with a great number of scanning lines (1000-2000) which produces a very sharp, detailed image.
Homing (also Resync)
A projector feature which causes the projector to automatically return to it's starting point.
Horizontal Scan Rate
The speed in kilohertz at which the horizontal lines of the projected image are created. The higher the scan rate, the greater the resolution at a given vertical frame rate, provided that the scan rate of the video source is within the scan-rate range of the projector
Hot Spots
Bright or over exposed areas of a projected screen or image
Hub
Central part of a reel on which tape or film is wound.
Hue
Color; Value (red, green, blue, yellow) rather than intensity or brightness.
Hum
Audible disturbance caused by the power supply.
I/O
Input/Output
IC
Integrated Circuit
Image Buffer
Electronic circuitry which converts 625-line 50Hz video signals to 525-line 60Hz standards and visa versa.
Impedance
Resistance to the flow of alternating current electricity. Measured in ohms. Low impedance circuits are 600 ohms or less, and high impedance circuits may be 50K ohms or more.
Infrared (IR)
Heat rays or waves just beyond (longer than) the visible spectrum; often filtered out to reduce heat on film or slide.
Input
The program that enters a unit or system; a jack or receptacle into which a signal if fed.
Interference
Energy from an outside source which interferes with a specific signal.
Interlacing
Increasing video resolution by doubling the number of horizontal scan lines; NTSC video is interlaced.
IPS
Inches Per Second; more properly written in/s. Standard method for measuring the speed of tape movement.
Iris
A adjustable aperture in a lens made of moveable metal parts which change the diameter of the lens opening in order to control the amount of light passing through the lens. Openings are shown in f-stops.
Inverted Image
A feature enabling many video projectors to flip an image from top to bottom to compensate for mounting a projector upside down on the ceiling
Jack
Receptacle for a plug connector for the input or output circuits of an audio or video device. These are several common sizes and formats, including: Standard (1/4") phone, 0.25" or 6.35mm; Small phone, 0.206 or 5.23mm; Mini, 0.140" 0r 3.6mm; Micro or Sub-mini, 0.097" or 2.5mm.
Jack Box
A device with one plug and several jacks to permit the connection of a number of units such as headphones to one output jack. Some models are available with variable volume controls.
Keystone/Keystoning
The distortion (usually of a wide-top narrow-bottom effect) of a projected image caused by improper projector-to-screen angle.
Kilohertz (kHz)
1000 Hertz
Lag
Ghost image of an object or subject which remains on screen after the image of object is no longer on the screen.
LAN
Local area network; a computer system that allows PCs, terminal, mainframes and peripheral devices to interconnect and exchange files.
Lantern Slide
A once common slide, often glass, 31/4" x 4".
Laser
Light Amplification by Stimulated Emission of Radiation; often used in pointers.
Lavaliere Mike
A small microphone worn on a cord around the neck or clipped to the lapel. Also see microphone.
LCD
Liquid Crystal Display; liquid crystals exist in an intermediate state between liquid and solid, and realign under electrical stimulation. Exceptionally slim and light, they are ideal in computer and TV displays.
LCD Panel
An LCD device which allows text and graphics from a personal computer to be displayed onto a large screen using an overhead projector as the light source.
Learning Center
A device into which several people may plug headphones so they may all listen to the same program.
LED
Light Emitting Diode; a semiconductor diode that converts electrical energy into visible electromagnetic radiation. Often used in VCRs and other equipment displays.
Lens Speed
Refers to the ability of a lens to pass light expressed as a ratio: the focal length of the lens divided by the (effective) diameter. A fast lens which passes more light might be rated f/1.1 or 1.2; a much slower lens which passes less light might be designated f3.5. The f/number or f## = focal length/aperture.
Letter Box
A format to display widescreen films as originally intended in which the image is shrunk to fit the width of the available screen - leaving blank space on the top and bottom of the screen.
Liquid Crystal Display (LCD)
A video display process based on liquid crystals sandwiched between two polarizing transparent layers of glass. The crystals, charged by transistors, open or close to block or let light pass. In a projection format, light from an internal lamp passes through the LCD panel onto the screen. Each crystal represents one pixel.
Long Throw Lens
A lens designed for projection from a long distance, typically 50-100 feet, such as might be found in a projection booth in the rear of an auditorium.
Lumen
A measurement unit for the amount of light emitted by a projector. The higher the lumen rating, the brighter the image. Lumens per square foot are footcandles. See also LUX.
Luminance (Video)
The relative brightness values of a particular object in a scene.
LUX
The metric measurement of light quality. The measurement is taken from the reflection off the object illuminated. One Footcandle equals 10.76 LUX. A LUX equals one LUMEN per square meter.
Masking Borders
See Screen Borders and Drop
Master
Original, as in recording.
Matte White
See Screen Surfaces
Menu
The display of user options at any given point in a program
Metal Halide Lamp
A very bright projection lamp used in many medium-end and all high-end portable models that emits a lot of light relative to the power it consumes. Metal halide lamps usually last between 400-600 hours and slowly lose brightness as they age
MHz
Megahertz; millions of cycles per second.
Micro/Mini Cassette
One of several audio cassettes much smaller than the compact cassette; used principally for note taking and dictation.
Microphone
A device that converts sound into electrical signals usable by other pieces of audio equipment. Microphones vary in sound quality, generating system used, directional patterns and impedance.
Microphone Directional Patterns
OmnidirectionalMicrophone Generating Systems
- Picks up sound from all directions;Cartioid, Unidirectional
- Picks up sound primarily in the direction it is pointed, rejecting sounds from the rear of the Mic.Bidirectional
- Picks up sound in front and behind itself and rejects sounds from the side
Ceramic
- Uses a piezo-electric element to generate voltage when it is deflected by sound.Crystal
- similar to ceramic, no longer used in A-V applicationsCarbon
- Made with a diaphragm which compresses carbon granules to vary the current, no longer used in A-V applications.
Microphones dynamic
A microphone with a diaphragm connected to a fine wire coil moving a magnetic field, may be any pattern.
Condenser, Electrostatic or CapacitorMicrophonics
- A Mic with a conductive diaphragm that varies high-voltage electric field to generate a signal, may be any pattern, requires a mini amp and power supply.Electret
- Similar to electrostatic except the diaphragm is permanently charged, eliminating the need for high-voltage supply, usually requires an internal battery for a built-in pre-amp.
Audio signals (noise) caused by the mechanical vibration of elements within a system.
Mirror
A device for reflecting light; may be plane or curved. Used in projectors behind lamps to concentrate and distribute light, to reverse images for correct viewing (such as rear screen projection), and to fold light beams for more compact or more convent systems.
Monitor
A device to inspect or preview a program in both audio and video.
Multi-Standard Decoder
A device that converts HTSC, PAL, SECAM or NTSC 4.43 video to RGB video.
Muse
Multiple sub-Nyquist Sampling Encoding; one of several HDTV transmission methods; also one of the first. Some versions, including Muse-6 and Muse-9 are receiver-compatible while others are not.
NAB
National Association of Broadcasters.
Noise
In audio systems, noise is an electrical interference or any unwanted sound. In video it refers to random spurts of electrical energy or interference. Heavy noise is often called snow.
Noise-Canceling
A microphone designed to cancel ambient noise so it will not be broadcast or recorded. The housing of the microphone allows noise to reach both sides of the diaphragm simultaneously, thereby canceling each other out. A close speaking voice strikes the diaphragm on only one side so generating a stronger signal with less background or room noise. Also see microphone.
Non-Linear Optical Device
A device that converts the wave length of a laser. Theoretically, recording density using this technology could be increased by a factor of 4.
NTSC
National Television Standards Committee, which established the US standard 525-line 60-field system, often referred to as just the NTSC format. This format is color compatible. Humorously referred to as: "Never Twice the Same Color".
Objective Lens
See Projection Lens
OEM
Original Equipment Manufacturer. Companies often buy products from OEMs for sale under their own label.
Opaque Projector
Uses the principal of light reflection to create an image of any nontransparent object, such as printed pages, coins, photographs single sheets or in book form. Screen images ordinarily require a well darkened room.
Open Reel
Audio or video tape or film mounted on a reel that is not enclosed in a cartridge or cassette.
Optical Sound
Sound that is reordered by photographic means on film. The sound track is printed along the edge opposite from the sprocket holes. The sound is reproduced by projecting a narrow beam of light from an exciter lamp through the sound track
into a photoelectric cell which converts it to electrical impulses for amplification.
Output
Signal delivery from any audio or video device; also a jack, connector or circuit which feeds the signal to another piece of equipment such as a speaker or headphones.
Overhead Projector (OHP)
A device which produces an image on a screen by transmitting light through a transparency or LCD panel lying on the face or stage of the projector. The lens and mirror arrangement in an elevated housing makes it possible to project a bright image in a semi darkened room.
PAL
Phase Alternation Line (PAL) is the analog television display standard that is used in Europe and certain other parts of the world. PAL is one of the three major TV standards together with the American National Television Systems Committee (NTSC) color television system and the French Sequential Couleur avec Memoire (SECAM). NTSC is also used in Japan. SECAM is used in countries of the former Soviet Union.
PAL-M
Phase Alternate by Line; Brazilian broadcast standard which consists of 525 lines and 60 fields per second.
Peak White
The whitest portion of a picture signal.
Phone Plug
Jack or plug type most often used for microphones.
Phono Plug
Jack or plug type most often used with audio amplifiers, also known as RCA Plug.
Pixel
Picture Element; the smallest element to create an image in computer graphics; a dot.
Pixel Resolution
A measurement of resolution of a television image defined in terms of discernable pixels.
Plasma
A flat-panel display technology that uses phosphor stripes painted in ribs - one stripe per color - which are then charged to create an image on a flat surface. Most plasma displays range in size from 40-61 inches, measured diagonally
Projection Lens (Objective Lens)
A convex lens or system of lenses that recreates an enlarged image on a screen.
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Rear Screen
A translucent screen of glass or plastic with a specially formulated coating on which the image is projected through the screen for viewing. The screen is between the projector and the viewer. The image must be reversed or a mirror used to correct the image for viewing.
Reverse Image
A feature on many video projectors that enables them to flip an image horizontally. This is necessary for rear projection.
Screen Borders and Drop
Black masking borders are a black area around the edge of a projection screen. Borders enhance the perceived brightness of an image on a screen. The human eye perceives the image to have more contrast and a sharper picture with brighter colors. Borders also allow the projected image to "bleed-off" the screen for professional appearing presentations. Drop is extra fabric added to the top or bottom of the screen to adjust the screen surface to within normal viewing heights. Drop can usually be specified in either black or white.
Matte White
One of the most versatile screen surfaces and the number one choice for situations where ambient light is controllable. Its surface evenly distributes light over a wide viewing area. Colors remain bright and life-like, with no shift in hue. Screen surface may be cleaned with mild soap and water. Flame retardant and mildew resistant.
Gain - 1.1 Viewing Angle - 50 degreesGlass Beaded
A glass beaded screen surface has the ability to achieve a higher gain by reflecting more of the projected light back along the projection axis. Glass beads impregnated in the screen's surface provide additional reflectance providing a screen surface for vibrant, life-like color reproduction at moderate viewing angles. Not recommended for areas where screen will be subject to abuse or soiling.
GainGain - 2.5 Viewing Angle - 30 degrees.Video Spectra 1.5
This screen surface is especially designed for demanding video and LCD projection applications where a balance of higher gain and greater viewing angle is required. The special pearlescent surface may be cleaned with mild soap and water. Flame retardant and mildew resistant.
GainGain 1.5 Viewing Angle - 40 degrees.High Power
This screen is a technological breakthrough. The multi-layered surface provides the high reflectivity of a glass beaded surface with the unique ability to clean the surface when required. Its smooth textured surface provides the highest gain of all typed of screen surfaces with a moderate viewing angle. Can be cleaned with mild soap and water and is flame retardant and mildew resistant.
GainGain - 2.8 Viewing Angle - 30 degrees.Super Wonder-Lite
Super Wonder-Lite employs a scientifically designed ridged lenticular pattern, embossed into an aluminum vinyl and textile laminate. It's free from objectionable glare and hot spots, even in partially darkened rooms. It's washable and mildew resistant. Not available in all screen types since the material needs to be tensioned. GainGain - 2.5 Viewing Angle - 50 degrees.Lenticular
A screen surface characterized by a lens-like embosses and sliver or aluminized surface to reflect maximum light over a wide horizontal and narrow vertical angle. Must be held very flat (tensioned) to avoid "Hot Spots."
Short-Throw Lens
A projection lens designed to display the largest possible image from a short distance, such as in a rear-projection system where space behind the screen is limited
SVGA
Super video graphics array is the computer-video graphics standard with resolutions as high as 2,000 x 1,620 pixels and 24-bit color (16 million colors)
Super Wonder-Lite
See Screen surfaces
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URL
Uniform resource locator, universal resource locator, the address of a computer or a document on the Internet that consists of a communications protocol followed by a colon and two slashes
VGA
Video graphics array is the basic computer-video graphics standard, offering a resolution of 640 x 480 pixels (16 colors) or 320 x 200 pixels (256 colors)
Video Spectra 1.5
See Screen Surfaces
Viewing Angle
The widest, or maximum, angle at which viewers can clearly see an image projected onto a screen
WOW
A low rate periodic disturbance in sound usually caused by regular variations in the rotation on some mechanical component of the system. Usually WOW and Flutter are combined.
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Zebra Pattern Extremely bright sections and light sources can cause over-exposure giving poor results. With the Zebra Pattern warning on, the area in the viewfinder of a video production camera that is over-exposed, has lines on it allowing the adjustment of the electronic shutter's iris and gain to minimize the effect.
Zoom Lens
A projection lens with a variable focal length, making it possible to enlarge or shrink the image on a screen by adjusting the lens instead of moving the projector or the screen