Glossary
Glossary of Terms

Listed below is a list of terms used in media, whether video, audio, projection and other multimedia items.  The list is not exhaustive but will help you understand the media industry and components a little better.

A

Ambient Light

Any light in the viewing room created by a source other than the projector or screen.

Aspect Ratio

The ratio of height to width of a frame or screen. In a 4:3 aspect ratio, the width of the image is 4/3 times the height. Most current TV and computer video formats are in a 4:3 aspect ratio. A 15 inch monitor is 12 inches wide by 9 inches high (9*4/3 = 12). A resolution of 640x480 is a 4:3 format (480*4/3 = 640). SXGA is a 5:4 aspect ratio is (1280x1024), HDTV is 16:9 for that movie theater feel, and 35mm slides are 3:2.

ANSI Lumens

ANSI stands for American National Standards Institute. It is a standard for measuring light output. Different lamps play a role on light output. Halogen lamps appear dimmer than another metal-halide, even if the two units have the same ANSI lumen rating. Type of LCD technology (active matrix TFT, Poly-Si, passive), type of overall technology (LCD vs. DLP vs. CRT), contrast ratios, among other factors can also affect the end result.

Aliasing

Jagged edges along the outer edge of objects or text. Anti-aliasing refers to software adjustments that correct this effect. This effect is created by inadequate sampling techniques in computer-produced images.


Backlit

A remote control, projector control panel, or other object illuminated from behind. This can be helpful when working in darkened rooms.

Bandwidth

The frequency range of a particular transmission method. In video systems, this value is expressed in MHz, and the better the signal, the greater the bandwidth required.

Bit Mapped Graphics

The type of graphic that is defined and addressed on a bit-by-bit basis which makes all points on the screen display directly accessible.

BNC

Bayonet Neill Concelman (after inventors Paul Neill & Carl Concelman). Used with coaxial cables, this connector receives all R, G, B, H-Sync and V-Sync information, and composite video.

Build Slide

"Build series" slides show audiences where a topic is heading a line at a time. Each new line added appears in a bright color while previous the line drops back to a darker color.

Button

A graphic element inside an interface that represents an embedded action or function.


Color Temperature

A method of measuring the "whiteness" of a light source. Metal halide lamps produce higher temperatures than halogen or incandescent lights.

Clip-Art

Graphics that have been previously published which can be imported into a presentation simply by copying and pasting.

Color Resolution

The total number of colors available, expressed in bits per pixel.

Compatible

When different hardware or software can be used together without a major over-haul.

Contrast Ratio

The ratio between white and black. The larger the contrast ratio the greater the ability of a projector to show subtle color details and tolerate extraneous room light. There are two methods used by the projection industry: 1) Full On/Off contrast measures the ratio of the light output of an all white image (full on) and the light output of an all black (full off) image. 2) ANSI contrast is measured with a pattern of 16 alternating black and white rectangles. The average light output from the white rectangles is divided by the average light output of the black rectangles to determine the ANSI contrast ratio. When comparing the contrast ratio of projectors make sure you are comparing the same type of contrast. Full On/Off contrast will always be a larger number than ANSI contrast for the same projector.


D

Diagonal Screen

One corner of a screen to the opposite corner. A 9FT high, 12FT wide, screen has a diagonal of 15FT. If the screen is 12x12, it would still rate 15FT diagonal since that would be the diagonal usable.

Desktop Videoconferencing

Videoconferencing via personal computer.

Digital Light Processing (DLP)

Developed by Texas Instruments, DLP is a light processing system that utilized hundreds of thousands of tiny spinning mirrors to reflect images. Many feel it is the most accurate reproduction of color and images available today.

Dot Pitch

The distance between the dots on a CRT display. The closer together the dots are create a higher resolution of a displayed image.

Dithering

Making digital images appear smoother by adding color or random noise during the digitization process.


E

EGA

AKA Enhanced Graphics Array, EGA is an image which displays 640 pixels by 350 lines with 16 colors from a palette of 64 colors.


F

Front Room Projector or Position

A unit that sits close to the screen, its short throw lens projects an image size that is about the same as the distance to the screen. 6FT diag. screen = 6FT distance. Generally the unit might be as close as 3/4 the screen size or as far as 1.2 times image size.

Front Room Projector or Position

A projection unit that sits close to the screen, thereby requiring a shorter throw-distance.

Flat Screen

A CRT made more flat than a standard tube by using more than one electron gun. Beneficial to people who require concise reproduction and great detail such as graphic designers.

Focal Length

Focal length is the distance between the lens and its focal point. A smaller focal length indicates a wider-angle lens.


G

Genlock

Synchronizing signals between two video sources, which is necessary when overlaying computer graphics on an image from VCR, camera, or videodisc player.

Ghosting

A shadow or weak secondary image as seen on a monitor or display which is created by multiple path broadcast transmission errors.


H

High Gain Screen

A screen that uses one of more methods to collect light and reflect it back to the viewing audience, which will increase the brightness of the image over a white-wall or semi-matte screen.

H Sync

AKA Horizontal synchronization. A marker, which indicates to a computer or video signal that it, is the beginning of a line.

HDTV

AKA High Definition Television. High definition, wide-screen television broadcasting with digital audio.

Horizontal Frequency

AKA kHz, the total number of horizontal lines scanned per second in a displayed image.

Horizontal Resolution

The total number of vertical lines individually perceived across the horizontal rows of a monitor.

Hz

AKA Hertz. A measure of frequency in cycles per second. Used to express the frequency of an electrical signal or event.


I

Invert Image

Many projectors that are ceiling mounted are mounted upside down. Invert image corrects the image digitally so your projected image is not also upside down.

Interlacing

Technique used to reduce flicker caused when the first created video field fades while the next is being written.


J

JPEG

AKA Joint Photographic Experts Group. An international group, which is working, on a proposed universal standard for the digital compression and decompression of still images used in computer systems. The JPEG idea reduces image size as much as 65:1 and still maintains image integrity by getting rid of subtle color differences the human eye can not see.


K

Keystone Correction

A projectors ability to correct the effects of "pointing up" or "pointing down" at a screen enabling the projector user’s audience to view a rectangular image rather than one with a wider top or bottom.

Keystoning

The distortion (usually a wide-top narrow-bottom effect) of a projected image caused by a projector "pointing up" or "pointing down" at its screen. Named after its similarity in shape to the keystone used in constructing an arch.


L

LCD

AKA liquid crystal display. This technology comes in many forms, sizes, and resolutions. Its primary purpose is to present a digital image for viewing. They are used in many notebook computer displays and also used as technology inside a projector to project high-resolution digital images.

Laser Pointer

A hand held device that emits a thin laser beam that focuses a bright dot (usually red) on projected images or just about anywhere. Used by presenters to direct the viewer's eye to a particular point of interest.

Lenticular

A screen surface that has an embossed geometric shaped pattern that affects view/angle performance and reflection of ambient light.

Long Throw Lens

A lens designed for projection from the back of a room. Long throw lenses would be used a projection booth in the back of a theater, or from the back of a large classroom. A long throw lens would have to be 50 to 100 FT back to project a 10FT diagonal image.

Projector Lenses

ChurchProjectors.com offers long-throw, short throw, standard, and zoom lenses to fit your special projection needs. Custom lenses will work with select projectors to help you create the right size image with maxium inpact in your church, auditorium, or home theater space. If you have questions about projector lenses call us today.


M

Metal Halide Lamp

The type of lamp used in most high-end portable projectors. These lamps output a very "hot" temperature light, similar to lamps used in streetlights. Metal Halide whites are super white (with a hint of blue) and make Halogen lamp white very yellowish by comparison.

Multimedia Presentations

The integration of text, art, graphics, photography, animation, audio, and video into presentations.

Multiplexing

The condensing of many signals into a few or one signal that still represents all of them. An LCD panel performs the de-multiplex function. It takes video signals that contain whole frames of video data and displays them as individual signals on each pixel.


N

NTSC

The USAA's broadcast standard for video and broadcasting. It is actually a lower resolution than systems used in most of the world. However, by the year 2002 stations will be required to broadcast higher resolution video signals.

Network

Allows two or more computers to exchange information quickly and easily.


O

Output

Material that a computer generates from its memory for display on a monitor or for transfer to other media, such as paper or magnetic storage such as zip or floppy disks or a CD-ROM.

Overlay

The capability to superimpose computer-generated graphics and/or text on motion or still video.

Overhead Projector (OHP)

An OHP is designed to project images from transparencies onto a screen.


P

PAL

AKA Phase Alternation by Line. The standard color system used throughout Western Europe, except in France.

Poly-Si (silicon) LCD

A popular LCD technology for the top of the line LCD projectors, which results in increased color saturation, with contrast ratios above 200:1.

Pixel

Short for picture element. The smallest element in a displayed image. A color pixel is a combination of red, green and blue subpixels. Total pixels are usually expressed in horizontal x vertical dimensions (e.g. 640 x 480).

Power Zoom

A zoom lens with the zoom in and out controlled by a motor, usually adjusted from the control panel or a remote control. This is as compared to Digital zoom, which does this same function Digitally.

Presentation Ergonomics

The study and science of optimizing relationships between a presenter and the presentation environment.

Projection Axis

Direction of the "imaginary" line that extends from the center of the projection lens through the center of the screen.


R

RGB

Red, Green, Blue; the type of monitor generally used with computers. RGB input or output often referred to as Computer input or output.

RCA connector

The connector used with VCRs and stereos for composite video signals and audio.

Real Time

The transfer of data that returns results so quickly that the process appears to be instantaneous.

Rear Projection

Projecting an image through a translucent screen material for viewing from the opposite side. This method of projection is also an option for home theater use in large spaces.

Remote Mouse and Keyboard Control

Allows presenter complete control of computer presentation without direct access to projector. Allows for freedom of movement.

Resolution

Number of pixels (or dots) per unit of area, measure in number of pixels wide by the number of pixels high that can be displayed on the screen or monitor. More pixels per unit of area produce a higher resolution.

RS-232C

A cable that connects a computer and its peripherals.


S

SaBRE

AKA Subtractive Bi-Refringent Effect, a technology that allows two panels rather than three to generate the full 16 color VGA palette. The top panel provides white, magenta, blue, and cyan; the second brings colors from white through yellow and to red.

SECAM

The French broadcast standard (used in some other international markets) for video and broadcasting. Like PAL, SECAM is also a higher resolution than that of the US, until 2002.

Simulated color

Also known as "false color," or "colorized." Projected colors that are not the same as the original image. Some products use a single, colorized LCD, often with purple for dark shades and yellow for light shades (purple background/yellow foreground). Therefore, what should appear on a screen as blue may be yellow, green may be purple.

SVGA

AKA Super VGA. Refers to a computer signal that is higher than the standard VGA resolution of 640 pixels by 480 lines with 16 or 256 colors. SVGA graphics cards may output resolutions such as 1024 x 768, 1280 x 1024, 1600 x 1200 pixels or higher, with 16.7 million colors displayed.


T

TFT

AKA Thin Film Transistor. A technology used to make Active Matrix LCD panels wherein each pixel has its own transistor switch.

Throw Distance

Length of the projection beam required for a projector to produce and image of a desired size.

TSTN

AKA Triple Super Twist Neumatic. A technology used to make Active Matrix LCD panels wherein each pixel has its own transistor switch.


U

UXGA

Resolution of a computer generated image. A UXGA projector will be able to display a 1600x1200 image from a computer running in a UXGA video mode. If the computer is not running in a UXGA video mode, typically the projector will resize the image to 1600 x 1200.


V

VGA Resolution

VGA Resolution normally refers to a 640 x 480 pixel display, regardless of the number of colors available. Originally VGA was 640 x 480 16 colors.

V-Sync

AKA Vertical synchronization. A marker in a video signal for the beginning of a frame.

Varifocal Lens

A projector lens that has three focal elements contained in a single assembly.

Vertical Resolution

The total number of horizontal lines that can be perceived in the vertical direction of the screen.

VGA

AKA Video Graphics Array. This is the standard interface for the IBM PS/2. It is the only analog graphics card IBM has used (other cards handle digital information) 720 x 400 in the text mode, graphics mode 640 x 480 resolution.

Video Compatibility

Ability of computers and projection units to transmit and receive data to read and/or project various video tape standards such as NTSC, PAL, SECAM and S-VHS.


W

Whiteboard

Document-conferencing product that lets multiple users simultaneously view and make notes on a document with pens, highlighters and drawing tools.


X

XGA

Acronym for Extended Graphics Adapter. A standard introduced by IBM that includes VGA as well as resolutions up to 1024 pixels by 768 interlaced lines.


Y

Y/C Connector

A 4-pin DIN connector used for high-end S-video sources.

Y-Cable

A cable that splits the monitor signal so that it will work simultaneously with both a monitor and a LCD panel.


Z

Zoom Lens

A lens with a variable focal length. This translates to being able to adjust the size of the image on a screen by adjusting the zoom lens, instead of having to move the projector closer or further.