Glossary of AV terms
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A BC D EF G HI J KL MN O PQ RS T UV W X YZ
Anamorphic Lens
An anamorphic lens is a lens that has different optical magnification
along mutually perpendicular radii.
This provides the ability to project
a source image of one aspect ratio, such as 4:3, into a different aspect
ratio, such as 16:9, by using different magnifications for the
horizontal and the vertical dimensions of the projected image.
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ANSI lumens
Brightness is measured in ANSI (American National Standards Institute) lumens: the brighter the projector, the higher the ANSI lumen rating.
The lumen rating is the average measurement achieved by recording
brightness at a number of different points within the light source. It
is the fairest and most accurate indication of a unit's overall
brightness.
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Aspect ratio
Aspect ratio is the ratio of the width of an image to its height.
The
most popular aspect ratio is 4:3 (4 by 3). Early television and computer
video formats are in a 4:3 aspect ratio, which means that the width of
the image is 4/3 times the height.
Examples: A 15 inch monitor is 12 inches wide by 9 inches high (9 x 4/3
= 12). A resolution of 640x480 is a 4:3 format (480 x 4/3 = 640). Other
formats are 5:4 used by the 1280x1024 SXGA resolution, 16:9 is used by
HDTV, and 3:2 for 35mm slides
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Brightness
The attribute of visual perception in accordance with which an area
appears to emit more or less light. (Luminance is the recommended name
for the photo-electric quantity which has also been called brightness.)
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Colour Dynamics
"The whitest whites, reddest reds, etc." High colour dynamics are a
result of dynamic range/contrast ratio's. When we describe a unit as
having excellent colour dynamics, the practical description might be
"rich colours, excellent definition, high contrast".
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Component Video
Component Video is a method of delivering quality video (RGB) in a
format that contains all the components of the original image.
These
components are referred to as luma and chroma and are defined as
Y'Pb'Pr' for analogue component and Y'Cb'Cr' for digital component.
Component video is available on some DVD players and projectors.
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Composite Video Signal
The combined picture signal, including Vertical and Horizontal
blanking and synchronizing signals.
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Contrast Ratio
The ratio between white and black.
The larger the contrast ratio the
greater the ability of a projector to show subtle colour details and
tolerate extraneous room light.
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dB
dB or decibel is a measure of the power ratio of two signals.
In
system use, a measure of the voltage ratio of two signals provided they
are measured across a common impedance.
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DCDi
Directional Correlation Deinterlacing (DCDi) was developed by
Faroudja and is a video algorithm designed to eliminate jagged edges
that are generated by interlaced video.
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Diagonal Screen
The diagonal of a screen can be computed by squaring the width,
squaring the height, adding them together and taking the square root.
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DLP
Digital Light Processing(DLP) is the commercial name for this technology from Texas Instruments (TI).
The technology inside is often referred to as either "micro-mirrors", or
DMD.
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DTV
DTV refers to the three types of digital television including
Standard Definition Television (SDTV), Enhanced Definition TV (EDTV),
and High Definition Television (HDTV).
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DVI
Digital Visual Interface(DVI).
The standard that defines the digital interface between digital devices
such as projectors and personal computers.
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Focal Length
The distance from the surface of a lens to its focal point.
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Full On/Off Contrast
Contrast is 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.
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HDMI
HDMI (High Definition Multimedia Interface) is an uncompressed,
all-digital audio/video interface that supports audio/video sources such
as a set-top box, DVD player, A/V receiver, and video.
HDMI is backward
compatiable with DVI 1.0 specification and supports HDCP.
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High Gain Screen
A screen that uses one of many methods to collect light and reflect
it back to the audience, which dramatically increase the brightness of
the image over a white wall or semi-matte screen. Technologies used
include curved screens, special metal foil screens (some polarized), and
certain glass bead screens. Prices and performance vary tremendously.
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Infra-red Remote
The traditional remote control, it transmits infra-red, 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.
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Interlaced Video
Video systems in which each frame of video consists of two video
fields.
The odd numbered lines are contained in the first field and the
even numbered lines are contained in the second field.
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Invert Image
Invert image flips the image from top to bottom, to compensate for
ceiling mounting a projector upside down.
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Keystone Correction
Keystone correction makes a projected image rectangular.
Keystone correction can be
one or two dimensional and manual or automatic depending on the
projector and the manufacturer.
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Laser Pointer
A small pen or cigar sized pointer, that contains a small battery
powered laser, which can project a small, red (typically), high
intensity beam of light that is immediately very visible on the screen.
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LCD
LCD stands for liquid crystal display and comes in many forms, sizes,
and resolutions. Its primary purpose is to present a digital image for
viewing. A common use of LCDs is as a display on a notebook computer.
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Lens Shift
The Lens Shift feature of a projector allows the optical lens to be
physically shifted up and down (Vertical) or left and right
(Horizontal).
Most lens shift mechanisms are motorized with vertical lens shift being
the most popular.
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Long Throw Lens
A lens designed for projection from the back of a room, or rather the
back of a long room.
Long throw lenses would be used in a projection
booth in the back of a theatre, etc.
A typical long throw lens might
have to be 50 to 100 FT back to project a 10FT diagonal image.
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Maximum Distance
The distance from the screen that a projector can
focus the image.
Most of the time, it is the manufacturer's opinion of how far from a
screen the projector can be to cast an image that is useable (bright
enough) in a fully darkened room.
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Maximum Image Size
The largest image a projector can throw in a darkened room.
This is
usually limited by focal range of the optics.
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Native Resolution
Native Resolution refers to the number of physical pixels in a
display device.
For example, an SVGA projector has 800 physical pixels of resolution
horizontally and 600 pixels vertically or 480,000 total pixels. This is
the native resolution of the projector.
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NTSC
The United States broadcast standard for video and broadcasting. An
older standard and lower resolution than systems used in most of the
world.
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PAL
A European and international broadcast standard for video and
broadcasting.
PAL is a higher resolution than NTSC.
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Pixel
A small coloured dot that is one of many comprising the image.
These
can just be seen when the screen is looked at very closely.
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Power/Electronic Zoom
A Zoom lens with the zoom in and out controlled by a motor, usually
adjusted from the projector's control panel and also the remote control.
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Progressive Scan
A type of display in which all the horizontal lines of an image are
displayed at one time in a single frame, unlike an interlaced scan in
which a frame consists of two separate fields with the first field
consisting of odd horizontal lines and the second field even horizontal
lines.
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Projector
A projector is a device that integrates a light source, optics
system, electronics and display(s) for the purpose of projecting an
image from a computer or video device onto a wall or screen for large
image viewing.
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QXGA
QXGA is used to define a specific display resolution.
A QXGA display has 2048
horizontal pixels and 1536 vertical pixels giving a total display
resolution of 3,145,728 individual pixels that are used to compose the
image delivered by a projector. A QXGA display has 4 times the
resolution of an XGA display.
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Rear Screen Projection
Using an opaque screen, the projector is placed behind the screen,
invisible to the audience.
It projects onto the screen and the audience
sees it on the other side.
Ideally a projector with a short throw lens is used. Since the image is projected through the screen, the image must
be reversed.
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Resolution
The amount of pixels that make up an image - e.g. 640 x 480 means 640
pixel groups across the image by 480 pixel groups down.
The larger the
number of pixels the higher the resolution and the sharper and more
detailed the image is.
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Reverse Image
Reverse image is a feature found on most projectors which flips the
image horizontally. When used in a normal forward projection environment
text, graphics, etc, are backwards. Reverse image is used for rear
projection.
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RGB
Red, Green, Blue.
Example of usage: RGB input or output often referred to as Computer
input or output.
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S-Video
A video transmission standard that uses a 4 pin mini-DIN connector to
send video information on two signal wires called luminance(brightness,
Y) and chrominance(colour, C).
S-Video is also referred to as Y/C.
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SDTV
Standard Definition Television(SDTV) refers to the 480i format.
480i is an interlaced video format that produces a full frame of 480
lines of video in two successive fields.
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SECAM
A French and international broadcast standard for video and
broadcasting.
Higher resolution than NTSC.
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Short Throw Lens
A lens designed to project the largest possible image from short
distance.
Most front room projectors use short throw lens. They are often required
for rear projection, where the depth behind the screen is limited.
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SVGA
SVGA is used to define a specific display resolution.
Resolution is defined by the number of individual pixels that a display uses to create
an image.
An SVGA display has 800
horizontal pixels and 600 vertical pixels giving a total display
resolution of 480,000 individual pixels that are used to compose the
image delivered by a projector.
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SXGA
SXGA is used to define a specific display resolution.
Resolution is defined by the number of individual pixels that a display uses to create
an image.
An SXGA display has 1280
horizontal pixels and 1024 vertical pixels giving a total display
resolution of 1,310,720 individual pixels that are used to compose the
image delivered by a projector.
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UXGA
UXGA is used to define a specific display resolution.
Resolution is
defined by the number of individual pixels that a display uses to create
an image.
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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VGA
VGA is used to define a specific display resolution. Resolution is
defined by the number of individual pixels that a display uses to create
an image.
A VGA display has 640 horizontal
pixels and 480 vertical pixels giving a total display resolution of
307,200 individual pixels that are used to compose the image delivered
by a projector.
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WiFi
Wi-Fi is Wireless Fidelity and is based on the IEEE 802.11
specifications for wireless local area networks (WLAN).
WiFi was developed by a
working group of the Institute of Electrical and Electronics Engineers
(IEEE).
There are four specifications: 802.11, 802.11a, 802.11b, and 802.11g.
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WSXGA
WSXGA defines a class of SXGA displays with a width resolution
sufficient to create an aspect ratio of 16:9.
Resolution is defined by
the number of individual pixels that a display uses to create an image.
A WSXGA display has 1920 to 1600
horizontal pixels and 1080 to 900 vertical pixels respectively that are
used to compose the image delivered by the projector.
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WXGA
WXGA defines a class of XGA displays with a width resolution
sufficient to create an aspect ratio of 16:9.
Resolution is defined by
the number of individual pixels that a display uses to create an image.
A WXGA display has 1366 to 1280 horizontal
pixels and 768 to 720 vertical pixels respectively that are used to
compose the image delivered by the projector.
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XGA
XGA is used to define a specific display resolution. Resolution is
defined by the number of individual pixels that a display uses to create
an image.
An XGA display has 1020
horizontal pixels and 768 vertical pixels giving a total display
resolution of 783,360 individual pixels that are used to compose the
image delivered by a projector.
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Zoom Lens
A lens with a variable focal length providing the ability 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.
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Zoom Lens Ratio
Is the ratio between the smallest and largest image a lens can
project from a fixed distance. For example, a 1.4:1 zoom lens ratio
means that a 10 foot image without zoom would be a 14 foot image with
full zoom. Conversely, a 10 foot diagonal image at 15 feet with no zoom
would still be a 10 foot image at 21 feet at maximum zoom (15 x 1.4 = 21
feet). A zoom lens is "not as bright" as a fixed lens, and the higher
the ratio, the less light output.
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