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Glossary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A
Aspect Ratio
Aspect ratio relates to the shape of an image, how square or oblong is the shape, it is the ratio of the width of an image to its height. Most projectors that are designed for home cinema use will have a ratio known as 16:9 for every 16 points across the width there are 9 in height. This is the standard widescreen aspect ratio and will give you the best possible image for your movies.
Older tv’s and projectors had a standard aspect ratio of 4:3. Modern widescreen tv’s are usually 16:9
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B
BNC
Short for Bayonet Neill Concelman connector. This is a type of connector that is used for component video connections and is an alternative to the more common RCA type connectors. This type of connector is usually found on more expensive projectors.
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C
Calibration
Calibration is carried out on projectors to ensure that the image delivered meets a standard format. With projectors this is usually the D65 colour standard.
Component video
Component video is a method of delivering a video signal in high quality format. There are both analogue and digital formats available (Y’Pb’Pr’ being analogue and Y’Cb’Cr’ being digital). Component video is better than both S-Video and composite video for quality. The reason it is better is because it splits the video signal into it’s base components thus ensuring that there is now interference from other parts of the signal.
Composite video
Composite video is a method of delivering a video signal. It is probably the lowest quality video connection available and if you are spending a lot of money on a projector you will probably not be interested in this. Composite video connections consist of three connections being audio left, audio right and video.
Colour wheel
See DLP
Contrast ratio
Contrast ratio 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 handle rooms that have additional light sources as well as the projector. There are two methods for measuring the contrast ratio Full On/Off (measures the ratio of the light output of an all white image and the light output of an all black image), and ANSI contrast (measures contrast between black and white alternating rectangles). Most projector manufacturers use Full On/Off as it is a higher ratio than the ANSI standard.
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D
D65 Colour Standard
An industry standard that represents a known point on a greyscale. Projectors and TV’s are calibrated to D65 to give a true as possible representation of an image.
DB
dB or decibel, is a measurement invented by Graham Alexander Bell one of it’s uses to record a measurement against noise level. The higher the decibels the higher the noise output from a device. For example noise output from a car horn near you would be 110 decibels. A quiet whisper would be 20 decibels.
DLP
Digital Light Processing is a technology developed by Texas Instruments that is based on a digital micromirror device (DMD), this is a computer chip with millions of microscopic, hinged mirrors. The chip is no larger than the average thumbnail and contains some 480,000+ mirrors.
Red, green and blue light is filtered through a colour wheel that spins at high speed and directed at the DMD witch switches the mirrors to reflect the light or not. The reflected light is directed through a lens and onto a screen, creating the image. High end projectors use three DMDs and have no need for the colour wheel. Each of the DMD corresponds to a separate colour red green and blue.
DVD
Digital Versatile Disc or Digital Video Disc. DVD is an optical disk technology similar to the CD-ROM. A standard DVD holds a minimum of 4.7GB of data. This is enough for a full-length movie. DVD is now the standard format used for movies in the consumer marketplace.
DVI
Digital Visual Interface. DVI is a standard that defines the digital interface between digital devices such as projectors and personal computers. For devices that support DVI, a digital to digital connection can be made that eliminates the conversion to signals to analog giving a pure and true image
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E
EDTV
EDTV stands for extended definition television and is a class of digital television (DTV) that refers to the 480p format. 480p is a class of definition the higher the number the better the definition.
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H
HDCP
High-bandwidth Digital Content Protection is a system for protecting copyrighted digital content that uses the DVI (Digital Visual Interface) or HDMI (High-Definition Multimedia Interface). It does this by encrypting its transmission between the video source such as a set-top box, DVD player, or computer and the digital display device such as a projector, monitor or television. To view digital HDCP protected content, both the sending and receiving device must support HDCP.
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 monitors such as a digital projector or digital television DTV.
HDTV
High Definition Television. This is the highest-resolution subset of Digital Television and offers film like picture quality with impressive surround sound. HDTV has a widescreen aspect ratio of 16:9.
High Definition
High definition in projectors relates to the quality of the image the higher the resolution (number of lines that make up the width and the number of lines that make up the height), the better the image quality. Projectors tend to use 1024 * 576, 854 * 480 and 1280 * 720. a resolution of 1280 * 720 would normally be found on more expensive projectors and is a High Definition image.
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L
Lamp life
This relates to the bulb (lamp) that is used to project an image and is measured in hours. Basically the more hours the better as lamps are not cheap to replace. If you watched two hours a night on your projector with an a lamp life of 3,000 hours it would last around 4 years. By this time you may be looking at getting a new projector anyway.
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. Before DLP most projectors were LCD. LCD is not as good for projecting movies and is better suited to corporate presentations.
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). This allows for adjustment of the projected image.
Lumens
Is a measurement of the flow of light (Brightness). As a rule of thumb the higher the number the brighter the image. This can be useful when using a projector in a room that has a light source other than the projector (table lamp etc.)
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M
Mode
This relates to the various set ups that a projector can support whilst still producing an image that is acceptable. The common ones are front (Projecting forwards onto a screen),rear (Projecting from behind the screen) and ceiling (The projector can be mounted on a ceiling using a special bracket. Celing mounted projection can usually be front or rear)
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P
PLASMA
Plasma is a flat screen technology that is similar to LCD. It has become very popular as a TV standard as it allows you to locate your screen anywhere including the wall. The image quality is not as good as a projector.
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R
RGB
Abbreviation for red, green and blue signals, the primary colors of light – and used within DLP projectors
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S
S-Video
S-Video is a standard that allows the connection of devices and produces a video signal that is better quality than a composite connection, but not as good as a component connection. The change in signal quality is quite noticeable between composite and S-Video.
SCART RGB
An audio/video connector commonly used in Europe. The SCART connector's 21 pins carry two audio in and out channels, video in and out channels and RGB signals. The SCART cable is often used as an alternative to Component connections.
Screen trigger
Projectors that support screen triggers will allow you to connect to an automatic motorized screen. So the screen is lowered and raised automatically without you needing to touch it. A real ‘bells and whistles’ feature.
SMPTE
Society of Motion Picture and Television Engineers is a professional engineering society who develop technical standards for motion pictures and television.
Surround sound
Generic term to describe a sound system with speakers both in front of and behind the audience. A good surround sound system can make a huge difference to your movie experience.
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V
VGA
VGA 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 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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W
Widescreen
Term used to refer to 16:9 screen ratio. Projectors designed for the home cinema market will usually have this as their standard or native aspect ratio.
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