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Anamorphic Widescreen
Refers to the stretching or squeezing of an image so that it utilizes the entire area of a film frame with a different aspect ratio. The most common usage has a 1.85 to 1 or greater wide screen movie "squished" on film with 4:3 aspect ratio frames. A special lens is used on the projector to exactly reverse this distortion and produce the correctly proportioned picture on the screen. "Anamorphic" in video is a misnomer. Video has no aspect ratio until it is displayed on the screen. The TV set or monitor determines the aspect ratio using settings specified by the viewer or sometimes automatically by taking some format data (not the picture data) from the video signal. So far the label "anamorphic" is used only for the DVD 16:9 enhanced wide screen programs or 16:9 high-resolution programs.
Ansi Lumens
A standard for measuring light output, used for comparing projectors. Unfortunately, there are enough variables that the eye will often disagree radically with the ANSI rating. At best, ANSI lumens do fairly well comparing "apples" to "apples". If however one projector uses Halogen lamps and another metal-halide, the halogen projector will seem noticeably dimmer even if the two units rate the same. Other variables, including type of LCD technology (active matrix TFT, Poly-Si, passive), type of overall technology (LCD vs.DLP vs. CRT), contrast ratios, etc. all effect the end result.
Aspect Ratio
Plainly and simply, the aspect ratio describes the relationship between the width and height of televisions. Widescreen TVs have a ratio of 16:9 and you will often see the set described by the ratio rather than by being called widescreen. TVs with this ratio have a screen that is 1.7 times wider than it is high. The standard TV, the one that we lived with for years before the birth of the widescreen TV, has an aspect ratio of 4:3. Most 16:9 TVs have a zoom facility that enables you to watch films and TV programmes broadcast in 4:3 format without having the black bars down the side of the screen. The popularity of widescreen can be seen in the fact that quite a lot of films on terrestrial TV are now broadcast in widescreen, and there are even specialist widescreen movie channels available on satellite. Virtually all movies are filmed in some kind of widescreen ratio, enabling film directors to shoot stunning scenes and amazing panoramic views.
A/V Inputs
Refers to the jacks and connections on a specific piece of equipment used to connect multiple sources to a specific piece of equipment. The more inputs you have, the more options you have to upgrade your kit in the future.
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 analog component and Y Cb Cr for digital component. Component video is available on some DVD players and projectors.
Composite Video
Refers to a video signal where both the luminance component and the colour component(s) are transmitted on a single wire or broadcast in a limited bandwidth. Each of the major systems NTSC, PAL, and SECAM has its own definition of how the luminance and colour are combined. The luminance and colour information must be separated before the picture can be displayed. It is well worth investing in a better connection such as RGB SCART or S-Video.
CRT (Cathode Ray Tube)
Electronic vacuum tube in which a thin beam of electrons is shot through the space inside and against the far wall (faceplate; screen) or a plate inside. This includes all picture tubes used in TV sets or computer monitors.
CRT Projector
Generally much more expensive than the LCD projector, the Cathode Ray Tube projector has linear doublers that double the scanning rate of TV pictures, in turn enhancing the picture quality. A CRT projector produces a higher quality picture than an LCD one, but is trickier to install and set up.
De-Interlacer
Device or circuit to convert interlaced video to progressive scan video with the same number of scan lines per full video frame. Loosely referred to as a line doubler. Although "outputting each scan line twice" will produce reasonable progressive scan video, "de-interlacer" should refer to devices with more sophistication to interpolate intervening scan lines or fetch scan lines from the previous and/or next field for a better quality picture.
Digital TV
A digitised TV signal is one that is compressed in size by reducing repeated information in order that several TV channels can occupy the space of one analogue channel. The days of traditional analogue television are numbered as the Government has announced it will be switched off as early as 2008. Current estimates suggest that this is not realistic as the take up of digital TV has not been as fast as expected.
Direct View
This is the standard type of TV we have been used to, where the CRT projects the image directly on to the glass. For people on a modest budget this is a good option, but always go for the flattest screen possible.
DLP (Digital Light Processing)
The commercial name for this technology from Texas Instruments (TI): The technology inside is often referred to as either "micro-mirrors", or DMD: It works this way: build a few hundred thousand tiny mirrors, and line them up in 800 rows of 600 mirrors each. Now attach a hinge to each of those 480,000 mirrors. Attach each of those 480,000 hinges to its own very tiny motor. Power each motor with electrostatic energy. The motors tilt their mirrors up to 20 degrees at incredible speeds. This allows the mirrors to modulate light from a lamp, and send the "modulated signal" out through a lens, on to a screen. The most amazing part of DLP micro mirrors, is the scale of size. The 480,000 mirrors (actually 580,000 are used), hinges and motors are packed onto a "wafer" a bit larger than your thumbnail.
Flatscreen TV
We always recommend a flatscreen TV. They may cost a bit more but reflections on the screen are cut down and your picture is displayed, as it would be on a cinema screen rather than being wrapped round a curved monitor.
Interlace
The drawing of all of the odd lines, then all of the even lines, to display each video frame. Every once in a while a TV set has the defect (line pairing) of having the even lines not land exactly between the odd lines, which results in loss of vertical resolution.
Keystone Correction
Most decent projectors come with this feature. Keystone correction allows you to change the shape of the image projected. Basically, if the projector is not set straight or what you are projecting onto is at an angle, you can adjust the keystone to make the image seem flat and normal.
LCD (Liquid Crystal Display)
A panel on which tiny spots become transparent or opaque in response to electronic signals and which, given enough of such spots arranged in a pixel grid, can be used as a video display or in a video projector.
LCD Projector
LCD projectors (Liquid Crystal Display) are usually the most popular with home cinema enthusiasts. The reasons behind this are because they are often bright, light and easy to set up. It is literally a case of plugging in and away you go. They also offer multimedia options.
Line Doublers
A set of circuits whose purpose is to paint each scan line on the picture tube twice (three times, four times) and thus fill in the gaps between scan lines. A device (with circuits inside) which converts interlaced video to progressive scan video is also referred to as a line doubler. It too delivers output that has twice as many scan lines per second as its input and it may also use the technique equivalent to painting each scan line twice. This is one of the main reasons as to why a lot of people swear by the CRT projector for home cinema use.
MPEG (Moving Pictures Experts Group)
An organization, or more correctly a large enough collection of groups that could be called an institution, which among other things developed various data encoding and compressing schemes so an full length movie could be recorded on a five inch disk (a DVD).
NTSC
U.S. government and industry committee that defined the 525-line 60 (59.94) interlaced fields per second analog broadcast TV standard over 50 years ago. (This format is referred to as NTSC.) Of the 525 scan lines, 480 (give or take a few) contain the picture and the rest contain synchronizing information, hold the encoded closed caption text, and provide a time delay to move the electron beam back to the top of the screen. NTSC is used mainly in North America and Japan. Originally 30 frames per second, the standard was changed slightly to 29.97 frames per second at the time colour was introduced since that change made it easier to incorporate the colour information into what is now a composite video signal. The change was so small that practically all older TV sets continued to receive the signal properly without loss of vertical hold. If a TV or DVD player has NTSC playback, it will be able to relay signals from VHS tapes and discs from these countries.
PAL
A 625 line 50 interlaced fields per second analog broadcast standard used in many parts of the world but not the U.S.A. So named because the chroma is phase reversed on every other scan line to reduce picture artefacts. (NTSC is that way also.) Programs are not interchangeable with NTSC even though they may occupy the same broadcast channels or be recorded on videocassettes of the same size and shape. Pal stands for Phase Alternating Line and this is the television format that is used in the UK and Europe.
Pan and Scan, or P&S
Term used to describe a wide screen movie committed to video with a lesser aspect ratio. The picture is zoomed in on so that more or all of the TV screen is filled (to satisfy popular demand and improve vertical resolution), but both sides of the original picture obviously do not fit. A video technician "pans" the conversion machine (e.g. telecine) back and forth to capture what he considers or what he was told is the most important part of each scene while cropping the sides. Even film to film copies, notably 16mm and 8mm prints, have been made using the pan and scan technique.
Pixel, or Pel
Picture element; the smallest spot on the screen that can be resolved as having a different brightness or colour from what is next to it. The "number of pixels vertically" is equal to the number of scan lines; for example if you block off all but a narrow vertical stripe on the screen, you will see a series of dots, one per scan line. For a computer screen or digital video, the screen is divided into several hundred "grid positions" horizontally as well; a pixel must be exactly one of the grid positions, not half of one and half of the next. For analog TV pictures, we can say that the number of pixels horizontally is equal to the maximum number of alternating black and white dots that can be reproduced all the way across the screen, which equals the aspect ratio times the number of lines of resolution horizontally.
Plasma Screens
Plasma screens have two plates with about O.1 mm between them. Tiny cells are contained within this gap and these are coated with red, green or blue phosphors. Plasma is trapped between the plates and voltages are then passed over the different cells to trigger a colour reaction. Because of this, the ultra-thin screens can display an astonishing 16.8 million different colours. Expensive, but high quality.
QXGA
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.
RGB
A video signal transmitted as three components using three wires and which are the respective colour content of red, green, and blue, respectively. R, G, B -- The red, green, and blue components referred to separately. RGBHV -- The RGB signal where horizontal and vertical synchronization (sub)signals are carried on fourth and fifth wires, respectively. RGBS -- The RGB signal where horizontal and vertical sync. are combined (composite sync.) and carried on a fourth wire. RGsB -- The RGB signal with sync. combined with the green signal so that just three wires are needed. (There is no such thing as sync. on blue or sync. on red.)
S-Video
A video signal transmitted as two components requiring two separate wires: luminance (technically referred to as Y) and colour (C). Although commonly found in S-VHS VCRs, this signal is not limited to such VCRs. Unfortunately, it does not carry audio and, because of this, you will need to use another connector or separate amplifier to hear what is going on.
SCART Socket
This European standard 21-pin plug and socket is used to link up home entertainment equipment.
SVGA
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.
SXGA
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.
Throw
The term used to describe the ratio between the distance of the projector lens to the screen and the size of the image. The size of the room dictates what sort of projector you buy, and if you have a small room you will need a projector that can produce large images over a short distance.
UXGA
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.
VGA
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.
Wide Screen
Refers to a video program whose picture has a wider aspect ratio than 4:3.
WSXGA
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.
WXGA
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.
XGA
An XGA display has 1024 horizontal pixels and 768 vertical pixels giving a total display resolution of 786,432 individual pixels that are used to compose the image delivered by a projector. |
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