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Glossary
of terms |
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| For your convenience, this glossary defines
projector-related terms with which you may not be familiar. |
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Resolution |
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The number
of pixels - measured in number of pixels wide by the number
of pixels high - that can be displayed on the screen.
The higher the number of pixels, the higher the resolution.
VGA (640 x 480)
SVGA (800 x 600)
XGA (1024 x 768)
SXGA (1280 x 1024) |
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Contrast ratio |
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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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Aspect ratio |
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The ratio
of height to width of a frame or screen. Most current
TV and computer video formats are in a 4:3 aspect ratio.
Most cinema and DVD movie formats are in a 16:9 aspect
ratio. |
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Projection screen size
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The size of
the projected image as measured diagonally across the
image.
A : Projection screen size
B : Production distance |
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Projection distance |
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The distance
that the image can be projected and clearly displayed
(in focus). |
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Throw ratio |
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Throw ratio
= projection distance/projected image width.Also expressed
as 50" @ 2 m which means from a distance of 2 m the
projected screen size will be 50 inches.
Throw ratio = B / A |
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Keystone correction |
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A projector's
ability to correct the effects of "pointing up"
or "pointing down" at a screen enabling the
audience to view a rectangular image rather than one with
a wider top or bottom. |
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Rear and ceiling projection |
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The projector's
ability to provide 180-degree rotation of the projected
image, and flip the projected image, to enable the projector
to project the image from a variety of installation locations. |
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Response time |
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The time needed
for a pixel to turn on and off. Response time is a measure
of how long a display takes to change the image. Fast
response time is superior for playing computer games and
viewing action movies and sports. |
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PIP (Picture-in-Picture) |
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This feature
allows for more than one input source to be displayed
on the screen simultaneously. |
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Loop-through |
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A loop-through
allows another device, often a monitor, to be connected
to your projector. A connected monitor lets you view the
projected image without having to turn your back to your
audience to face the screen. |
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Brightness |
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| ANSI Lumens is a standard scale to measure
the overall brightness value for projectors. The measurement
represents the average value of nine points on the projected
screen image. |
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Displayable colours |
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The total number of colours available expressed as a number
of colours or bits per pixel. Typically the number of colours
is 16,777,216 or "24-bit" colour. The number of
discrete colours available in the RGB spectrum is 256 x 256
x 256 (each RGB value has 256 levels) = 16,777,216.
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Projection lens |
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| In general, the projection lens is specified
using aperture, focal length and zoom ratio. A larger aperture
provides better brightness. A shorter focal length provides
a better throw ratio and a larger zoom ratio enables larger
projected screen size over a specific projection distance. |
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Lamp life |
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| The lamp life means the guaranteed duration
for which the projected image will maintain at least 50 percent
brightness compared with initial brightness. |
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3:2 Pulldown support |
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The capability to receive and recover an NTSC 3:2 pulldown
video signal to display the original 24 fps format of a standard
film video. This procedure enables the projector to display
film-like image quality while receiving a 3:2 pulldown signal.
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Colour temperature |
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At higher temperature, the screen looks colder; at lower
temperature, the screen looks warmer.
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Saturation |
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Adjusts a video image from black and white to fully saturated
colour.
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Video compatibility
(analogue) |
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| Video compatibility determines what kind
of AV signal can be accepted and work well on a projector. Typically
we say NTSC (3.58/4.43), PAL (B/D/G/H/I/M/N) or SECAM (B/D/G/K/K1/L)
analogue signal compatible. |
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Video compatibility
(digital) |
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| Defines the compatibility with various digital
TV signal formats, like HDTV - High Definition TV (720p, 1080i),
EDTV - Enhanced Digital TV (480p, 576p) and SDTV - Standard
Definition TV (480i, 576i) where the character "p"
means "progressive" or "non-interlaced"
and "i" means "interlaced": 480 stands for
NTSC format and 576 for PAL/SECAM format. |
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De-gamma |
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| Affects the representation of dark scenery.
With a greater gamma value, dark scenery will look brighter. |
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White segment adjustment |
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| For a data projector with a typical four-segment
(white, red, green and blue) colour wheel, the feature of white
segment adjustment provides an option to improve the saturation
and correctness of displayed colour. Larger white segments provide
higher brightness but sacrifice colour performance. |
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Movie mode (projection
scenario) |
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| The image mode option provides a few sets
of preset configurations to fit various projection scenarios;
such as "Movie", "Video", "Image",
and "PC". |
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