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Glossary 127
Appendix: Glossary
ANSI Lumens — A standard for measuring the brightness. It is calculated by
dividing a square meter image into nine equal rectangles, measuring the lux (or
brightness) reading at the center of each rectangle, and averaging these nine
points.
Aspect Ratio — 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.
Brightness — The amount of light emitted from a display or projection display or
projection device. The brightness of projector is measured by ANSI lumens.
Color Temperature — The color appearance of white light. Low color
temperature implies warmer (more yellow/red) light while high color temperature
implies a colder (more blue) light. The standard unit for color temperature is
Kelvin (K).
Component Video — A method of delivering quality video in a format that
consists of the luminance signal and two separate chrominance signals and are
defined as Y'Pb'Pr' for analog component and Y'Cb'Cr' for digital component.
Component video is available on DVD players.
Composite Video — A video signal that combines the luma (brightness), chroma
(color), burst (color reference), and sync (horizontal and vertical synchronizing
signals) into a signal waveform carried on a single wire pair. There are three kinds
of formats, namely, NTSC, PAL, and SECAM.
Compressed Resolution — If the input images are of higher resolution than the
native resolution of the projector, the resulting image will be scaled to fit the
native resolution of the projector. The nature of compression in a digital device
means that some image content is lost.
Contrast Ratio — Range of light and dark values in a picture, or the ratio between
their maximum and minimum values. There are two methods used by the
projection industry to measure the ratio:
1
Full On/Off
— 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
— measures 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.
Full On/Off contrast is always a larger number than ANSI contrast for the same
projector.