Appendix: Glossary - Dell M900HD User Manual

Web Management
7
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).
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.
dB — decibel — A unit used to express relative difference in power or
intensity, usually between two acoustic or electric signals, equal to ten
times the common logarithm of the ratio of the two levels.
Diagonal Screen — A method of measuring the size of a screen or a
projected image. It measures from one corner to the opposite corner. A 9
80 Glossary
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Appendix: Glossary