52 InFocus Corporation — Introduction Guide - DLP Multimedia Projector
Glossary
Term Description
ANSI Contrast Contrast is 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. There are two methods
used by the projection industry: 1)Full On/Offcontrast 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)ANSIcontrast is measured
with 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. When comparing the contrast ratio of projectors make sure you are comparing the
same type of contrast.Full On/Offcontrast will always be a larger number thanANSIcontrast for the
same projector.
ANSI Lumens ANSI lumens is a measurement of the overall brightness of a projector. Because the center of a
projected image is brighter than the corners, ANSI lumens is the most accurate representation of
the image brightness. ANSI lumens are calculated by dividing a square meter image into 9 equal
rectangles, measuring the lux (or brightness) reading at the center of each rectangle, and averaging
these nine points.
Aperture A device that controls amount of light admitted.
Artifacts Flaws and aberrations in a video image that derive from technical limitations in the capture, encoding/
decoding, transmission, and display of a video signal.
Aspect Ratio The ratio of image width to image height. Standard television is 4:3 or 1.33:1. Panavision or
Cinemascope is 2.35:1 with 1.85:1 being quite common as well. Widescreen displays are 1.78:1 or 16:9.
times the height. For example, if you want an image 40 inches high then you need a screen that is at
least 40 * 1.78 inches wide or 71 inches. Other relatively common aspect ratios are 3:2, 4:3 and 5:4.
Bandwidth The number of cycles per second (Hertz) expressed as the difference between the lower and upper
limits of a frequency band; also, the width of a band of frequencies. Practically speaking, bandwidth
is the amount of data that can pass through a given connection per unit of time.
Barrel Distortion Distortion where screen image expands outward towards edges of the screen. Instead of being
square, edges are curved outward like the edge of a barrel. Opposite of pincushion.
Bezel The frame or face of a device, such as, a projector grill, or CRT or LCD display frame.
Black Level The darkest part of a picture. This can vary between display devices and viewing environments.
NTSC black is set at 7.5 IRE, which is very slightly gray. The white level divided by the black level gives
a contrast ratio for a particular display device.
Blackboard
Mode
Blackboard mode is a projector feature that allows the projector to detect the colour of the display
surface such as a chalkboard of painted wall and automatically adjust its output to optimize accurate
colour reproduction.
Blanking The period of time that an electron gun is turned off to reposition itself to paint the next part of the
video onto the CRT screen.
Bleeding Video distortion where colour “bleeds” from an object onto other parts of the image which are not
supposed to be that colour.
Blue Laser Colour of the laser used with Blu-ray high definition DVDs. Blue laser light has a shorter wavelength
than red, which is why blue lasers can retrieve and store more data in a given physical area.
BNC Bayonet Nut Connector or British Naval Connector. A high quality, locking cable plug which is used
extensively in professional video.
Bowing Video distortion where lines which should be straight are curved. See barrel distortion and
pincushioning.
Brightness Overall light output from an image. While a brightness control can make an image brighter, it is best
used to better define the black level of the image.
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