AV/IT Glossary—27 Days of #AVabc—K


 

 

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Keystoning/Keystone Effect—A distorted picture where one edge is not the same dimension as the opposite edge, producing a tapered or wedge shape. Typically, this results when the image is projected to the screen at an angle. It is a distortion of the image dimensions, such as making a square look like a trapezoid, the shape of an architectural keystone, hence the name of the feature. In the typical case of a projector sitting on a table, and looking upwards to the screen, the image is larger at the top than on the bottom. Some areas of the screen may not be focused correctly as the projector lens is focused at the average distance only.

 

K-kilo—An abbreviation for 1,000. A kilobyte is 1,000 bytes. Because numbers used in computer RAM sizes are in binary, the closest number is used. When talking about memory size, the numbers are rounded off (e.g. 1 kbyte is really 1,024 bytes).

KBPS (kilobits per second)—Thousands of bits per second; a measure of bit rate.

K Factor—A measure of distortion in a processed video signal, which shows on the screen or on the oscilloscope as overshoots and "ringing". Test equipment generates a special signal - a 2T-pulse - in order to measure this distortion. The distortion level is given as a percentage.

Kell Factor—The ratio between the measured number of TV lines and the pixel count of a fixed pixel video device. It equals 0.7. For example, a DVD picture with 720 pixels in the horizontal direction is equivalent to about 500 TV lines (720 x 0.7=500) of resolution.

Kelvin—An absolute scale of temperature measurement typically used to describe the color of light, expressed in “degrees Kelvin.” The lower the number, the “warmer” or redder the color of the light; a higher number indicates a “colder”, or bluer, light source. Also see "Color temperature."

Kevlar®—A brand name from DuPont for aramid yarn, used in the construction of cables to provide strength and strain relief.

Key—(1) Also called key source or key cut. A signal that can be used to electronically cut a hole in a video picture to allow for insertion of other elements such as text or another video image. The key signal is a switching or gating signal for controlling a video mixer that switches or mixes between the background video and the inserted element. (2) The composite effect created by cutting a hole in one image and inserting another image into the hole.

Key Fill—In key effects, the video signal that is said to fill the hole cut in the background video by the key source.

Keyer—An electronic circuit that creates a control signal to control a video multiplier based on selective information contained in a video signal.

Keys—See "KSV – Key Selection Vector."

kHz-Kilohertz—One thousand cycles per second (hertz).


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