Here is the second part of our glossary series on LED terminology, from M to Z.
Matrix: 1. a two-dimensional array, that is, an array of rows and columns. 2. the height and width of a display, measured in rows and columns of pixels (for example, 8x48 = eight rows high by 48 columns wide).
Milli-candela (mcd): One thousandth of a candela
Nit, nits: Nit is defined as a luminance unit equal to one candela (one candle) per square meter measured perpendicular to the rays from the source. From the Latin word nitere, meaning "to shine"; nits are used to measure display intensity, or brightness. Nits, when used in conjunction with contrast ratio and viewing angle, determine the quality of the image in the desired application.
Out of Home: All advertising that is specifically intended to reach consumers outside the home. Out of home includes, but is not limited to, outdoor media and radio.
Outdoor Advertising: The term refers to many forms of media that carry advertising messages to consumer audiences outside the home. Outdoor products are divided among three primary categories, billboards, street furniture and transit.
Panels: A cluster of modules built into a housing.
Physical Pitch Resolution: The measured distance between the same diode within adjacent pixels. Pixel The smallest single point of light on a display that can be turned on and off. For LED displays, a pixel is the smallest block of light emitting devices that can generate all available colors. For incandescent displays, a pixel is an individual lamp on the matrix.
Pitch: The distance from the center of a pixel to the center of the next pixel. Pitch influences the resolution of a LED display that shows images. A small pitch translate to higher resolution. A large pitch translates to larger text/character sizes. The picture to the right indicates how pitch is measured.
Proof-of-Performance: Certification by an outdoor company that contracted advertising services have been rendered.
Reach: The approximate percentage of a target audience's population which will be potentially exposed to an advertising message at least once during a specified period of time. Reach is normally measured over four week periods. Common to all media.
Readability Angle: The angle at which the LEDs on a sign can still be seen and/or read. The readability angle, which is dependent on ambient light and site conditions, is much larger than the viewing angle. For instance, a 30° readability angle LED sign can easily be read at angles greater than 90° at night. In an instance where the LEDs have been dimmed to less than 50 percent, for example, a viewer would still be able to see or read the LEDs, hence the greater angle than in viewing angle. Readability angle is largely subjective and difficult to measure. (see viewing angle)
Refresh rate: The number of times per second the screen is updated or "repainted." Depending on the video standard, the actual image is changed only 30 times per second for NTSC signal or 25 times per second for PAL. However, most LED systems use pulse-width modulation to generate the color levels, and if the image were only "painted" once for every change, there would be a noticeable flicker on the display. A refresh rate of greater than 60 times per second will minimize the flicker. In general, LED displays should be refreshed at 120 times per second (120 Hz) or greater.
Remote control: Control of a display from a remote and/or central location via a communications network.
Resolution: The basic measurement of how much information is displayed on a screen, expressed in units of pixels. Resolution is determined by the pixel pitch and the physical dimensions of the display. To calculate resolution, divide the area of the display by the area of an individual pixel. Most displays of video quality have a resolution greater than 10,000 pixels. Generally, the greater the resolution, the better the image will appear. Commonly listed as number of pixels per square meter.
RGB: Red-green-blue. In video displays, web design, and design for computer monitors, colors are defined in terms of a combination of these three colors. For example, the RGB abbreviation for the color blue is 0-0-255. In contrast, print designers typically define colors using cyan-magenta-yellow-black, or CMYK.
Sign: Any structure used to display information regarding a product or service. An outdoor unit is a sign.
Spectacular: A bulletin that is usually larger than 14' x 48' and is positioned at prime locations in a market. A spectacular often utilizes special embellishments.
Traffic Count: The recording of the vehicles and pedestrians passing a given point; used by TAB to authenticate the potential exposure of outdoor advertising structures.
Viewing Angle: The area that will provide optimum viewing of a display. The angle is determined by the horizontal and vertical points at which the measured light intensity is 50 percent of that measured directly in front of the display.
Viewing Distance: In general, the distance from a sign that text can be read. For digital displays, the maximum viewing distance is gauged by the readability of the entire display. It is generally accepted that for every 1' of display height, there is a viewing distance of 40' (40:1 ratio). For example, an 8' display could reasonably be viewed at a distance of 320'. For traditional matrix displays, the maximum viewing distance is gauged by using the smallest text character (using a 7-pixel-high font). The accepted standard is that displays gain 50' of viewing per inch of character height. For example, using a 7-high font for a 1.5" pixel (character height = 7 pixels x 1.5" = 10.5"), the viewing distance would be 525'. (10.5 x 50' = 525). The minimum viewing distance is defined as the closest distance at which the colors from an individual pixel begin to blend with the surrounding pixels.
Visual Resolution: The effective resolution on the display as perceived by the human eye.
