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Guide numbers are not affected by scene reflectance. Guide numbers are a function of the illuminance and duration of a flash (a property called luminous exposure that have lux⋅seconds as their units of measure) arriving at a scene as measured by an incident-light meter (pictured at right), not the amount leaving the scene.
Infrared LEDs are used in remote-control circuits, such as those used with a wide variety of consumer electronics. The first visible-light LEDs were of low intensity and limited to red. Early LEDs were often used as indicator lamps, replacing small incandescent bulbs, and in seven-segment displays.
Most of these were connected to the set being controlled by wires, but the Philco Mystery Control (1939) was a battery-operated low-frequency radio transmitter, [14] thus making it the first wireless remote control for a consumer electronics device. Using pulse-count modulation, this also was the first digital wireless remote control.
These lenses come in a variant of colors, mainly clear, yellow, amber, red, blue, and green. The lens color can affect the intensity of light. [5] LED strobe beacons consist of a base, a LED or group of LEDs, and a cover. A solid state flash controller is located within the base, which allows the LED beacon to operate in a variety of flash ...