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By comparison, a 60-watt household incandescent lamp will produce about 900 lumens. The luminous efficacy or lumens produced per watt of input of flashlight bulbs varies over the approximate range of 8 to 22 lumens/watt, depending on the size of the bulb and the fill gas, with halogen-filled 12-volt lamps having the highest efficiency.
2012: Mini Maglite AA Pro 215 Lumens and Mini Maglite AA Pro+ 245 Lumens. 2012: Maglite 2D pro 274 Lumens with a Cree XP-G rather than a Cree XP-E, increasing brightness while decreasing beam distance efficiency. 2012: Maglite Mag-Tac flashlight plain bezel, 310 Lumens, low mode at around 100 Lumens. First Maglite flashlight to use CR123A ...
For example, if the guide number is 100, and the shutter traverse time is 5 ms (a shutter speed of 1/200s), and the shutter speed is set to 1 ⁄ 2000 s (0.5 ms), the guide number reduces by a factor of √ 0.5 / 5, or about 3.16, so the resultant guide number at this speed would be about 32.
The term candlepower was originally defined in the United Kingdom, by the Metropolitan Gas Act 1860, as the light produced by a pure spermaceti candle that weighs 1 ⁄ 6 pound (76 grams) and burns at a rate of 120 grains per hour (7.8 grams per hour).
A photograph showing two Fulton MX-991/U Flashlights, next to an unofficial reproduction and a standard angle-head flashlight. The MX-991/U Flashlight (aka GI Flashlight, Army flashlight, or Moonbeam [1]) from the TL-122 military flashlight series of 1937-1944 and is a development of the MX-99/U flashlight issued in 1963 [clarification needed].
An extremely high voltage pulse, (usually between 2000 and 150,000 volts), the "trigger pulse", is applied either directly to or very near the glass envelope. (Water-cooled flashtubes sometimes apply this pulse directly to the cooling water, and often to the housing of the unit as well, so care must be taken with this type of system.)
Modern emergency floodlights provide a high-lumen, wide-coverage light that can illuminate an area quite well. Some lights are halogen, and provide a light source and intensity similar to that of an automobile headlight. Early battery backup systems were huge, dwarfing the size of the lights for which they provided power.
In the US lighting industry, foot-candles are a common unit of measurement used by architects to calculate adequate lighting levels. Foot-candles are also commonly used in the museum and gallery fields in the US, where lighting levels must be carefully controlled to conserve light-sensitive objects such as prints, photographs, and paintings, the colors of which fade when exposed to bright ...