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Use in Photography Several systems of light meter have been used the three most common being Selenium , CdS , and Silicon light meters. , USSR )]] Movie Camera , based on a galvanometer mechanism (center) and a CdS Photoresistor , in opening at left.]] Selenium and silicon light meters use sensors that are Photovoltaic . These sensors generate a voltage proportional to light exposure. Selenium sensors generate enough voltage for direct connection to a meter. Silicon sensors need an amplification circuit and require a power source like a Batteries to operate. CdS light meters use a sensor based on Photoresistance . These also require a battery to operate. Most modern light meters use silicon or CdS sensors. They indicate the exposure either with a needle Galvanometer , or on a LCD screen. Many modern consumer still and video Camera s include a built-in meter that measures a scene-wide light level and are able to make an approximate measure of appropriate exposure based on that. Professional photographers and motion picture Cinematographer s generally use handheld ambient light meters to precisely measure the light falling on various parts of their subjects, and use suitable lighting to produce the desired exposure levels. Use in illumination Light meters or light detectors are also used in illumination. Their purpose is to measure the illumination level in the interior and to switch off or reduce the output level of luminaires. They can greatly reduce the energy burden of the building by significantly increasing the efficiency of lighting system. It is known, that 20 to 60 percent of all electrical power in a building is consumed by illumination. It is therefore recommended to use light meters in lighting systems especially in rooms, where one cannot expect users to pay attention to manual switching off the lights. These are: hallways, stairs, big halls etc. There are, however, significant obstacles to overcome in order to achieve a succesful implementation of light meters in lighting systems, of which user-acceptance is by far the most formidable. Unexpected or too frequent switching and too bright or too dark rooms are very annoying and disturbing for users of the rooms. Therefore, different switching algorithms have been developed:
See also Illumination: PIN Diode , Lighting Design , Photomultiplier Tube External links |
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