The amount of light is measured with a light meter. In photography a light meter is often used to determine the proper exposure setting on a camera to achieve good results. Normally in this application a light meter will include a computer, either digital or analogue to allow the photographer to determine which shutter speed and f-number should be selected for optimum exposure in a certain lighting situation and film speed. They have many uses in different sectors including leisure, commercial and industrial. There are two basic designs which use this technology, being reflected light meters and incident light meters. Reflected light meters measure the light that is reflected from the scene to be photographed and are generally calibrated to show the appropriate exposure for average scenes. Incident light meters measure the amount of light falling on the subject using an integrating sphere which is placed on top of the light sensor. Applications using this technology include photography, cinematography, scenic design, light pollution control and can also be employed in a lighting environment where it can measure the amount of light and switch on and off or reduce power levels to cut down on energy costs in large buildings.
