An instrument for measuring a property of light, especially luminous intensity or flux. A photometer uses special colored filters to replicate the response of the human eye. Light intensity is measured in candle power, usually by comparison with a standard source.
An instrument for measuring the intensity of light or the relative intensity of a pair of lights. Also called an illuminometer. If the instrument is designed to measure the intensity of light as a function of wavelength, it is called a spectrophotometer. Photometers may be divided into two classes: photoelectric photometers in which a photoelectric cell is used to compare electrically the intensity of an unknown light with that of a standard light; and visual photometers in which the human eye performs the function of a photo cell. A photometer used to measure the intensity of a distant light is referred to as a telephotometer or transmissometer.
A photometer is a meter that measures visible Illuminance light levels. The basic unit of luminance measurement is Candela per square meter (cd/m2). Both Lux and Candelas measure luminous intensity from a specific direction.
A light meter which when attached to the eyepiece of a telescope can measure the brightness of stars. The photometer will read out a number proportional to brightness. If we first look at stars whose brightness we know, we can use our photometer to measure the brightness of a unknown star. We use the SSP-3 photometers made by OPTEC Inc.
An instrument for measuring the luminance, luminous intensity, or illuminance of a light source. Analogous to radiometer, but with an output weighted by the wavelength response of the human eye (i.e., scaled by luminous efficiency). It is common in historical literature to see this term used for any radiometer that responds primarily to wavelengths that are visible to the human eye, with or without scaling for luminous efficiency. A photometer used to measure the intensity of a distant light is sometimes referred to as a telephotometer or transmissometer. See hydrophotometer, radiometer.