- photometer - measuring instrument for measuring the luminous intensity of a source by comparing it (visually or photoelectrically) with a standard source
--1 is a kind of measuring instrument, measuring system, measuring device
--1 has particulars: spectrophotometer- light meter, exposure meter, photometer - photographic equipment that measures the intensity of light
--2 is a kind of photographic equipment
--2 has particulars: cytophotometer - light meter, exposure meter, photometer - photographic equipment that measures the intensity of light