A spectrometer enables the spectral decomposition of optical radiation. The term spectral radiometry is used if an absolute calibration is used for the spectrometer.
In general, a spectroradiometer decomposes the impinging light into its spectral components and detects them independently e. g. with the help of a CCD array or a scanning monochromator. In comparison, an integral detector only interprets a signal in terms of its intensity according to its own spectral sensitivity while the spectral information is lost.
Most applications particularly require highly precise spectral information.