A method of and an apparatus for obtaining spectral data and calculating corrected spectral data. The method includes the steps of: obtaining spectral data S'(.lambda.) which is representative of the spectral characteristics of light which is generated by a light source and reflected by an object; substantially concurrently with the step of obtaining the spectral data S'(.lambda.), obtaining spectral data R(.lambda.) which is representative of the spectral characteristics of light which is generated by the light source; and calculating corrected spectral data S(.lambda.) as a function of the spectral data S'(.lambda.) and the spectral data R(.lambda.).