Instrument Systems GmbH Munich is a leader indeveloping and manufacturing high-precision light measurement systems. With the new offer of stray light correction during the calibration of array spectrometers, Instrument Systems now is the first company to serve the broad market. By including a stray light correction matrix in the calibration process, it is possible to suppress the stray light during the measurement by an order of magnitude down to 10-5. A 10% higher sensitivity in the UV range after stray light corrected calibration leads to about 3-4% higher accuracy in the radiometric measurement. The more accurate determination of the radiometric values of UV LEDs facilitates their characterization and development, and supports the various applications of these radiation sources, for example, in the field of coating, curing, disinfection or biomedicine.