Method for correcting measurement values during measurements of a particle volume flow by means of shadowgraphy, the methods comprising the steps of: - calibrating a shadowgraphy imaging device; - generating high-resolution shadowgraphy images of a particle volume flow using the calibrated shadowgraphy imaging device; - evaluating of the high-resolution shadowgraphy images; - calculating measurement values of the particle volume flow; and - correcting calculated measurement values of the particle volume flow taking into account the value of the gradient slope GS, wherein the value of the gradient slope GS corresponds to the value of a normalized intensity decrease per pixel at a detected particle edge or point edge, characterized in that the step of calibrating further comprises: - for each of the plurality of predefined calibration point diameters d p real : determining a corresponding parameter range on the basis determined ratio between the predefined calibration point diameter d p real and the corresponding measured calibration point diameter d p raw and the corresponding gradient slope GS , wherein each measured calibration point diameter d p raw with corresponding gradient slope GS, which is located within this corresponding parameter range, is assigned a corrected calibration point diameter d p corrected , the value of the corrected Calibration point diameter d p corrected corresponding to the value of the respective predefined calibration point diameter d p real of this corresponding parameter range; - limiting the determined corresponding parameter ranges by a minimum gradient slope GS min - calibrating a shadowgraphy imaging device; - generating high-resolution shadowgraphy images of a particle volume flow using the calibrated shadowgraphy imaging device; - evaluating of the high-resolution shadowgraphy images; - calculating measurement values of the particle volume flow; and - correcting calculated measurement values of the particle volume flow taking into account the value of the gradient slope GS, wherein the value of the gradient slope GS corresponds to the value of a normalized intensity decrease per pixel at a detected particle edge or point edge, characterized in that the step of calibrating further comprises: - for each of the plurality of predefined calibration point diameters d p real : determining a corresponding parameter range on the basis determined ratio between the predefined calibration point diameter d p real and the corresponding measured calibration point diameter d p raw and the corresponding gradient slope GS , wherein each measured calibration point diameter d p raw with corresponding gradient slope GS, which is located within this corresponding parameter range, is assigned a corrected calibration point diameter d p corrected , the value of the corrected Calibration point diameter d p corrected corresponding to the value of the respective predefined calibration point diameter d p real of this corresponding parameter range; - limiting the determined corresponding parameter ranges by a minimum gradient slope GS min - for each of the plurality of predefined calibration point diameters d p real : determining a corresponding parameter range on the basis determined ratio between the predefined calibration point diameter d p real and the corresponding measured calibration point diameter d p raw and the corresponding gradient slope GS , wherein each measured calibration point diameter d p raw with corresponding gradient slope GS, which is located within this corresponding parameter range, is assigned a corrected calibration point diameter d p corrected , the value of the corrected Calibration point diameter d p corrected corresponding to the value of the respective predefined calibration point diameter d p real of this corresponding parameter range; - limiting the determined corresponding parameter ranges by a minimum gradient slope GS min <EOS>