Method for improving the ability to detect materials in an X-ray test system, having the following method steps - at least two absorption X-ray images of an object to be investigated are recorded at different energies - the object is mathematically modelled by means of a number of layers, assuming a specific material for each layer, wherein an absorption value describes the absorptivity of a layer, the number of layers is less than or equal to the number of X-ray images and a material to be detected during the test is assumed for at least one layer - the absorption value for each layer is broken down into a travel-dependent factor and an energy-dependent factor - the travel-dependent factors for all layers are calculated from the absorption X-ray images by means of the absorption equation - at least one synthetic image is calculated from the sum of the absorption values for all layers, which absorption values have been multiplied by weighting factors - the synthetic image is evaluated.