The invention relates to a method for determining characteristic-curve correction factors a matrix detector that images in the infrared spectral range. A good image correction can be obtained by virtue of an area of homogeneous temperature being recorded at two different temperatures by the matrix detector, there being two images with different integration times for each temperature. A signal gradient over the integration time is established for each of the pixels from the four pixel values at the two temperatures in each case and the gain being established from the difference of the signal gradients and characteristic-curve correction factors for the gain being stored.