An image synthesizing method and apparatus for forming a composite image from basic images with complex image values acquired by sensors having sensitivities which vary differently across the area to be imaged, includes the deviation of complex image values of the composite image from the image values of the basic images which have been weighted in dependence on the complex values of the sensitivity of the sensors. The complex sensitivity values are determined according to the invention in that the sensitivities of the sensors are estimated on the basis of the basic images themselves by determining the sensitivity of each sensor from the basic image acquired thereby.