A method of analyzing a specimen using X-rays, comprising the steps of: Irradiating the specimen with input X-rays; Using a detector to detect a flux of output X-rays emanating from the specimen in response to said irradiation, which method further comprises the following steps: Using the detector to intercept at least a portion of said flux so as to produce a set {Ij} of pixeled images Ij of at least part of the specimen, whereby the cardinality of the set {Ij} is M>1. For each pixel pi in each image Ij, determining the accumulated signal strength Sij, thus producing an associated set of signal strengths {Sij}. Using the set {Sij} to calculate the following values: A mean signal strength S per pixel position i; A variance σ2S in S per pixel position i. Using these values S and σ2S to produce a map of mean X-ray photon energy E per pixel.