A method for analyzing a digital image channel comprising the steps of providing a digital image channel, extracting a signal from the digital image channel, and using the extracted signal to determine whether the digital image channel is an interpolated digital image channel or a non-interpolated digital image channel. More specifically, the extracted signal comprises a signal related to differences between the values of neighboring pixels of the digital image channel, and the periodicity of the extracted signal is analyzed by computing a Fourier Transform signal of the extracted signal and looking for peaks in the Fourier Transform signal.