Abstract: A computer-implemented method of transmitting through a disordered medium from a transmitter to a receiver an image represented as input coherent electromagnetic radiation, the disordered medium having a transmission matrix comprising a plurality of complex-valued transmission constants that relate said input coherent electromagnetic radiation to output electromagnetic radiation at said receiver, which method comprises the steps of: performing a characterising process on said disordered medium to determine said transmission matrix; using said transmitter to transmit said image through said disordered medium; performing a reconstruction process using said transmission matrix to generate a reconstructed image from the output electromagnetic radiation at said receiver; wherein in said characterisation process the step of determining said transmission matrix comprises: determining said complex-valued transmission constants as real-valued transmission constants by using an approximately linear relationship bet