A method of holographic projection includes projecting at least one calibration image. The method includes performing the following steps for each calibration image in order to determine a plurality of displacements vectors at a respective plurality of different locations on the replay plane: projecting the calibration image onto the replay plane using a first colour holographic channel by displaying a first hologram on a first spatial light modulator and illuminating the first spatial light modulator with light of the first colour; projecting the calibration image onto the replay using a second colour holographic channel by displaying a second hologram on a second spatial light modulator and illuminating the second spatial light modulator with light of the second colour, the first and second hologram corresponding to the calibration image; determining the displacement vector between the light spot formed by the first colour holographic channel and the light spot formed by the second colour holographic channel; and pre-processing an image for projection using the second colour holographic channel in accordance with the plurality of determined displacement vectors.