This invention relates to holographic image display systems (200), and to related methods and processor control code. We describe a method of displaying an image holographically, the method comprising: inputting display image data defining said image for display; processing said image data to determine first image data representing a first spatial frequency portion of said image data and second image data (206) representing a second spatial frequency portion of said image data, wherein said second spatial frequency is higher than said first spatial frequency; displaying a hologram (204) of said first image data on a spatial light modulator (SLM1) to form a holographically-generated intermediate real image; onto a second spatial light modulator (SLM2) which modulates the intensity of said intermediate real image using said second image data (206) to display said image.