A device, comprising: - a light source; - a first means (12, 16, 37) comprising first controllable elements and being configured to spatially modulate the light of the light source at a first spatial resolution; - a spatial light modulator comprising second controllable elements having a higher resolution than the first spatial resolution; - an optical arrangement (17, 27) that causes light from the first controllable elements of the first means to be imaged onto the spatial light modulator; and - a controller; wherein: - the controller is configured to cause light from the first controllable elements of the first means to form a low resolution version of an image; - light from each first controllable element of the first means imaged onto the spatial light modulator corresponds to a plurality of controllable elements of the spatial light modulator; - the variation in intensity with position of light from each of the first controllable elements of the first means is represented by the convolution of a square profile and a spread function that causes the light to spread into areas corresponding to adjacent first controllable elements so as to cause a smoothly varying light intensity from one first controllable element of the first means to other first controllable elements of the first means and - the controller is configured to operate the spatial light modulator in response to differences between the low resolution version of the image and the image determined by dividing desired luminance values by a known intensity of light incident from the first means on the corresponding controllable elements of the spatial light modulator. - a light source; - a first means (12, 16, 37) comprising first controllable elements and being configured to spatially modulate the light of the light source at a first spatial resolution; - a spatial light modulator comprising second controllable elements having a higher resolution than the first spatial resolution; - an optical arrangement (17, 27) that causes light from the first controllable elements of the first means to be imaged onto the spatial light modulator; and - a controller; - the controller is configured to cause light from the first controllable elements of the first means to form a low resolution version of an image; - light from each first controllable element of the first means imaged onto the spatial light modulator corresponds to a plurality of controllable elements of the spatial light modulator; - the variation in intensity with position of light from each of the first controllable elements of the first means is represented by the convolution of a square profile and a spread function that causes the light to spread into areas corresponding to adjacent first controllable elements so as to cause a smoothly varying light intensity from one first controllable element of the first means to other first controllable elements of the first means and - the controller is configured to operate the spatial light modulator in response to differences between the low resolution version of the image and the image determined by dividing desired luminance values by a known intensity of light incident from the first means on the corresponding controllable elements of the spatial light modulator.