1. A display device for displaying a visual image, said device comprising: means for filtering an input electrical video signal to produce a filtered electrical video signal, said input electrical video signal including signal components each having a component frequency, and means for producing a visual optical image from the filtered electrical video signal, said means for producing the visual optical image being such that the visual optical image is formed as an array of individual picture elements, said picture elements being arrayed so as to have a characteristic spatial frequency, wherein said means for filtering the electrical video signal operates in dependence upon the characteristic spatial frequency of the array of picture elements, and substantially attenuates components having component frequencies above a pre-filter cutoff frequency.