A method for processing data for display on a screen, the method comprising the steps of: encoding, using a first colour space, a first portion of image data intended to be displayed on a first area of the screen; encoding, using a second colour space, a second portion of image data intended to be displayed on a second area of the screen; compressing the encoded first and second portions of the image data for transmission; and transmitting the compressed image data over a link for display on the screen; further comprising: providing a model of the sensitivity of a viewer to light displayed at different locations on the screen; and selecting the first and second colour spaces and defining the first and second areas of the screen based on the model of the sensitivity of the viewer, wherein the model of the sensitivity of a viewer to light comprises a measure of the sensitivity of the viewer to at least one of: chrominance, luminance, and light of different wavelengths; further comprising defining the first and second areas of the screen by: comparing the modelled sensitivity of the viewer across the screen to a threshold sensitivity; defining an area of the screen for which the modelled sensitivity is above the threshold sensitivity as the first area of the screen; and defining an area of the screen for which the user sensitivity is below the threshold sensitivity as the second area of the screen; wherein: the first colour space is based on a colour model having at least a luminance component and a chrominance component, preferably two chrominance components; and the second colour space is based on a colour model having three colour components, preferably wherein: the colour model having three colour components is based on RGB, and the colour model having a luminance and two chrominance components is based on YUV. encoding, using a first colour space, a first portion of image data intended to be displayed on a first area of the screen; encoding, using a second colour space, a second portion of image data intended to be displayed on a second area of the screen; compressing the encoded first and second portions of the image data for transmission; and transmitting the compressed image data over a link for display on the screen; further comprising: providing a model of the sensitivity of a viewer to light displayed at different locations on the screen; and selecting the first and second colour spaces and defining the first and second areas of the screen based on the model of the sensitivity of the viewer, wherein the model of the sensitivity of a viewer to light comprises a measure of the sensitivity of the viewer to at least one of: chrominance, luminance, and light of different wavelengths; further comprising defining the first and second areas of the screen by: comparing the modelled sensitivity of the viewer across the screen to a threshold sensitivity; defining an area of the screen for which the modelled sensitivity is above the threshold sensitivity as the first area of the screen; and defining an area of the screen for which the user sensitivity is below the threshold sensitivity as the second area of the screen; wherein: the first colour space is based on a colour model having at least a luminance component and a chrominance component, preferably two chrominance components; and the second colour space is based on a colour model having three colour components, preferably wherein: the colour model having three colour components is based on RGB, and the colour model having a luminance and two chrominance components is based on YUV. providing a model of the sensitivity of a viewer to light displayed at different locations on the screen; and selecting the first and second colour spaces and defining the first and second areas of the screen based on the model of the sensitivity of the viewer, wherein the model of the sensitivity of a viewer to light comprises a measure of the sensitivity of the viewer to at least one of: chrominance, luminance, and light of different wavelengths; further comprising defining the first and second areas of the screen by: comparing the modelled sensitivity of the viewer across the screen to a threshold sensitivity; defining an area of the screen for which the modelled sensitivity is above the threshold sensitivity as the first area of the screen; and defining an area of the screen for which the user sensitivity is below the threshold sensitivity as the second area of the screen; wherein: the first colour space is based on a colour model having at least a luminance component and a chrominance component, preferably two chrominance components; and the second colour space is based on a colour model having three colour components, preferably wherein: the colour model having three colour components is based on RGB, and the colour model having a luminance and two chrominance components is based on YUV.