A semiconductor color image sensor comprises: an array of semiconductor photo-sensors (CMOS or CCD) and a color filter array comprising an array of red, green and blue filter elements in which each filter element is associated with a respective one of the photo-sensors. The sensor further comprises a phosphor (photo-luminescent) material associated with each of the blue filter elements and configured to absorb blue light and re-emit light of a longer wavelength range which is then incident on the photo-sensor associated with the blue filter element. Preferably the phosphor material is selected such that light of the longer wavelength range substantially matches the spectral response of the photo-sensor. The image sensor can further comprise an array of micro-lenses for focusing light onto the photo-sensors of the image sensor, wherein each micro-lens is associated with a respective one of the photo-sensors.