Most camera sensors use a single layer of photosites (pixels). These are only sensitive to light, not colour, so a mosaic of red, green and blue filters (the ‘bayer pattern’) is placed on top of the sensor’s photosites so that individually they capture red, green or blue light. When the camera processes the sensor data to produce an image, it ‘demosaics’ the red, green and blue data, using colour information from surrounding photosites to ‘interpolate’ full colour data for each pixel.