One of the uses of TIFF/EP is as a raw image format. A characteristic of most digital cameras (but excluding those using the Foveon X3 sensor or similar, hence especially Sigma cameras) is that they use a color filter array (CFA). Software processing a raw image format for such a camera needs information about the configuration of the color filter array, so that the raw image can identify separate data from the individual sites of the sensor. Ideally this information is held within the raw image file itself, and TIFF/EP uses the tags that begin "CFA", CFARepeatPatternDim and CFAPattern, which are only relevant for raw images.