files contain 24-bit colour information, allowing up to 16.7 million colours. They use a ‘lossy’ compression method, where some image information is thrown away rather than just being stored more efficiently. A sliding scale is used to choose the level of compression; medium or high settings should avoid visible degradation. JPEG files are ideal for photographic images, but not for flat colour, as unwanted mottling can occur. Because some data is lost with each save, you should keep uncompressed copies of images that you save as JPEGs.