2 Fingerprints in identification

The matching of fingerprint details has actually changed rather little since Galton's day. In images of fingerprints, it is important to remember that the ridges are normally shown in black (or sometimes another colour) on a white or light background. This is the way that dirty fingers leave prints on light coloured surfaces and how inked fingers transfer prints to paper for the storage of fingerprint data, as it is the ridges that touch the surface.