Visible, or patent, fingerprints are clear to the naked eye, and left on a surface with blood, ink or other liquid substance. Latent fingerprints are not visible to the naked eye because it is just oil residue left behind from a person's fingertips. These prints are only visible through further processing, such as dusting with powder. Plastic fingerprints are a third type that is left behind in putty, mud or a similar substance.
A good example of a visible, or patent, fingerprint are the prints collected by police when a person is arrested and booked. The police press a person's finger in ink, then apply it to paper to collect a patent fingerprint. Both patent and plastic fingerprints are collected at crime scenes by law enforcement and detectives by taking a picture because these prints are easily visible to the naked eye. Latent fingerprints need more processing in order to collect them. The process used depends on the surface on which the fingerprints are left. If the print is left on a non-porous smooth surface, aluminum powder is dusted over the print. The powder sticks to residue and a picture can then be taken of the print. When the print is left behind on a porous or rough surface, chemical treatments are used to make the print visible.