Radiometry provides methods and quantities for the characterization of the intensity of radiation with emphasis on applications in optical metrology. Whenever the signal in an optical sensor in combination with the associated lighting system must be estimated, the quantities and concepts of radiometry come into play. Should you like to know whether 10 LEDs will produce a sufficiently high lighting level in the field of view to saturate your camera signal, it my be a good idea to brush-up your knowledge about radiometry. The same holds true when you look at the data sheets of light sources or lighting systems from different manufacturers.