Irradiating bathers

Seurat's rightly-famous painting "The Bathers" has many interesting features, including the use of irradiation. That is to say that if a light object is placed on a darker background, then it appears even lighter. So certain light objects (e.g. the bathers' skin) are enhanced by darkening their backgrounds (e.g. the water) in a way that is a) totally artificial and b) very pleasing. This has been known for centuries, and is an example of simultaneous brightness contrast. The eye is not trying to tell us exactly how the world is, but only allowing us to behave usefully in the world.

Irradiation also refers to bombarding objects with radio waves (such as gamma or x-rays), typically in order to sterilise food. When anthrax was sent through the US mail repeatedly a few years back, the postal service started routinely irradiating parcels and letters. This led indirectly to the bankruptcy of at least three mail-order cheese companies, whose products were irradiated to the extent that the mould in the blue-cheeses was killed, along with widespread problems regarding magenetic tapes, photographic films and slides becoming corrupted.