One of the fascinations of photography as an art or a science is that it enables us to see more than the eye can see.

"The sensitive photographic film is the true retina of the scientist . . . for it possesses all the properties which science could want: it faithfully preserves the images which deposit themselves upon it, and reproduces and multiplies them indefinitely on request; in the radiative spectrum (electromagnetic spectrum) it covers a range more than double that which the eye can perceive and soon perhaps will cover it all: finally it takes advantage of that admirable property which allows the accumulation of events, and whereas our retina erases all impressions more than a tenth of a second old, the photographic retina preserves them and accumulates them over a practically limitless time" PJC Janssen 1888

Ultraviolet fluorescence of tonic water, due to quinine, seen with a long exposure as it is poured into a wine glass.