From Light Houses to Black Boxes: The Fresnel Lens

In theatre, we generally use a fresnel (fer-nel) to throw a wash onto the stage.  Without the lighthouse, this theatrical workhorse would not exist. The fresnel actually gets its name from its lens, which was invented by Augustin-Jean Fresnel.  Fresnel was designing a larger plano-convex glass lens.  To make a plano-convex lens in large sizes required large amounts of glass, making the lenses too heavy and difficult to work with.  Fresnel cut away excess glass into concentric rings and focused all the rings in the same area.  This made the lens just as effective, but lighter and thinner than the plano-convex lens.  The new lens also collected more light and threw the light further than previous designs. How did a fresnel lens get from the lighthouse into the theatre? fresnel-and-fresnel A fresnel lens offered a lot of unique characteristics that were helpful in theatre.  The lens was light weight and thinner than other glass lenses.  The glass heated evenly, reducing cracking. The soft edge allowed it to blend with other fresnels to give an even wash of light and color.  Fresnels also featured an adjustable beam size, by moving the lens within the fixture. In their 1969 catalog, the Kliegl Brothers claimed the first use of the fresnel lens in a theatrical fixture.  And the rest, is history.





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