In his General Theory of Relativity, announced in 1916, Albert Einstein postulated that light is bent by gravity. Three years later, on the occasion of a total eclipse of the sun in 1919, a group of British astronomers in Africa proved this hypothesis to be true by measuring the effects on light from stars shining on earth from close to the sun's disc. The discovery, however, led to the anticipation that light from faraway astronomical objects is bent by the gravity of closer, highly dense objects, and is perceived on earth as if through a magnifying camera lens. This phenomenon became known as the Gravitational Lens Effect. Advancements in telescopes and observation instruments, as well as the tirelsefforts of astronomers, led to the discovery in 1979 of an object acting as a gravitational lens. The discovery came 100 years after the birth of Einstein.

There exist other phenomena of bending light in addition to gravity, such as reflection, refraction and diffraction. Reflection has been the most widely known light bending method, used in a variety of fields, and refraction also came into wide application in lenses and prisms. On the other hand, the diffractive phenomenon, while vital as a method to determine the crystal structure of substances in scientific fields, has very limited commercial applications, mostly because of the extremely high-level manufacturing technologies required to create diffractive optical elements.

Canon's Multi-Layer Diffractive Optical Element represents a revolutionary "discovery," in that it makes possible the use of the element in camera lenses. This is a story of how gravitic efforts led to the brilliant bending of light, as we meet the engineers involved in this world's first project: the design of the element, development of production techniques, and design of the EF400mm f/4 DO IS USM super-telephoto lens, which maximizes the properties of the diffraction phenomenon.