NIST to launch a dramatically improved system for measuring the intensity and spectrum of light
(PHYSorg.com Physics)

We see the world in reflection: Nearly all the light that enters our eyes has bounced off something first, bringing with it information about the nature of the objects it encountered on the way. But that information is strongly affected by the angle at which the light strikes the object, and also the angle at which the reflected light reaches the eye of the beholder.