In practice, glare is almost always a situation where a source of unshielded light is at least 1,000 times brighter than the average visual field. For instance, since the night sky is dark, almost all outdoor light sources, such as a street luminaire or automobile headlight, cause glare. To evaluate glare, however, light can't be measured in lux or footcandles—one must use luminance, which typically is measured in candelas per square meter (cd/m2) or nits. It also is common, although not technically correct, to use the term brightness rather than luminance.

The "invention" of chiaroscuro is often attributed to the Italian renaissance painter Caravaggio. Caravaggio was seen as a rebellious painter who often defied traditional rules. Whereas some painters would place their art in areas with specific lighting to accentuate certain features, Caravaggio set out to reproduce this effect in the paintings themselves.