V4, where the light reflected from a surface is compared with that reflected from surrounding surfaces, in order to control for relative rather than absolute brightness.

ECONOMIST: The biology of art | The

This handheld device measures the different wavelengths or types of light reflected from a surface.

NPR: Using Science to Rescue Art

But with future telescopes, scientists say it may be possible to see past the blinding glare of the parent star to pick out just the faint light passing through a small world's atmosphere or even reflected off its surface.

BBC: Kepler telescope spies 'most Earth-like' worlds to date