Lustre

Lustre, the characteristic appearance of a bright metallic surface, or of air within glass under water as seen under certain angles of total reflection (see REFLECTION). It is supposed to be due to the conflict between the images in the two eyes, which do not coincide in respect of brightness all over the field. A similar result may be obtained by looking with one eye at a white-and-black and with the other at a black-and-white object, the form, sizes, and positions of the objects being such as would otherwise have enabled the observer to blend them into a single stereoscopic image (see STEREOSCOPE); the opposition of brightness makes the stereoscopic binocular image assume a lustrous appearance.