The halide used widely in photography is

Silver halide or silver salt is mostly used in photographic films

Explanation:

Silver halide crystals in gelatin are coated onto a film base, glass or paper substrate. And when a sliver halide crystal is exposed to light (photons strike) it turned into a small speck of metallic crystal and these comprise the invisible or latent image which is developed afterwards.

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.