Some molecules and minerals—including a number of mineral pigments—exhibit infrared fluorescence (IRF). This phenomenon is analogous to ultraviolet fluorescence, in which excitation by ultraviolet radiation produces an emission in the visible range. In infrared fluorescence, by contrast, excitation occurs within the ultraviolet or visible region of the spectrum, and the material re-emits radiation at longer wavelengths, in the near-infrared.

This behavior arises from the interaction of light with the electronic and vibrational energy states of the material, leading to a characteristic luminescent response. Because the emitted radiation lies beyond the visible range, infrared fluorescence is not perceptible to the human eye and must be recorded using cameras sensitive to near-infrared wavelengths.

In the context of art examination, IRF can provide valuable information for the identification of specific pigments and materials, as different substances exhibit distinct fluorescence responses. It is therefore a useful complementary technique within technical photography, alongside methods such as ultraviolet fluorescence and infrared reflectography.