The methods and technical means of mineral exploration are very diverse. One of them is the method of recording radiance (brightness) contrasts of the Earth's surface in the infrared region of the spectrum, which, in combination with others (photographic, magnetometric, etc.), can provide useful information. The article discusses the physical conditions for the existence of radiance contrasts caused by inhomogeneities in the structure of the Earth's layers, as well as some issues concerning the possibility of recording and calculating them. ...