Measurement of the surface temperature of continuous-cast billet is of great interest in studying ingot solidification and monitoring casting parameters [1]. However, it is difficult to measure the high surface tem perature of the continuously moving ingot among the many other moving components of the continuouscasting machine. Generally, the surface temperature of the slab at some geometric point is measured using most existing methods [2]. This is insufficient for anal ysis of the thermal state of the slab surface, since the temperature is nonuniformly distributed over the billet area. Therefore, methods of determining the thermal state of the whole slab surface have been developed recently. The new methods may be divided into two cat egories: scanning systems, in which a point-temperature sensor moves along the moving surface; and sys tems for the analysis of a mass of data obtained by means of digital cameras (thermal imaging systems) [3-5]. Thermal imaging systems are best: the tempera ture range of the cameras is from -4 0 to 2000°C, with a precision of ±2%. These systems permit the formula tion of composite video and IR images in different combinations, which facilitates analysis. However, they are very expensive. In the present work, we develop a method of assess ing the thermal state of the slab surface by the analysis of raster images obtained by means of digital photo technology that permits the use of cameras in different fields to record dynamic and static processes, with sim ple analysis of the resulting data. Digital color photos constitute a two-dimensional data set, each element of which corresponds to a point of a raster and contains three components describing the brightness of the point in three spectral regions: red R, green G, and blue B. Together, these components determine the color of the point on the photograph. On heating a metallic object above 600°C, it begins to glow—in other words, to emit energy in the visible spectrum. With increase in temperature, the energy of the radiation increases, and its spectral composition changes. This is accompanied by increase in brightness and change in color of the radiating object from red to yellow and then to white. This radiation may be recorded using a digital camera and converted to a file (in graphical format) for subsequent computer analysis. In the digital data, change in luminance of the metal is accompanied by subsequent increase in the red, green, and blue components. The parameters of the photo recording greatly influ ence the resulting values of the color components. Each camera has a particular set of optical elements, charge coupled matrices, and systems for output-signal analy sis. Consequently, the transfer characteristic of each camera model will be distinctive. Therefore, the camera must be calibrated so as to adjust its color profile and standardize the output parameters. Various standard test scales are used for calibration. In the present work, we employ the Macbeth Color Checker scale.