Applying of pixels separation brightness threshold is usually used to find the object boundaries. It is proposed to use a method for dividing the brightness of pixels to assign them to one of the zones of the fuel jet. A low brightness area with higher concentration of fuel, and vice versa, a zone with sufficient brightness (except the background luminance) has a lower concentration. Studying the dynamics of the change in brightness in the zones of a jet, we can talk about the quality of fuel atomization nozzles that can be different under different conditions.