An x-ray diagnostic installation has a high-voltage generator, an x-ray tube supplied by the high-voltage generator, and a solid-state image converter on which x-rays, attenuated by an examination subject disposed between the x-ray tube and the solid-state image converter, are incident. A control unit is connected to the high-voltage generator and to the solid-state image converter, and controls the high-voltage generator to cause the x-ray tube to emit a first x-ray pulse of a short duration which produces an x-ray exposure in the solid-state image converter. The control unit conducts a read out of the solid-state image converter to obtain a measured value representative of the x-ray dose rate, the control unit using this measured value to calculate the x-ray transparency of the examination subject and, from the x-ray transparency, to calculate an optimum x-ray dose. The control unit then operates the high-voltage generator to cause the x-ray tube to emit a second x-ray pulse, having the optimum x-ray dose, for acquiring a diagnostic image of the examination subject.