An X-ray examination apparatus includes an X-ray image intensifier for deriving an optical image from an X-ray image. The optical image is picked up by means of an image pick-up apparatus which includes a correction unit which is arranged to form a dark image signal and to derive test image signals from the optical image. Correction values are derived on the basis of the test image signals and the dark image signal. The correction unit is arranged to form a dark image signal, to derive one or more test image signals from the optical image, and to derive the correction values from said test image signals and the dark image signal. The dark image signal is picked up in the absence of incident light on the image sensor. The test image signals have a signal level which represents brightness values of the optical image which have been amplified by individual gain values.