In an X-ray image intensifier tube an entrance section is optimized in respect of image quality, optical aberrations and efficiency. To achieve this, notably in order to avoid photocathode charging phenomena, a separating layer having an adapted electrical transverse conduction is provided. In order to reduce scattered radiation, an edge portion of the entrance screen is deactivated for relevant examinations. In order to increase efficiency, use is made of a double phosphor layer having different X-ray absorption properties. In order to compensate for vignetting a radial variation of the thickness or of the radiation properties of a separating layer or of the luminescent layer itself is used.