1. A method for positioning a level of a slice of an X-ray exposure to be generated by irradiating a subject in an examination direction, said method comprising the steps of: obtaining a reference image of an exterior of a subject with a camera along a line of sight transverse to said examination direction; indicating a selected slice level with a marking in said reference image; and using said marking in said reference image to set a slice level when irradiating the subject with X-rays with an X-ray examination device.