The appts. is used in laboratory investigations of fast moving objects. In order to obtain well defined images the charging time of the individual capacitors forming the signal plate (3) is restricted to a fraction of the line scan and reset time for the plate. The relationship between these times has to be precisely defined. With the proposed timing alteration standard cameras and video receiving apparatus can be used. Typically either the illumination time of the photo-cathode (2) or the illumination time of the object to be recorded is limited to the desired integrating time interval for the signal plate (3) capacitors. The timing may be achieved by a shutter (5), flash illumination of the object, or electronically from inside the camera. Whichever method is used it must be synchronised to the line scanner. Either conventional or CCD cameras can be employed.