All off-street parking areas for nonresidential uses in nonresidential district which are used after dark, shall be illuminated beginning one-half hour after sunset and continuing throughout the hours of use or until midnight, whichever is earlier. In case only a portion of a parking area is offered for use after dark, only that part is required to be illuminated in accordance with these standards. However, the portion offered for use shall be clearly designated. Lighting within the parking areas shall meet the following minimum requirements. No intermittent or flashing lights are permitted.