Cynthia B. Sheaff, a 36-year old actress and mother, has sued TV Guide and Westinghouse Broadcasting for the unauthorized use of her photo to advertise a San Francisco TV show about strippers. The $400,000 suit filed in federal court this week claims that the July 12, 1983, TV Guide ad for KPIX's "Evening Magazine" show damaged her career and reputation. In the ad, a photo of Sheaff appeared with the caption: "Take it off! Catch a glimpse of the world's most successful strippers strutting their stuff at the First International Striptease Convention in Las Vegas." Sheaff said the same photo was taken in 1981 for a TV Guide ad plugging another "Evening Magazine" segment where she was depicted as a Hollywood starlet. An attorney for Westinghouse argued that KPIX received verbal consent from Sheaff's modeling agency to use her photo.