If you haven't seen Janet Jackson's new video for ''Love Will Never Do (Without You),'' then you haven't seen Janet Jackson. After years of swaddling herself from nape to toe, Jackson has decided to show herself off. In the clip she wears a low-cut shirt and a pair of scruffy jeans. Unlike her quick, hyper-aerobicized choreography on earlier videos, her moves are gliding, relaxed, and sensual. ''Everyone is surprised it's her,'' says Herb Ritts, who filmed the video. ''In this day and age, it's not that unusual for most people to do this, but it was for Janet.'' Ritts, a well-known still photographer, first shot Jackson earlier this year for Vogue, and he says she has worked hard to get into top shape. But Ritts was less interested in the way Janet looked than in the way she acted: ''She's very shy. But as soon as I got her away from (her entourage), she was flirty and great.''