MOST OF THE 75 photographs in "To Protect and Serve: The LAPD Archives," selected from the hundreds of thousands in the Los Angeles Police Department archives, show the aftermath of crimes or detectives at work. They are far more interesting, however, as period pieces. If we didn't know they had been taken in the line of duty, we might mistake them for Hollywood film stills from Dragnet or L.A. Confidential. It's remarkable how many photos recall the staging, lighting, and costumes of vintage film noir, which makes one wonder whether those old films were remarkable for their vérité or whether LAPD photographers at that time were influenced, consciously or unconsciously, by the movies they watched during their off-hours. Issues like this point to other, more complicated questions regarding artistic intentionality. Clearly most of the photographers never expected their work to be viewed as art – if they had considered themselves artists, they probably wouldn't have been very good police photographers – but the exhibit's curators deliberately downplay the documentary aspect of their work. On some walls, as many as eight prints are arranged in long rows with just a single wall label all the way at the end, effectively preventing textual clues like titles and descriptions from directing our viewing experience. The strategy is a provocative one, and it succeeds in drawing attention to moments of haunting beauty (Bridge over L.A. River, 1955) or unintended Keystone Kops humor (Bootleg Raid, 1929). But it can be a little frustrating, too, especially when there's obviously a good story behind a particular image. The exhibition also features only a handful of interesting police photos from the Black Dahlia murder and other famous cases; it would have been fun to see more of these and fewer anonymous corpses. Tues.-Sun., 11 a.m.-5 p.m., 701 Mission, S.F. $6, $3 students and seniors, free for members (free first Tuesday). (415) 978-ARTS. (Lindsey Westbrook)