(Correction: Because of a reporting error, the surname of one of the photographers whose work appears in the exhibition ''Document" at the Photographic Resource Center at Boston University was misspelled in a review in Sunday's Arts & Entertainment section. Her name is Amber Davis Tourlentes.)
A photograph may or may not be art. It's always information.
Before it does anything else, a picture shows something. It can do many other things, too -- dazzle or provoke or arouse, you name it -- but any other visual action is subsequent to the presentation of information.
This primacy of showing underlies ''Document: Contemporary Social Documentary Work From Greater Boston," which runs at the Photographic Resource Center through March 26. Chris Churchill, one of nine photographers in the show, puts it best in an artist's statement. ''To find truth in photography we must understand that the medium can reflect aesthetic choices on the part of the photographer, but at its heart, it is representational."
What's represented here are eight local communities, communities variously defined by vocation, location, and circumstance. (There are only eight because two of the photographers, Mariliana Arvelo and James Patten, are collaborators, as well as husband and wife.)
Arvelo and Patten's subjects are deaf and blind. Arvelo takes color photographs notable for their warmth and matter-of-fact humanity. She doesn't beseech or strain for emotional effects. She doesn't have to. The liveliness of the play of hands she captures as language is being signed in '' 'Untitled,' Newton, MA" is a marvel of expressivity. ''Play of hands" is the essence of Patten's work: He uses a laser to etch tactile equivalents of Arvelo's images. His hang below hers, with a sign bearing the memorable notice ''Please touch! But do not lean."
Sometimes community is a function of place, as with Churchill's photographs of the students and faculty at the Patrick O'Hearn Elementary School in Dorchester, or Suzi Camarata's images of merchants and their stores in Mission Hill. Yet as their work reminds us, the more specific the place, often the more universal the effect. Who among us hasn't gone to grade school? Who among us wouldn't want to entrust his rugs to an affable employee of ''Joseph Sullivan Carpet Cleaning"?
Sometimes community is a function of vocation -- and, it turns out, age. Claire Beckett's subjects, National Guard personnel, and Surendra Lawoti's, Somerville firefighters, both wear uniforms and do dangerous jobs. What's striking about Beckett's people is how young they are. It's as if their uniforms are wearing them. Conversely, Lawoti's sitters are older, more seasoned, fully emerged. She takes big color portraits, 40 inches by 32 inches, and the faces of these men are worthy of such imposing scrutiny. Lawoti's camera looks them in the eye, and they look right back.
Looking into the camera can be a social or even political statement. That's the case with the 42 snapshot-size color pictures that make up Amber Davis Tourientes's big photo mural ''Families on Stage." Each image shows a same-sex couple and their children. Like any family photo, the pictures are full of affection and warmth. Also, like any family photo, they're about people rather than statements. Tolstoy never imagined same-sex marriage, but Tourientes's pictures bear out that all happy families really are alike.
''Families on Stage" affirms and celebrates its subjects. Only affirmation is in order for Michael Manning's images of local homeless people and Lisa Kessler's photo project ''Heart in the Wound," about the church sexual-abuse scandal. Both Manning and Kessler, who shot their subjects in black and white, offer a strong sense of narrative. Even with just fleeting glimpses, we sense a context for these lives.
Sometimes Kessler spills over into tendentiousness. Her motivation is understandable -- perhaps unavoidable -- but it produces uneven results. The heavy-handedness of the looming image in ''Video Projection of Cardinal Law Saying Mass for 3000, Boston, MA, March 2002" contrasts unfavorably with the grim eloquence of the empty office space in ''Director Barbara Thorp Moving Into the Newly Created Archdiocesan Office of Healing and Assistance, Newton, MA, June 2002."
''Document" has an extensive online component, at www.bu.edu/prc/document/links.htm, with more than 90 links relating to the photographers' work and subject matter. A document, after all, can consist of pixels on a screen just as it can an image or piece of paper.
Mark Feeney can be reached at email@example.com.