Identical twins Martha Williams and Mary Heater were best friends while growing up in Elmhurst. But things began to change in high school. “There was a point where we needed to have different friends,” says Martha, who started studying photography around that time as part of an effort to “be my own person.”

After graduation the pair went their separate ways–Mary to Illinois State University for biology and Martha to College of DuPage and then Columbia College for photography. But “even though we wanted to be different, we were unconsciously doing the same things,” says Martha, who’s 24 and has just graduated. “[Mary] would call and say, ‘I dyed my hair and cut it,’ and I had done the exact same thing. She’d call to say she’d had her nose pierced, and I’d done it too.”

Things changed again four years ago when Mary–then a junior in college–got married, moved back to the suburbs, and gave birth to a baby girl. Martha started spending more time with her sister, but at that point she hadn’t considered photographing her, “Probably because I was still wanting to have my own identity.”

The pair were named for the Bible story about two sisters who are visited by Jesus; Mary sat at his feet and listened to what he had to say, while Martha cooked and waited on him, and was chided for being worried and distracted.

“Our parents lived in a religious community and the leader named us,” says Martha. (The family quit the group when the twins were five.) “She said to name the first twin Mary because she’s supposed to represent the spiritual world. I was supposed to be more interested in achieving things in the material world.

“I don’t know if it’s true because of that, but it’s definitely true,” she continues. “I think she’s always been more concerned with those areas in life. Experiencing motherhood is a spiritual and gratifying experience for her, although it wasn’t planned that way. Mary actually finished school before I did, after having a child.”

When Mary’s daughter Satya was two Martha decided to start a photography project based on their different paths. “Seeing how different our lives had become made me interested in exploring her life and my life and how different they are, rather than how freakishly similar they were,” she says.

One of the more dramatic photos in Martha’s new exhibit, “Mary & Me,” shows Mary sitting in her laundry room, dwarfed by piles of dirty clothes, her head framed by the dryer behind her. (“I have trouble keeping up with the laundry,” explains Mary, who had her second child last year.) A companion photograph is dominated by Martha in a bra sitting at the edge of her bed, facing the camera. A man is sleeping in the background, and there are empty beer cans on the floor. “Not that that’s how I live all of the time,” she says, “but it’s an example of how things can be.”

In another photograph the sisters sit side by side in front of Mary’s duplex in Lombard, separated by an iron railing. Mary is smiling, Satya on her lap and a neighbor’s child at her feet, while Martha looks away. “When I first started taking pictures of her, it made me uncomfortable, because I had wanted it to be my own thing,” says Martha. Now she thinks of her sister as a collaborator. She describes the scenes she shoots as “totally constructed,” but not posed, since they’re taken from real events.

“Sometimes I’ll walk in on my sister doing laundry and I’ll say, ‘Stop. Stay there.’ I’ve already altered the situation. So I guess it’s more about experiencing an idea or capturing a moment. They’re idealized or symbolic moments.”

“I like it,” says Mary. “It’s kind of a vain thing. Everybody likes having their picture taken.”

“Not me,” says Martha. “Not unless I’m taking it.”

“Mary & Me” opens Monday, June 24, and runs through August 2 at Columbia College’s Hokin Annex, 623 S. Wabash (312-344-7188). Gallery hours are 10-5 Monday through Friday, and the sisters will be at the free opening reception on Friday, June 28, which runs from 6 to 8 PM.