Neighbors, friends and teachers were dropping hints — some subtle, others pointed, even cruel — that something was not right with Timothy Archibald’s first child, Elijah.

The little boy seemed hypnotized for hours by certain objects: doors, mechanical gears, the vacuum cleaner hose. He mimicked electrical sounds, knew the time schedule of the Bay Area Rapid Transit system by heart and had epic tantrums. Mr. Archibald, 43, an editorial and advertising photographer whose commercial clients include a maker of artificial limbs and Skittles candy, remembers thinking, “I can’t raise this kid; I can’t relate to him at all.’’

The tension at home was all but unbearable. Every waking hour had to do with Eli, who was 5 at the time. Why was he this way? Why was he that way? Was he mentally ill? Should he be medicated? In retrospect, the evidence seems so unambiguous, particularly once there was a second child, Wilson, to compare Eli to. But nobody in the household had yet spoken aloud the word “autism.’’

That was the moment when Mr. Archibald decided to look for his son, in the most literal sense of the word — through the lens of his camera.

“My feeling of utter frustration and powerless started this project,’’ he said recently about “Echolilia,” a limited-edition volume with 43 photographs, mostly of Eli. (It was published in June by Echo Press.) The title is derived from echolalia, a technical term for the copying of sounds and sentences common in children who suffer from some form of autism, who include verbal children like Eli who attend regular public schools. “I knew he was tuned differently,” Mr. Archibald said, “and I needed to build a bridge, get inside his head, learn what made him tick.’’

This would not be a standard documentary project in which he turned his camera on the boy at any and every opportunity, to chronicle his life. Nor would he stage and shoot standard portraits.

Instead, man and boy, father and son, would collaborate, in formal shooting sessions that rarely lasted more than 5 or 10 minutes but were regularly scheduled and initiated by an object or notion that interested Eli. It was Eli’s idea to see if a very large manila envelope would fit over his head; Eli’s idea to blow into one end of a vacuum cleaner hose and hold the other end to his ear to hear the whoosh. It was Eli’s idea to see if he could curl up his body until it fit inside a clear plastic toy box, to flatten his features with a wide rubber band, to look through the wide end of a funnel that happened to be the same circumference as his face. “He has always fetishized objects,’’ Mr. Archibald said. “They are iconic to him.’’

With a digital camera, photographer and subject could examine each image immediately. Sometimes Eli would have an idea for a more interesting pose or setting. Mostly that was Mr. Archibald’s job. He might suggest that they try the shot again at a different time of day or in a place with different light. The collaboration “satisfied something deep inside both of us,” Mr. Archibald said. “We shared — I don’t know what — mutual respect?’’

Light mattered. And simple settings. And contrast. And composition. Take, for instance, the photo of Eli and the vacuum cleaner hose. It was on the living room floor when he came home from school one day because his mother had been cleaning. It riveted the boy. “This is cool,” he told his father. “Let’s make some photos.” First, they went outside, where the light would be better. But Mr. Archibald didn’t like the image of the boy seated, tube to his mouth and ear, amid the chalk scrawling on the driveway. They moved to the backyard. Mr. Archibald noted the dark expanse of dirt and wanted to see Eli’s pale skin against that background. On an impulse, he said, he asked his son to take off his shirt.

One photograph juxtaposes a page of notes Mr. Archibald took when Eli’s ailment was diagnosed with a child’s bandage. It’s meant to capture the specialness of this child, which exists side by side with the fact that he is a normal little boy who skins his knees. “I was looking for that push and pull,’’ Mr. Archibald said, “the flux between the two.’’

All the pictures are set at home, in El Sobrante, Calif., a working-class community in the East Bay, quite charmless with its unlandscaped lawns and commercial strips lined with muffler repair shops and the like. Why only at home? “That’s where the tension was; that’s where I was trying to be a parent and feeling I was doing such a bad job of it,’’ Mr. Archibald said. “This is not about Eli in the world.’’

The world will soon enough impinge, Mr. Archibald fears, when Eli, now 8 and in the third grade, hits middle school. For the moment, “quirkiness is accepted by the other kids,’’ he said. “There is no social big boot to crush him yet.’’ Mr. Archibald said Eli finds nothing embarrassing about the book, despite what he acknowledged might look like “feral” images to some viewers, including a number in which the boy is unclothed. “There is no adolescent body consciousness yet,” Mr. Archibald said.

His wife, Cheri Stalmann, objected to the project at first. She worried that Eli was being exploited to serve her husband’s need to make sense of his own suffering. Eventually, however, Mr. Archibald said she grew enthusiastic as she saw Eli’s pleasure in the work and the results.

When the book was published, the rest of the family celebrated. Eli seemed uninterested at first. Then he asked for his own copy, to keep in his room. There, happily thumbing through it with his father these days, Eli will come upon photos taken as long as three years ago. “Oh, I forgot about that one,’’ he says to his father. “Look how cool it is!”

Written by Jane Gross for The New York Times LENS blog. 10/10/2010