On a warm summer afternoon in 2005, Bryant Austin was snorkeling in the blue waters of the South Pacific by the islands of Tonga, looking through his camera at a humpback whale and her calf swimming less than 50 yards away. As he waited for the right moment, the playful calf swam right up to him, so close that he had to lower his camera. That's when he felt a gentle tap on his shoulder.

Turning around, Mr. Austin found himself looking straight into the eye of the mother whale, her body bigger than a school bus. The tap had come from her pectoral fin, weighing more than a ton. To Mr. Austin, her gesture was an unmistakable warning that he had gotten too close to the calf. And yet, the mother whale had extended her fin with such precision and grace -- to touch the photographer without hurting him -- that Mr. Austin was in awe of her ''delicate restraint.''

Looking into the whale's eye, lit by sunlight through the water, Austin felt he was getting a glimpse of calmness and intelligence, of the animal's consciousness. The moment changed Mr. Austin's life. It struck him that something was missing from four decades of whale photography: the beauty of true scale. Mr. Austin concluded that the only way to capture the magnificence of whales would be to create life-size pictures of them. ''I wanted to recreate the feeling I had when I looked into the eye of the mother whale,'' he said.

Mr. Austin has since pursued that dream, spending countless hours at sea in the company of whales. Working with five different whales from three species, he has created 25 true-scale pictures, including two full portraits -- each composed from dozens of photographs of different sections of the whale's body. The largest photo is a 6-by-30-foot portrait of a dwarf Minke whale from the Great Barrier Reef in Australia; the panels that make up the image weigh a total of 600 pounds. Some of Mr. Austin's work went on display this month at the Electric Works gallery in San Francisco.

Mr. Austin, founder of a nonprofit organization called Marine Mammal Conservation through the Arts, has exhibited his images Norway, Iceland and Japan, all whaling nations. Although an international moratorium on commercial whaling has been in effect since 1986, these countries and a few others kill several hundred whales every year. Mr. Austin's hope is that his portraits of whales in their life-size splendor will give audiences an emotional connection to these animals, building support to end whaling. He also wishes to raise awareness about the other threats that whales face today, from deaths caused by entanglement in fishing gear to the acidification of oceans caused by global warming.

''The images are unique and true representations of beings so vastly alien to us, yet connected through the mammalian way,'' said Elizabeth Eyre, a whale biologist at Macquarie University in Sydney who has known Mr. Austin for years. ''The sheer size of the portraits alone allows viewers to grasp the discrepancy in dimension between us and them.'' The images are also noteworthy for their remarkable detail. ''Every parasite, scar, flake of peeling skin is visible,'' Ms. Eyre said.

Mr. Austin dropped out of college in the 1990s to take a job at the Institute of Marine Sciences at the University of California, Santa Cruz, where he provided support to researchers studying sea otters. On the side, he began photographing sea otters in the wild. He eventually bought an inflatable boat and started going several miles out to sea in search of whales. He wasn't able to get close enough to whales to take good pictures until one day in 2004 when a whale surfaced near the boat and blew, spraying mist high into the air. Mr. Austin made what he thought were amazing compositions, but was devastated when the film showed nothing. ''I was ready to give up,'' he said.

However, since he'd already bought a nonrefundable ticket for Tonga, Mr. Austin decided to take one last chance at whale photography. After his encounter with the mother whale and its calf, he returned to California to raise money for his newfound mission. Friends and family members chipped in, but foundations turned him down. He sold his car and his trailer. ''It was a leap of faith,'' Mr. Austin said. The money enabled him to return to Tonga for 125 days of fieldwork, during which he successfully composed one life-size portrait of a 12-foot-long calf.

In December 2008, Mr. Austin put that portrait on display in the lobby of a hotel in Santiago, Chile, where the International Whaling Commission was holding its 60th annual meeting. ''I saw a gentleman with his friend admiring the photograph,'' he recalled. When Mr. Austin walked up to them and offered to take their picture with the whale in the background, the person asked Mr. Austin if he was the whale photographer. ''After I said yes, within 30 seconds, the next sentence out of this gentleman's mouth was 'Do you have a budget?'' Mr. Austin said.

The man was Peter Hall, the chairman of an Australian investment management company and part-owner of Prospect and Monocle magazines. He contributed enough money for Mr. Austin to acquire a new Hasselblad 50-megapixel camera along with the equipment to operate it underwater, and for five weeks of fieldwork. In January 2009, Mr. Austin was off to the Caribbean island of Dominica to find a pod of sperm whales he'd heard about from whale biologists.

The search tested Mr. Austin's will, and five weeks went by without success. ''I called my mother and said, 'There's nothing, I'm coming home,'' he said. ''She was crying.'' On the water the next day, Mr. Austin got a radio message from Shane Gero, a whale researcher at Dalhousie University in Nova Scotia who was doing fieldwork in the area. Mr. Gero had seen a family of sperm whales known to scientists as the Group of Seven.

When Mr. Austin got close to the site and slipped into the water, bobbing on the surface, a big female swam right by him and dived down to the depths. Her 2-year-old calf, named Enigma by whale biologists, started swimming around him. For the next 45 minutes, Mr. Austin -- who uses a scuba mask to stay 3 to 4 feet underwater while taking pictures -- took dozens of photographs of the calf's eye, head and body, which he later patched together into a full-body composite.

''When I went back to my boat to change batteries, he followed me,'' Mr. Austin said. Later that day, Mr. Austin was able to take some pictures of Enigma's 11-year-old brother, Scar, an inquisitive adolescent who at one point approached as close as 10 feet with his mouth open. Mr. Austin has no doubt that the whales were studying him as much as he was studying them.

Based on his experiences and tips from whale biologists, Mr. Austin has learned to follow certain protocols to maximize his chances of success. He doesn't take his boat closer than 10 feet to a whale, preferring instead to float in the water and let the animal swim up to him.

''Everything about my work with them is predictable,'' he said. He uses the same vessel every day, and approaches the whales' site at a slow and steady two knots, avoiding any changes in speed. ''You want them to get to know you,'' he said. ''The idea is to gain their curiosity.''

At an exhibition in Tokyo last December, Mr. Austin's portraits evoked curiosity and praise, generating the emotional response that the photographer hopes to stir in his audiences, said Kotoe Sasamori, a Japanese naturalist and whale-watching guide who helped organize the event.

Viewers commented on the beautiful, calm expressions of the animals, and the feeling of being watched by the whales. ''I saw some people crying,'' Ms. Sasamori said, recalling one viewer's remark: ''I feel like the whales are talking to me with their eyes.''

PHOTOS: EYE-CATCHING: Bryant Austin's ''Dwarf Minke Whale Portrait 1186'' is a life-size work from the Great Barrier Reef. (D1); FLOATER: ''Studio Cosmos, Kingdom of Tonga'' by Bryant Austin, who doesn't take his boat within 10 feet of a whale, preferring to let it swim closer. (PHOTOGRAPH BY BRYANT AUSTIN)(D2)