Our prey is a teeny slip of a thing in a sleeveless green T-shirt, cutoff jeans and saucer-sized shades. We spot her wedging a giant Mercedes into a parking spot on one of the ritziest streets in Beverly Hills. The photographer cruising down Canon Drive slams on the brakes and, with tires screeching, executes a well-practiced U-turn.

“Yes, yes, that’s her,” he says, drawing level with the diminutive figure. “I recognize the yellow hair extensions. I was there when she had them put in. Her dog’s got them, too.”

It is 1:30 on a warm October afternoon and Jeff Rayner, a Hollywood paparazzo, is out trawling for stars. He just got lucky: Nicole Richie, daughter of soul singer Lionel and subject of the television reality show “The Simple Life,” is meeting the hotel heiress Nikki Hilton at La Scala, a swish eatery a few blocks east of Rodeo Drive.

Mr. Rayner, a British-born “celebrity photographer” based in Los Angeles for six years, hauls his BMW SUV round a corner and pulls up in a no parking zone opposite the restaurant. Mlles. Richie and Hilton are, thankfully, seated outside, nattering into chunky silver cell phones.

Mr. Rayner winds down a heavily tinted window and slaps a vast 300 mm lens onto his digital Nikon. He fires off half a dozen frames, checks the quality and aims again. Despite the fact that his targets are under an awning, 100 yards away, the pictures are crystal-clear.

It is a scene replicated on the streets of Los Angeles every day, where celebrities and paparazzi play cat and mouse in Hollywood’s human zoo, chasing up and down its famous strips and into the hills, Bel Air, and beyond.

To many, paparazzi – named after Paparazzo, the photographer in Fellini’s La Dolce Vita – is a dirty word, synonymous with harassment and forever linked to the death of Diana, princess of Wales, whose car was being pursued by photographers when it crashed in a Paris underpass.

But to those who make their living from photographing the famous (and it can be exceptionally lucrative), the celebrity is essentially a public figure who courts exposure and is often complicit when photographed – or “hosed down,” as the terminology goes.

As Janice Min, editor-in-chief of gossip magazine US Weekly, puts it: “A celebrity is like an elected official. If you’re getting paid $20 million a movie, you have to rely on public goodwill to stay in office. You have to accept the fact that you’re a public commodity.”

There is no such ambiguity in “Paparazzi,” a new film from Mel Gibson’s Icon Productions, an excoriating depiction of the profession in which a group of ruthless photographers cause a Diana-style crash.

The crudely drawn revenge fantasy, which was recently released, focuses on four paparazzi – unshaven, amoral “parasites” who proclaim themselves “the last of the real hunters,” as they set about hounding a fictitious A-list actor, Bo Laramie, and his family.

At one point, the pack’s ringleader, a convicted rapist called Rex Harper (played by Tom Sizemore), threatens Laramie: “I’m going to destroy your life and eat your soul. And I can’t wait to do it.”

The snapping point for Laramie – and, possibly, the audience – is when the pap pack, having caused the crash that injures his wife and puts his son in a coma, crowd round the wreckage taking pictures before dashing off to “make some money” from their spoils.

The portrayal has raised the hackles of many in the profession. “It’s pretty sick that he [Mel Gibson] has attempted to recreate the Diana death crash for entertainment,” says Kevin Smith, director of Los Angeles-based Splash News and Pictures.

Luckily for the real-life paparazzi, most celebrities don’t respond as violently as Laramie to having his privacy invaded, and embark on a killing spree, but the film seems to suggest that many in Hollywood have had enough of the men with the long lenses. Gwyneth Paltrow declared last month that she is going to start pressing charges against photographers who go to great lengths to take her picture.

“They chase you in cars, and they’re endangering me by the way they drive,” she said. “It’s just unacceptable, especially when there’s a life of a small baby in your hands.”

Mr. Rayner, 30, defends his profession with a breezy self-confidence. He says he’s glad the film is so “far-fetched because people won’t take it seriously.” But the former head boy has his doubts about the way he makes his living.

“I look at my friends back home – getting married, getting mortgages, having babies – and here am I, hosing down Britney on Sunset. The trouble is, it’s just so lucrative.” He can earn around $25,000 for a set of pictures – “Not bad for 20 minutes’ work.”

The aim is to get shots that tell a story: “Basically, anything that could spark a rumor or be a little bit cheeky.”

Mr. Rayner’s armory of tricks includes driving the same make of SUV that many stars favor so that he can blend in, slipping into awards ceremonies with a tiny camera hidden in a mint tin to fool security’s metal detectors, and walking into hotels where a celebrity is staying while gabbling into his phone to reduce the chance of being challenged. He also has a book in which he records stars’ addresses and license plates – “a stalker’s dream,” he calls it.

Mr. Rayner has to be canny. Working alone, exclusivity is key and on the congested streets of Los Angeles, competition is fiercer than ever.

About 100 paparazzi vie for jobs, many working for agencies such as Splash, Bauer-Griffin (“the Hollywood Hunt Club” according to its Web site), X17, WireImage, and Fame Pictures. All are desperate to cash in on society’s unquenchable thirst for celebrity, with some prepared to go to any length to get the shot that will fetch a small fortune from the gossip magazine market.

“It’s fierce, absolutely ridiculous,” says Giles Harrison, 36, who has been a paparazzo in Hollywood for 10 years. “Every idiot thinks he can pick up a digital camera, bang off some pictures and make 20 or 30 grand.”

“The new guys go storming in and start chasing celebrities at high speeds,” says Gary Morgan, co-founder of Splash. “They are not trained photographers and make money only if they get a picture. That’s what’s causing the problem. It’s turned into a zoo.”

Nevertheless, he defends the job: “There’s a relationship between us and celebrities. They don’t want us around, but they know they need the publicity. They see us as a necessary evil.”

A paparazzo’s job tends to involve “trawling” and “door stepping,” where photographers sit outside a star’s home “peeing into a bottle and praying they’ll emerge,” as one puts it.

The day before our trawl of the homes of, among others, Ben Affleck, Courtney Cox, and Tobey Maguire, Mr. Rayner had snapped Jennifer Aniston on Sunset Boulevard – a rare find. She and her husband, Brad Pitt, along with fellow A-listers Catherine Zeta Jones and Nicole Kidman, are some of the wariest, most security-conscious stars and, therefore, the most coveted paparazzi targets.

“Jennifer and Brad never go out together,” says Mr. Rayner. “Brad’s even got a camera on his car that shows the license plates of the person behind him, so he can check if someone’s following.”

Stars develop their own way of handling the paparazzi. Mr. Affleck usually attempts to outrun them in his powerful Mercedes, while “fisty” actors, such as Dennis Quaid and Sean Penn, can turn aggressive if pursued.

Mr. Rayner prefers noninvasive tactics, staying in his car wherever possible. Harrison agrees. In 1998, he was jailed for 60 days after a run-in with Arnold Schwarzenegger. He and another photographer were accused of forcing the former actor’s Mercedes, carrying his pregnant wife and son, off the road before jumping out and taking pictures.

“It scared the shit out of me,” Harrison admits. “Now, if people ask me to leave, I will. Basically, if I’m doing my job well, then nobody knows I’ve been anywhere near them until they open the paper.”

Back in Beverly Hills, Ms. Richie has, to Mr. Rayner’s delight, begun shoveling big forkfuls of salad into her mouth. Mr. Rayner fires away and then, satisfied that his subject is “in the bag,” decides to call it a day.(His pictures later appear in teen gossip magazine Sneak, under the caption, “Unladylike eating”).

We head off. Around the corner at some lights, Mr. Rayner checks the profile of the driver in front. “That’s Jeff Goldblum!” he cries, grabbing his book and looking up the license plate. “Yes, it is. I recognized his ears.”

“This job is just like fishing. Sometimes, you go a whole day and get nothing and then, suddenly, bang, you’ll spot three or four in a row.”

Ahead of us, Mr. Goldblum’s jeep bolts away from the lights. Mr. Rayner puts his foot down and gives chase.