Make-up brand Smashbox is the choice of Hollywood insiders. Harriet Walker meets its founder to see if it works for real life too

In a downtown studio near Manhattan's West Side Highway, Davis Factor is holding court.

New York's beauty editors, the doyennes of the US fashion industry, even their pre-school children are crowding in, desperate for the chance to have their picture taken by the man who can make women look flawless.

A photographer by day, Factor, 51, is one half of the fraternal duo that runs the cult LA make-up brand Smashbox. Perfection is his métier: fine lines, shine, uneven skin tone, the minuscule facial crenulations of everyday wear and tear, from pollution to smiling, are just some examples of the oh-so-human unsightliness that his products and portraits seek to erase. Factor is spearheading a new movement in High Definition beauty to help women battle the glare of ever-more-intrusive cameras, be they on a movie set, at a wedding or simply on a friend's phone.

"Ten, 20 years ago, people didn't even know what megapixels were," he says between sittings. "We're creating make-up as times change. I created it myself – because my digital camera started to become more and more clear, and I had to retouch stuff more and more. It wasn't like making-people-thin retouching, it was making skin clearer. I could actually see the make-up sitting on the skin."

His keen interest in on-screen beauty is hardly coincidental – Factor and his brother, Dean, 44, are the great-grandsons of Max, make-up guru to the stars during Hollywood's golden age, who is still posthumously known for his eponymous mega-brand. Max Factor was a Russian immigrant who arrived in California at the turn of the 20th century, having previously worked as a cosmetician for the Imperial Russian Grand Opera. Stage "make-up" (Max Factor himself invented the phrase, insisting it be hyphenated) at this time consisted of whatever actors could lay their hands on – Vaseline mixed with flour, paprika and cold cream, brick dust and lard, all applied an eighth of an inch thick – which, despite cracking whenever an actor changed expression, just about worked for long-distance theatrical work.

But for the new movie stars, with their Cecil B DeMille close-ups, something more refined was needed. Max Factor engineered lightweight and light-reflecting potions that made screen icons look their best. He created the "bee-stung" lip by applying lipstick with his thumbs; Joan Crawford's signature smeared lip was his idea, too. As well as sweat-proof body make-up, Max Factor also made the faux-glow perspiration used in Ben Hur, from gallons of water and mineral oil. "The thing about inventing is that it usually comes from a reason," Davis Factor says. "What my great-grandfather did was invent make-up you could wear on Broadway or in silent movies or motion pictures, because what they were using wasn't right. He invented make-up out of the need for make-up that would look better, and we did the same thing, too."

Factor was something of a club kid in his youth, one of many young socialites that populate LA's affluent surrounding hills, and he enjoyed a brief career as a professional skier. But photography was always a passion and he set up Smashbox Studios, with Dean ("He's the brains," Factor tells me over dinner. "I was the photographer.") in 1990, where he has worked with the likes of Jennifer Lopez and Cameron Diaz. Initially a shoot-space for commercial and editorial work, the studio soon became one of the main venues for shows at the fledgling LA Fashion Week, too.

"We have the weight of Hollywood behind us," Factor says. "We have the knowledge of the photography and motion-picture business, too, and we're very make-up artist friendly – we like educating, we don't have a lot of attitude, we're friendly."

All this combines in a cosmetics line that has taken the world by storm since its launch in 1996. Previously known mainly in the United States (Americans have always been better at "flawless" than us Brits), Smashbox has had a successful global creep since it was bought by beauty titan Estée Lauder last year. "Our brand is LA, it's never leaving LA," Factor says firmly, when the sale comes up. "It's what we are."

It's also where much of the beauty industry is focused right now, of course, with more attention being paid to the grooming rituals of celebrities and red-carpet regimens. Since the Oscars were first broadcast in HD back in 2003, stars have been more and more conscious of the need to conceal all possible flaws.

"We were the first brand to come out with HD make-up," Factor says. "And a lot of people said 'oh, they're just making it up', but our products also test better than any other HD make-up. You see make-up more now, so we had to come out with a foundation that was lighter and with good coverage, but that didn't show up at all."

Smashbox's products are impeccably targeted not only at models on set or celebs at a junket but also at the woman in the street. We might not be appearing on telly any time soon, but that's not to say we're not looking for the same sort of hard-wearing durability, coverage and steadfastness in our slap. Smashbox has successfully brought several niche products out of the professional sphere and into the make-up bags of the masses. The Photo-Finish Primer, for example, which goes on before foundation so that it will "cling" to your skin and eliminate shine; or the Eye-Beam Liner, a double-ended pencil that lightens the corner of the eye, as well as the lower rim. These may sound like products for obsessive compulsives, but it's surprising what a difference they make. In fact, they're eminently practical – quick, easy and versatile.

"The cosmetics come from the studio," Factor says. "It's where I test everything, so I'm able to come up with problem-solving solutions as we're making them. It's the perfect place to create make-up – we create everything from super-natural to super-edgy. We try to create a lot of different looks because, as a woman, you want to create a lot of different looks yourself."

It chimes well with the more professional feel to make-up right now, with customers wanting well-considered products that will enhance what they have, rather than redrawing their visage. Despite its HD USP, Smashbox make-up can be dressed up and down; it works just as well for nude and naturally flawless styles as it does for full-on glamour. Factor has it right when he speaks of "solutions" – Smashbox has done all the fiddly work, so that you don't have to.

Another signature product is the Halo Hydrating Powder – a lightweight mineral powder that boosts radiance and reduces fine lines. It contains pure gold and goji berries which provide antioxidants, and glides perfectly on to bare skin for those who want a little help, rather than a lot of foundation. It also comes in a bright yellow colour, initially off-putting but perfect for evening out skin tone – and a nice echo of the yellow foundation that Max Factor created for Rudolph Valentino, to help him break free of being typecast as a swarthy villain.

My final question to Factor is whether he's concerned that flawlessness can be bland, whether perfect people are boring. "I'm jealous of those people!" he says. "Sometimes you see someone who looks so flawless and you're like, 'man, I have to get a facial once a month'. We'll help someone look flawless though – and when you make a claim, it has to be real. If it's not real, women know and they complain, and that's the end of that."