For Vanity Fair's annual ­Hollywood issue a few years back, photographer Annie Leibovitz created a classic image of a film director at work. Posing beneath a stormy sky, George Clooney stood with his shirt ripped open, trousers tucked rakishly into his boots, arms outstretched – a young Orson Welles meets Michelangelo's vision of God. His crew were a crowd of female models in flesh-coloured lingerie; not the obvious costume for a camera operator, but there you are. This was the auteur as masculine genius, a warrior amid a sea of passive women.

This has long been the archetype of the film director, but over the last few months a host of women have been making waves: Sam Taylor-Wood with Nowhere Boy, Lone Scherfig with An Education, Andrea Arnold with Fish Tank. Then there are Kathryn Bigelow and Jane Campion, both trailing Oscar buzz for The Hurt Locker and Bright Star respectively.

So, is this a new era for female film-makers? Unfortunately, the numbers suggest otherwise. In a study published last year, Professor Martha Lauzen of San Diego State University found that only 9% of Hollywood directors in 2008 were women – the same figure she had recorded in 1998. If Bigelow is nominated for the best directing Oscar in March, it will be only the fourth time a woman has been nominated, out of more than 400 director nominations altogether (the other three were Lina Wertmüller in 1976, Jane Campion in 1993, and Sofia Coppola in 2003). No woman has ever won. No wonder, then, that last year Campion entreated ­aspiring female directors to "put on their coats of armour and get going".