It is not normal for Screen to focus on the performance of a specific film but the heroic efforts of Warner Bros' 300 in boosting a year's box office that was already shaping up to be a classic deserves analysis.

It is not the quality of the film that is the big talking point. It is, as many critics have pointed out, a ludicrously loud, reactionary, gory piece of style over substance - but it has some bad points, too.

300's success in most territories offers a welcome and unexpected turbo boost before Easter and the most promising looking summer in recent memory. The effect of one big performer this month is an encouraging reminder of the real scale of the task for the theatrical business.

Most other industries do not see their fortunes rise and fall on the performance of such a relatively small amount of product. We are back to Samuel Goldwyn's line that there is nothing wrong with the picture business that one good picture can't fix.

What cinema needs is not a huge socio-economic shift, a reorganisation of national education systems or a gadget to unlock its potential. In most countries it just needs people to go to the movies one more time a year. The manic leap between end-of-the-world depression at the end of 2005 to the elation of 2006 comes down to small shifts.

The second important point to make is about technology. What makes 300 important is that it looks like a blockbuster and it feels like a blockbuster - but it cost a great deal less.

That is not an argument for a green-screen future - the most depressing thing about 300's success is the stream of hopeless, geeky copycat movies that will inevitably follow. But digital techniques have been able to reduce costs without destroying the dramatic effect. One thing you cannot accuse Zack Snyder's film of is being under-sized.

At least understanding how digital technology can reduce costs is surely now a duty for all film-makers.

The last point to highlight is that 300 is a bona fide surprise: it was not expected by investors, critics or commentators.

Judging by the consumer marketing, which in many territories is referencing the much smaller Sin City, it is a happy surprise even for the distributors.

Cinema loses its impact if there is too much reliance on formulae; there is sometimes a whiff of complacency in some of the remakes and sequels around. That also applies to the independent sector, particularly in Europe, where one hears much more about companies seeking to make "commercial" or "genre" films - pointedly drawing a line between such fare and arthouse film.

What the customer wants is an 18th century costume box and a coach-and-four on crunchy gravel... or a flesh-eating aardvark awoken by global warming on the Scottish moors, they say.

What 300 suggests is that what the customer wants is decided by the customer. To complicate matters, the last person to know what he or she really wants is the customer.

The market research people did not come to the office one day, saying: "You know what the public want: a homoerotic comic-book history lesson with rhinos - and go easy on the star power."

Having a sense of a potential audience is vital to today's film for setting a budget or marketing strategies. But that is not an argument for formulaic cinema but for maximising the potential for a product to get seen, and that is as big an issue for experimental arthouse as it is for the blockbuster.

300 shows off one of the theatre's greatest assets, the power of the unexpected. Its success wonderfully demonstrates the benefits of a bold gamble and, of course, plain good luck.