Throughout his career Steven Spielberg has proved that when it comes to popcorn thrills and light-hearted entertainment, there is almost no-one better on the planet. But when he turns his hand to more serious subject matter, he has a habit of pulling his punches for the sake of a sentimental cop-out, betraying an audience’s trust so that he can make us cry. That is the central problem with The Colour Purple.

Spielberg does not seem like a natural choice for this feminist tale of oppression and humiliation in 20th century Georgia. This is especially the case when you look at his previous film, Indiana Jones and the Temple of Doom. Sure, Indiana Jones is the upmarket equivalent of a B-movie matinee idol, and hence women’s rights are not high up on the agenda. But at least both the other Indy films had the sense and decency to pair him with a strong-willed female character, rather than a damsel-in-distress.

To give Spielberg credit, the first half of The Colour Purple is very, very good. Danny Glover gives a powerful performance as ‘Mister’ (Albert), reminding you that beneath the Lethal Weapon exterior lies a talented and underrated leading man. Whoopi Goldberg, who was Oscar-nominated for her performance, is a great match for him. Every single act of oppression that Mister heaps on Celie is completely believable, and as Celie retreats further inwards your heart goes out to her. You genuinely sympathise with the character rather than simply feeling as if you should: there is great depth to Goldberg’s performance, and in the shaving scenes you could cut the tension with… well, a razor.

The art direction and cinematography are also great, really taking the audience into the heart of black culture. From the tumble-down state of Mister’s house to the juke joint on the riverbank, the sets seem to have been lifted straight out of the 1920s and 1930s. The bleak mood created by these harsh and simple surroundings further enhance the sense of despair at the heart of the story. These are people with not much to hope for, few prospects and little to cling to save their families and strict moral principles, however distorted and corrupted both things may be. Much like the opening of Saving Private Ryan, the audience feel like they are in the characters’ personal hell. It’s a strange sensation, one which is simultaneously frightening and captivating.

But sadly, like so many of Spielberg’s films, it isn’t long before The Colour Purple collapses into a soggy pit of sentimentality, never to emerge. The second that Celie discovers the backlog of letters from her long-lost sister, the film falls apart and never recovers.

This may be a problem with the novel: it is never made clear why Mister kept the letters, rather than simply burning them and thereby permanently destroying Celie’s hope. As far as the film is concerned, this is a deus ex machina, a get-out-of-jail-free card for the director. The discovery of the letters confirms and restores Celie’s sense of hope, and allows her to stand up to her oppressors with seemingly minimal effort in the transition. This easy road to recovery cheapens the message of the film, removing the threat of retaliation and making the whole thing seem rather frivolous. There’s nothing wrong with the idea that hope overcomes all despair, but the film hasn’t earned the right to wave away the problem, at least not so flippantly.

All of which begs the question: if the survival of Nettie is assured, why does the film need to drag out for another hour-and-a-half? Spielberg himself doesn’t seem to know the answer, as long sections of the second half are crammed full of inconsequential rubbish. Why do we need the goofy comedy sequence in which Sophia’s ditzy mistress is learning to drive? Why do we need the scene of the juke band entering the church, which seems to have escaped from 1941? And why, oh why, do we need the sequence of Sophia and Harpo trying on pants?!

The only explanation for this is that Spielberg emphasises them to illustrate Celie’s gradual return to happiness. But as it is, these sequences only emphasise the lack of backbone in the second half of the film. Where the opening act or two was bleak and portentous, and almost as good as The Shawshank Redemption, the latter acts are shallow and inconsequential. Even when Celie and Nettie are united and the tears start rolling, you’re cross with yourself for crying because you know the film hasn’t done enough to make the tears seem genuine.

The Colour Purple stands alongside Schindler’s List and Saving Private Ryan as one of Spielberg’s admirable failures. Each of these films have great opening acts which feel genuine, are inhabited by truthful characters and look fantastic. But each of these falls down on their inability to develop a dark storyline without resorting to over-the-top villains or unjustified special effects. The Colour Purple is not an awful film; certainly it gets away with what it does for a whole lot longer than Schindler or Ryan. It’s just a real shame that Spielberg couldn’t follow through on the promise of the first half and deliver a film about hope which wasn’t cheatingly sentimental. That is the great success of Shawshank, to which The Colour Purple cannot hold a candle.