The inarticulate tension that makes Tulsa edgy seems to be absent from later works like his knowingly egregious film, Kids (1995). Whether Clark knew this or merely intuited it, the fact is that there is some kind of internal dialogue going on in his work; an argument between what his pictures are and what they purport to be.This is not to romanticise Clark's work. The pyramidal composition of the woman, her pregnant stomach silhouetted in the glow of an unreadable light source, is a form that has been used to denote maternal purity in everything from Raphael's Madonnas to Whistler's portrait of his mother. Again, it is the formal structure of the picture that introduces the element of moral anxiety. In narrative terms, Tulsa is simply a catalogue of drug-taking, a neutral taxonomy of amphetamine addiction.

The picture's formal qualities tell a different story, though. With her coiffe and her jewellery and her vulnerable breasts, the woman in Clark's photograph is an iconographic type: think of Manet's Olympia.Or look at Clark's picture of a naked pregnant woman injecting herself with amphetamine As a narrative, the picture is morally deadpan. The power of the image lies in the tension between two things. First, there is its narrative form: a story of degradation, of possible sexual threat, but one that is told with no obvious moral voice.

For all their maker's reputation as the high priest of hyper-realism, these are not the creations of some out-of-control speed-freak. Try to deduce Clark from the formal structure of his pictures, and you would end up with a young man who wiped his feet before coming through your door and probably addressed you as Sir. Take his picture of a young woman, carefully beehived and naked but for a choker, lying on an unmade bed while a bearded junkie injects her arm. The curious thing about Clark's photographs is how well-mannered they are. How so? For a work to remain as raw as Tulsa, it must be sensitive to the rules it is breaking: it must be not merely shocking, but potentially shocked. While America comforted itself with the Dick Van Dyke Show, Clark recorded a darker reality at the country's heart. Time and over-familiarity with photographic horror has done nothing to soften the pictures' hard edge. Between 1963 and 1970, Clark took pictures of his Tulsan friends doing the same: damaged adolescents in slummy rooms, with ligatures on their arms and hypodermics in their veins.

In 1959, the 16-year-old tyro photographer started injecting himself with amphetamine. In 1971, Clark published a book of photographs called Tulsa, after his Oklahoman home town. Until Clark, Tulsa had been both literally and metaphorically the heart of Middle America Clark's Tulsa, though, was a different proposition. It seems unlikely that Larry Clark is held in great affection by the tourist office of the State of Oklahoma. Sadly, a couple just isn't enough.C4 Sitcom Festival: Riverside Studios, W6 (0181 237 1075) Wednesday- Saturday. There were plenty of capers, lots of slapstick and a couple of good jokes. Lots of genuine comic possibilities there, then, as well as limitless potential for cheap laughs at all those hippy types, and even a couple of characters who could be decently fleshed out if it was ever commissioned.Which it won't be.

"I was a lesbian myself once, in the Fifties in Kenya." A few more lines like that and it might have worked.Written by Chris Larner, musical director of comedy duo the Right Size (who feature in the Festival this week), Road Rage is about treehouse- dwelling road-protestors. But whereas God's Toilet fizzed and popped with good lines and climactic set-pieces, Welfare's play left one charitably disposed but with sides unsplit."There's nothing wrong with being a lesbian," says Mrs Suddenly, an eccentric villager in Road Rage, the third play. The first line, after much grunting and groaning - on and off-screen - is: "So that's what your ex-wife looks like."Write Back Home also has its quirky characters - a lascivious home-carer (brilliantly played by Brenda "Gayle Tuesday" Gilhooley) and a cursing, smoking Irish nun. The mother is straight out of Joe Orton, spiking the lodger's coconut cake with Rohypnol so she can have her wicked way with him And the opening scene is a superb set- up The two lads are watching a porn film. "They're descriptions."It helped that God's Toilet (which refers, according to a holy tramp who makes a slightly confusing appearance, to Chatham - "Yea, and all the Medway Towns") introduces unexpected elements. A typical line from Write Back Home: Dad (played by Windsor Davies, a neat reminder of the supposed Golden Age) is having a drink; son tastes it - "What's that?" he asks, "Tizer and paint-stripper?" A typical line from God's Toilet: Mum complains about her son - "He call me such names." "They're not names," the son says.