The film-making style of the late Charles Carson veers, undeniably, towards the creepy. A Somerset farmer with a hobby that seemed to have taken over his life, Carson had a penchant for filming cows giving birth (with closeups of the placenta). Then there’s his footage of burying his pet cat, Pandy, in the orchard. “You’d never think he was dead, would you?” Carson marvels, shoving little Pandy in front of the camera. Erm, the rigor mortis is a bit of a giveaway. Weirdest of all are the photos Carson took of his elderly mother after she died – pushing her around the farm for three days in a wheelchair so the cows could pay their last respects. A neighbour recalls bumping into the pair: “Your mum doesn’t look too well.” “No. She’s dead.”

“Dark but friendly dark,” is the verdict of one of the talking heads padding out this documentary about Carson’s magnum opus A Life on the Farm, an unclassifiable home movie. Carson often appears in front of the camera, with the jaunty but slightly off manner of a daytime TV host gone rogue after a few gins. In the art world, he would be labelled an outsider artist; he was self-taught and there’s a naive quality to his film-making. Some moments of Monty Python comedy silliness are evident: shots of cardboard cutout skeletons riding cows or Carson himself toppling off his sit-on lawnmower.

The documentary’s director, Oscar Harding, explains that his grandfather was a neighbour of Carson’s in the wonderfully named village of Huish Champflower, and he was first shown A Life on the Farm age six. Stretching this curiosity of a man and his work into a full-length documentary is perhaps pushing it. But there is no doubting Carson’s dedication to his craft: at his brother’s funeral he asked the pallbearers to stop lowering the coffin down so he could get his camera in a better position.

• A Life on the Farm is released on 8 September in UK cinemas.