Justine Varga's prize-winning portrait has provoked controversy. Credit:Wolter Peeters "She was quite bemused that I asked her to inscribe on the negative and basically spit on it," she said. "You know, she's my grandmother. She's not really into that sort of thing." Ms Varga's work was awarded the $20,000 prize at the Tweed Regional Gallery on Saturday by judge Shaune Lakin, who called it a "very complex photographic portrait". "It made me think a lot about the act of the making a portrait – about what it means today to make a photograph of someone else, even if in the end it doesn't reveal what they look like," he said. Dr Lakin, a curator of photography at the National Gallery of Australia, also pointed out that photographic images, such as photograms, had long been produced without cameras.

Justine Varga's Maternal Line features scrawls made by her grandmother onto a piece of film. Credit:Stephen Oxenbury But Ms Varga's portrait has provoked a debate among photographers about whether it should have won the prize. Dean Sewell, a former Sydney Morning Herald photographer and founding member of the Oculi Photographic Collective, said "it was probably drawing a long bow" to call the work a portrait. "To me, it seems a portrait essentially reveals some characteristic of the person it portrays," he said. Mr Sewell said he thought the image revealed more about the artist's practice and her methodology than her grandmother.

Mr Sewell, who judged the Olive Cotton Award in 2009, said he would "probably not" have awarded the $20,000 prize to Ms Varga's work: "I probably would have gone for a more recognisable portrait." Seventy of the 72 portraits in the exhibition catalogue feature a human form, but Mr Sewell said: "It's obviously very subjective what a portrait is and that's what is being debated a lot on social media." The entry fee for the prize is $33, but entrants can spend thousands of dollars on printing, framing and transporting their works. "People are already questioning whether they will bother entering again because of the sheer expense of entry," he said. Mr Sewell said it was not a photograph "in my opinion". "Generally photographs are things that are produced in cameras. They're the only photographs I produce."

"That it's placed onto a piece of emulsion, whether that constitutes a photograph, who really is to say?" he added. The award's entry requirements are broad, with portraits required to be "Photographic, archivally sound, still and two-dimensional". Ms Varga said: "I could have taken a photograph of her in that act of testing pens because I do take photographs with the lens as well. "But for me there's something about getting rid of the camera as an intermediary between the subject and the photographic paper," she said. "There's an immediacy there with her gesture recorded onto that film surface." Polixeni Papapetrou, whose work My Ghost, a silkscreen portrait of her daughter Olympia, was highly commended, is also an unconventional photographic image.

"A camera was involved but the end product is not a photograph but it's a silkscreen made from a photograph," she said. "So this is where it starts to get interesting." Whether Ms Varga's winning work was a portrait was a "tough question", Ms Papapetrou said. "It's so subjective and I'm confused. I have no answer for you because I'm still trying to work through the process myself." Ms Papapetrou said the choice of Ms Varga's work had divided opinion. "I think some of the other entrants will be quite shocked and disappointed in the sense that it is a portrait prize and it doesn't constitute a portrait," she said. "And they feel a bit cheated maybe."

The Olive Cotton Award 2017 is at Tweed Regional Gallery in Murwillumbah until October 8.