Mitch Cairns' loving portrait of his wife, Agatha Gothe-Snape was a "standout winner" among the Archibald Prize's board of trustees, according to artist-judge Ben Quilty.

Quilty has described as untimely and "ungracious" John Olsen's criticism of the painter the same day as the Art Gallery of NSW Board of trustees, David Gonski, announced Cairns had taken out the famous portrait prize, worth $100,000.

Mitch Cairns, the winner of the 2017 Archibald Prize, his winning painting and its subject, his partner Agatha Gothe-Snape. Credit:Kate Geraghty

John Olsen, the subject of a Nicholas Harding portrait, a prize finalist, derided Cairns' selection as "the worst decision" he had seen and nothing like the style of the modernist master Henri Matisse to which it had been compared.

"We get criticised constantly that [the Archibald] is a traditional, old, boring show and then when a young really ultra contemporary painter wins it the old guard comes out and smashes him," Quilty said.