A former Brisbane priest's claim that indecent photos he took of a boy were "artistic", not sexual, has been challenged by a judge.

Michael Ambrose Endicott, 75, is being sentenced on Monday after being found guilty last week of three counts of indecently dealing with a boy for taking nude photos of him about 30 years ago.

"This man was walking around the child, who was completely naked, taking photographs of him from the front and back. I don''t understand how that sounds artistic," Brisbane District Court Judge Leanne Clare, SC, said.

AAP