TORONTO - Ontario's top court has overturned the acquittal of a man who claimed he collected more than 600 images of child pornography for artistic purposes.

Robert Katigbak admitted at his trial that the 628 images and 30 video clips of "real children and real abuse" on his computer constituted child pornography.

"Suffice it to say they are repulsive in the extreme to anyone who cares about children and the protection of children," Justice Robert A. Blair writes for the three-judge panel of the Court of Appeal for Ontario.

There were also more than 46,000 images of adult pornography on his computer.

Katigbak was acquitted in 2008 of one count of possession of child pornography. In a judgment released Tuesday, the Appeal Court set that aside and convicted him instead, referring sentencing to the trial judge.

Katigbak, a photographer, testified at his trial that he collected child porn over a seven-year period for research. He wanted to create an exhibition that would present the issue of child exploitation and pornography from the perspective of the exploited child, Katigbak said.

He never actually presented such an exhibition. He said he didn't have money to rent space for it.

The Criminal Code has an exemption that encompasses artistic merit, but the language was strengthened in November 2005 to include the phrase "legitimate purpose."

Katigbak relied on the "artistic merit" and "educational purpose" defences as they existed before then, but the Appeal Court ruled he could not because the materials Katigbak possessed had neither artistic merit nor an educational purpose.

"I question whether any reasonable observer could conclude the respondent either had the purpose or intention he professed to have or that he had possession of the images for a 'legitimate' purpose related to art or education," Blair writes.

"Perhaps there was some minimal connection in his mind -- to create some ill-defined art exhibition at some unknown point in time -- but on any objective view of the evidence he did not have possession of these images in this fashion for that purpose."