An Ontario man has been convicted of voyeurism and making child pornography after repeatedly and secretly videotaping his 10-year-old daughter in her bedroom.

The man, who cannot be identified in order to protect the identity of his daughter, admitted he made the videos but argued he did so as a means of surveillance because he had concerns about the girl's behaviour.

He told a Thunder Bay, Ont., court the videos themselves were not of a sexual nature even though they show his daughter partially or fully nude.

The Crown, meanwhile, said the girl had an expectation of privacy in her bedroom, a space where it is reasonable to expect that someone will be naked.

Prosecutors also said two of the videos show the girl engaging in a sexual act, and the others show her naked for the purpose of titillating the viewer.

In a decision released this month, an Ontario Superior Court judge said he did not believe the man surreptitiously filmed his daughter out of concern, but rather did so to capture her nude.

"I cannot see, as a matter of common sense, how placing a secret camera in a 10-year-old's bedroom would serve to address these concerns, particularly when none of the videos showed any irregular behaviour on (the girl's) part," the judge said.

"What all the videos did show were occasions of (her) undressing."

In several cases, the girl entered the room wearing a towel after taking a shower, or was putting on or taking off pyjamas, all times where she would be expected to change, the judge said.

The judge said he deduced her father "knew this was going to happen and that is why he set up the video to make the film."

The length of the videos -- from seven to 39 minutes -- and the fact that the camera was placed in the closet then removed suggest her father was actively trying to obtain footage of her undressing, the judge said, noting surveillance videos are generally a continuous stream of recording.

Court heard the videos were discovered on a memory card after the man brought a camera to a pawn shop in 2016.

In some of the videos, the man can be seen setting up the camera in his daughter's bedroom, and there are relatively long periods in which no one is in the room before the girl arrives, court heard.

A sentencing hearing will be held at a later date.