The decision overruled two previous verdicts which had given the man a four-month jail sentence.
The woman had agreed to the use of a video camera to project live images of them having sex on to the bedroom wall but did not know the camera was hooked up to record as well.
The court took into account that the man had not distributed the video material but gave it to the woman in a package with a note saying, "These are my last thought for you" after the relationship had ended.