TLDR; Man on a boat holds a one-hand 8mm cine tape camera to his head, and transfers mental images to the tape using psychic powers.
I think I watched this in the 80s – probably a 60s film. I can only really remember one scene, but it’s a pretty standout scene.
Style of the outfits and boat were very Cambridge / Oxford boating, but the scene may have been on a London lake.
I think the man was gay and persecuted for being so which lead him to take actions to punish his tormentors.
The cine camera looked something like this: