Here is the story:
“The clip below was an experimental attempt to automatically watermark clips and stills after one of my fashion clips was edited and broadcasted by one of the commercial regional TV channels in France without my consent and without any credit.
In fact the credit was cut off the original clip. However, for the time being, I prefer not to disclose any information about the TV and the people involved in the process.
Al suggests using dry transfer letters and UV filters for making a small marking on the lens. Since this mark is pretty close to the front element it won’t actually be seen where the image is sharp. Instead it would only be seen at out of focus specular highlights (similar to the Bokeh Masters Kit).
Here is how the dry letters are transferred.
Alternatively, Al suggests using a simpler and cheaper watermarking solution with a permanent marker and a transparent nylon film
The sample movie that Al provides has the effect pretty strong, but I wonder if a more subtle effect can be used to effectively watermark videos.