Ann,
I was just trying to do this and spoke to the people at Century/Schneider Optics in LA. I had used a Nikon lens in this manner before. However, they let me know that they don’t make an adapter for the new Canon EOS lenses which I have for my still camera. I haven’t had any luck looking anywhere else.
You may still be able to find an adapter for older film lenses somewhere.
Dave Adams
Shooter/AC/AP/Phantom Tech
Washington, DC