This might kind of seem harsh, but I think it takes into account that there's a lot of knowledge to have in most subjects, and most people take very high levels of knowlege for granted. When I recruit, and when I train people on hiring, I propose a very curious rating on a zero to ten scale:
- don't know how to spell it
- heard of it
- wandering around the bookstore to find a book on it
- did some tutorials, half a clue
- used it a bit
- familiar with most stuff about it
- did a very substantial project with it