The filters I use as protection for my Nikkor AF-S 50 1.8G because the lens moves out inside pure and and I do not want that she swallows dust. The filter contains a metal thread and is thinner than the conventional filter, so the name "slim" - I was not that important, but it can not hurt, because the thread of the filter is not so out projects and looks visually good.
Making a difference to my pictures I can not tell - Pixel counters are certainly notice a difference, but it is clear that the image quality (marginal) decreases, after all, the light must go through an additional layer of glass. In practice (in my opinion) but not noticeable or decisive.
