Summary: I bought one of these NC (neutral color) filters for each lens I own and for one purpose - to protect the lens. It is a whole lot cheaper and easier to replace a scratched filter than to buy a new lens. I recently bought a Nikon d7100 camera which I am learning how to use. From the limited number of pictures I've taken thus far, I do not see any added effects, the pictures are clear.
Excerpt: I have a couple of these filters in other sizes for my other lenses. I recently purchased a 50mm 1.4 and purchased this filter for protection. Glass is absolutely clear and easy to clean. This has not affected image quality at all. I shoot a lot of weddings and this is cheap effective insurance.
Pros: Clear Optics, Easy To Use, Firm Mount, Strong Construction