I had However, after using it for the last few months, I am still not 100% happy with the lens. I still have issues with soft focus. Using all the basic rules such as using single focus, focusing on the eyes, using a narrow DOF like 5.6 (as opposed to a very shallow DOF like 2.8) still does not seem to bring out those crisp, sharp images. I am starting to think that there may be some issues with the lens itself. Is there a way to ensure that the lens is absolutely not faulty? I bought it over the INTERNET but do have warranty on it for 12 months.

How do I ensure that the lens is not faulty?