Those are good tips above. I have almost the same set-up (7D and I have used my 18-135 at times, but now use my Sigma 30 and Tamron 90 over that lens). You should get some sharp shots. Make sure your pumps are off... what settings? did you use Tripod, yes or no? If you are shooting hand held and your shutter speed isn't up high enough, you aren't going to get that really sharp shot. Try getting your camera stationary (even if you can put it on a chair or some other object), and use the 2-sec timer. Make sure the focus is bang on before taking the shot, which includes not being too close (which shouldn't be an issue with this lens). That should produce a sharp image.