I calibrate my lenses a few times a year using the focus pyramid, a cheap yet very useful $25 tool. If you're unsure of how to calibrate your lenses, I recently wrote an article on SLR Lounge detailing the process for both Nikon and Canon DSLR's. Don't assume your new lenses are going to focus accurately, most of the time they won't, you need to calibrate them. Click on the image above to purchase the pyramid, here is the link to the SLR Lounge article - http://www.slrlounge.com/calibrate-lenses-simple-fix-blurry-images/