Lightroom 4 Lens Profiles
Adobe profide a lens profile downloading tool where you can search for a specific lens.
They also provide a lens profile creating tool which comes with detailed instructions. To create a lens profile you will have print out some suitably sized charts and take photos of them at different angles, apertures, zoom levels (if using a zoom lens) and load all the images into the creator for it do create a profile.
|Nowhere by Nanard 92|
from The Illusion of Depth and Distance
|Green Tomato by lim yau tong|
from Growing Fruit