Addy101
Well-known
First off, I don't use Lightroom (tried it, hated it) - but even if I did, there is no such thing as a free lunch.Distortion can be handled by using Adobe Lens Profiler available at no cost from Adobe.com. I have the Rokinon ( Samyang ) 8mm manual lens for my Fuji X-Pro1. The lens profiler has most of these lenses, but you haveto check the menus of the other APSC cameras before you find the lens profile you want.
For instance, the 8mm Samyang is listed under the Sony menu. The profile downloads automatically into your Lightroom. It works very well.
That 12mm seems to be a better choice. Enjoy Frank.