EF-S Lenses for the bold.

[magnesiumnitrate]

I needed a wide lens for some real estate work I have coming up. I've invested heavily in the telephoto end but I'm not quite ready to plop down a ton of cash on the 8-15L, or even the 16-35L. Instead, I bought the 10-18 EFS for $350 (with the new 50 1.8 stm to boot). Turns out, ML 3k cropped on the 5d 3 fits just inside the image circle even at 10mm. The lens is also usable for stills from 14-18 on the FF 5D.

You'll have to hack (literally, hacksaw) off the plastic bit that prevents you from mounting it, but it's so worth it. It appears that most EF-S lenses can be converted easily. The 17-55 2.8 literally requires no tools, the plastic just pops off.