IRIX, a company in Switzerland, have made an amazing 11mm lens that not only has some of the best distortion control for a lens of this length, but it covers full frame. Yes, an 11mm that can cover an A7R, A7S, 5D, etc, etc. It's mind blowing. The maximum aperture is an F/4

This lens is EF mount and has an electronically controlled aperture. A 'smart' EF mount with electronic contacts is needed to control the iris. Camera mount adapters without will result in the lens being stuck at F/4 and unable to be stopped down.

I've used this camera on the Canon 5D, Canon C300mII, Red Epic and Red Dragon. The distortion control and image circle combination is absolutely amazing.

This is NOT a fisheye lens. While there is perspective distortion from the extreme FoV, straight edges will have hardly any bend when on the edge of the image. This is a great lens if you need extreme wide angle.

This lens is best used with cameras that have internal ND's, such as many popular Canon, Arri, Sony and Panasonic cinema cameras. The lens can accept rear ND gel inserts, but it's much easier to simply use internal ND's if possible and the gel inserts might not always be available due to supply.