Olympus 9mm: Fisheye vs Rectilinear

Olympus now has two lenses which include the 9mm focal range: The Olympus 9mm f/8 fisheye (my review) and the Olympus 9-18mm f/4-5.6 wide angle zoom lens. The first is a fisheye lens, and hence, it has significant barrel distortion. The second is a rectilinear wide angle zoom lens.

But beyond that, do they give you a different field of view? Below is the 9mm fisheye lens, with the Four Thirds version of the 9-18mm zoom:

Taking the same picture with both lenses yields these variants:

Olympus 9mm f/8 fisheye	Olympus 9-18mm f/4-5.6 @ 9mm f/8

So, as you can see, even if both lenses are rated at 9mm, they give a quite different field of view. The fisheye lens is much wider. On the other hand, outside of the centre, it is quite distorted.