Fisheye lenses compared

I like fisheye lenses: They can cram an impressively wide field of view into the image frame, and create perspectives that you would not be able to see with the human eye. Another aspect of fisheye lenses is that they create a lot of barrel distortion (rounded images), which you can remove through a defish process, or retain in the final image.

Here is a collection of fisheye lenses for Micro Four Thirds and other systems:

From the left: Samyang 7.5mm f/3.5 (my review), Lumix G 8mm f/3.5 (my review), Yasuhara Madoka 180 7.3mm f/4 (my review), Olympus 9mm f/8 (white) (my review), Lensbaby 5.8mm f/3.5 (the biggest) (my review)

There are basically two types of fisheye lenses: A circular fisheye lens renders a circle in the centre of the image frame, which usually extends to 180° all around. A full frame/diagonal fisheye, on the other hand, renders the full imaging sensors, and usually extends to 180° from corner to corner.

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.