Perfect fisheye lens

For a long time now I've been searching for a viable way of doing fisheye renders with Kerkythea. I tried using modeled lenses with the dielectric glass material, and also using a reverse method with a spherical mirror ball. The problem with those is that they often get black or white lines crisscrossing your render, looking like the wireframe (most noticeable when rendering without AA)

However, after some recent fiddling around in Kerkythea, I found a very handy and simple way of doing fisheye!
Simply place a vertical plane in front of your camera (the front face needs to point towards the camera), either by placing it in SketchUp, or by adding a vertical pane in Kerkythea, and then copying over the coordinates of the camera (in the Advanced Settings window)

Then you need to set the vertical plane's material to be [Dielectric / Glass], and add white to the refraction (no reflection though (Uncheck the Fresnel if you don't want the edge falloff)).
Now, if you set the IOR to be below 1.0, you get the fisheye effect, but it also increases the brightness, so feel free to adjust the weight of the refraction, or you can always adjust the exposure after render
You will need to experiment with the focal length and IOR a bit, until you get it to show the entire 180-degree circular image. (if you set the IOR too low, it will become very small on the render)


Now just add some diffraction, and you'll get some pretty neat chromatic abberation (works best with BiPT, MLT & BMLT)


Kerkythea is amazing!

Interesting.
What is the goal of having the fisheye lens effect? Is is simply artistic desire, or you need a spherical camera?
You can of course choose a Spherical camera already in KT without any effort.