70 degree lenses for AI sol

[Madreefer]

They come with 4 70 degree lenses and 4 40 degree lenses.
You can change the configuration and it supposedly helps with the spread. The difference betwen the lenses is a little dot in the center of the lens. There was an article on the net explaining all of this and I cant seem to find it anymore. Maybe if someone else can remember or find it they can chime in.