Beyond the Imagon
I don't believe that the Imagon's disk is the final word on using apertures to manipulate spherical aberration
My latest soft focus lens uses a homemade apodization filter made from a 120 film negative. To make the filter, I shot an image with a dark center and gradually lighter exterior. The negative makes a pretty good apodization filter.
Shooting through a negative causes a slight loss of contrast, but that can be corrected with a little processing.