Bob Solomon wrote about this lens:
The Imagon needs at least a 5:1 lighting ratio to do it's job. The aperture should only be controlled with the disks as the correction of the edge of the Imagon is cut-off if you use the aperture control in the lens or shutter. The softest results are with no disk. Then the next softest is with 5.8 to 7.7 disk with all of the edge holes open, next softest would be with that disk with all holes closed. With no disk the aperture is at 5.8. With the 5.8 to 7.7 disk the exposure is 5.8 with all holes open and 7.7 with all edge holes closed. The next softest result is with the 7.7 to 9 disk with all holes open, next would be with all holes closed. The lens is very sharp with the 9 disk with all hole closed.
The disks can be set with edge holes partially closed, if desired. The Imagon needs a strong main light in order to create the halation that is the mark of the Imagon. You should not be using flat lighting as the key light like an umbrella or soft box.
As the focus changes with the settings of the disks it is very important that you focus with the disk in place and set as you want. If you change the disk or the hole openings the focus will shift. When a strong point light source is in focus with an Imagon a cross is formed on the gg. So a small, bright flashlight at the subject position at the point of sharpness will aid you in focusing the Imagon and to learn what a sharp Imagon image looks like on the gg, compared to an out of focus image. If you want to reduce exposure use the ND filter so you maintain the desired softness effect.