I know this thread is long dead, but I got a solarized sun similar to the one in Adam's image by pointing the camera directly at the sun and giving a (relatively) short exposure of around 1/30th using Pan-F developed in Rodinal. I dont believe the film or (certainly) not the developer have anything to do with it. its a function of the intensity of the light. I dont have a scanner, so you'll have to trust me.^^