More specific details here. I also found a video on Youtube that went onto the optical details in more depth but as it was focused on the medical application and contain subjects people might find distressing did not post a link - search for "Katharine Hanlon Cross-polarized and parallel-polarized light" if you're interested - also contained an interesting slide on the impact of colour with skin depth which is OT here but curious how it would work with fresnel when creating SSS.