Plastics are optically altered by stress. You can get some very pretty patterns by putting a piece a plastic film or strip between two crossed polars. It may be used to analyse stresses in a plastic model of a load bearing beam to aid beam design. I think the correct term is "birefringent". Or just make pretty patterns. I don't know how to make them go away. Chris Web Page http://www.chrisspages.co.uk/ |> -----Original Message----- |> From: owner-photoforum@listserver.isc.rit.edu |> [mailto:owner-photoforum@listserver.isc.rit.edu]On Behalf Of Gregory |> Fraser |> Sent: 15 September 2003 16:22 |> To: List for Photo/Imaging Educators - Professionals - Students |> Subject: Interference patterns in plastic |> |> |> I have an image of a child's translucent plastic car backlit by |> sunlight. I took the image a while ago and probably used a |> polarizing filter. Using curves or levels in Photoshop, there is |> a very limited range where interference patterns are not visible |> in the plastic. I know clear Plexiglas will show interference |> when viewed through a polarizing filter but I didn't think all |> plastics would exhibit this. |> |> Could it just be my scan or will all plastics be goofified by |> polarizing filters? |> |> Greg Fraser |> Senior Technical Support Officer |> GTIS - PWGSC |> 457 Richmond St., 6th Floor |> London, ON N6A 3E3 |> voice (519) 675-3409 |> fax (519) 645-4304 |> |> |>
