[pure-silver] Re: Polarized Screens (was duplicate info)


----- Original Message ----- From: "Adrienne Moumin" <photowonder2010@xxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, June 26, 2005 12:19 PM
Subject: [pure-silver] Re: Polarized Screens (was duplicate info)


Eric, can you please provide more info as to exactly what these "polarized screens" are? Also, how do you keep them from melting? I have can-type reflectors which are pretty big but the HOT bulbs (500W) stick out beyond them. Do I just need to get even bigger reflectors?

Sorry, all, for taking this so far afield of the "pure silver" list topic, but sometimes one must jump on an opportunity when it arises. Off-list, I would've learned something; posted, everyone else does, too.

-Adrienne Moumin

Polarizing material is available in plastic sheets. There is a coating on them made by dispersing a crystaline material. I've forgotton the details but the process was invented by Dr. Edwin Land of instant camera fame. The plastic is used on lights in the in the same way as color filters are. They can be mounted on large carboard frames on separate stands and spaced away from the lights. As long as the light striking the subject is polarized its fine. The idea is that at about a 30 degree angle the specular reflection from non metallic objects is polarized. If polarized light is used to illuminate them the surface reflections can be eliminated. When a polarizing filter is also used on the camera the light from unwanted reflections can be virtually eliminated. You may not need this much elaboration.
BTW, if you have adequate strobe units to illuminate the original they have the advantage of pretty much eliminating blur from camera shake etc, and subject the original to less intense light and heat. Not a big deal here.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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