I've come across another option for those wanting the "wrinkled," irregularly-shaped film surface without sacrificing visibility in or out...
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I grabbed a spare piece of material from the guy and shoved it in front of the welder's shield in my bucket:
While it is not green, it does give a nice irregular-surface appearance (and a verrrry slight mirror-feel). And there is absolutely no visual difference looking through it...none.
So, by placing it in front of the shield, you get the camera flash-blocking performance of the welder's shield, plus the surface texture of a film.
Now, these coatings are expensive. BUT...if you can contact a company like this near you and ask for a sample, you will likely get an 8.5"x11" sheet =)
Tell them you have a very expensive painting next to a window and you are concerned about the paint fading from the sun. They'll send you out samples in a hurry =)