Re: Ghosting due to high-contrast subjects vs depolarization

[P3D Kenneth Luker <kluker@xxxxxxxxxxxxxxxxxxxxxxx>]

Peter Abrahams wrote: 
 
> This issue arose because my stereo x-rays are very high contrast, white on
> black, and there was ghosting during the shows in Bellevue (worse than when
> viewed at home with a TDC.)  This was not because the film depolarized, but
> because the most effective extinction with crossed Polaroid filters is
> about 99 per cent.  Even 1 per cent of a bright, white image will appear on
> a jet black background.
> Do any readers know if any
> Brackett projectors sandwich the filters between glass or use very flat
> plastic filters?

I was standing near Bob Brackett when he (Bob) commented on the projection of 
the x-ray shots.  He was convinced that the problem was that the 
transparencies were produced using a film base that de-polarizes the light.  
He said that it is a common problem when projecting such slides.  His 
Dissolver has the polarization filters between the lamps and the slide.  He 
said that the problem could have been overcome by putting the polarizers 
beyond the lens, so the last thing the light passed through before hitting the 
screen was the polarizers.  For what it is worth.  Peter dismisses this 
explanation, as quoted above.  
Ken Luker


------------------------------