Re: [photo-3d] Re: Dale labs

["Dr. George A. Themelis" <drt-3d@xxxxxxx>]

> Apparently the polarization has no effect on the film Dale 
> labs uses.  I  recalled hearing about this somewhere, but it was quite 
> disconcerting to realize that many of my better slides could never be 
> projected.  

Apparently, the Dale film depolarizes the light.  This is known
to happen with certain types of film and it is only a problem
when the stereo projector has the polarizing filters BEHIND the
film.  So the light gets polarized by the filters but it is then 
depolarized by the film. 

To go around this problem you could copy your slides to a
different film, OR you could move the polarizing filters infront
of the film, OR use a projector that has the polarizing filters
in front of the film.  The Compco stereo projector has the
filters in front of the film.  Also, most (all?) twin 35mm 
projectors (for 2x2) have the polarizers in front of the
lenses (and the film).

Finally, if you use the TDC projectors (which have the polarizer
filters behind the film chips) you can pull out the polarizer
assembly and tape it in front of the lenses.

As you can see, there are many options available so it is not
a big problem... just an inconvenience since you use TDC
stereo projectors.

George Themelis