Re: colored vignetting

[P3D Peter Davis <pdavis@xxxxxxxxxxxxxxxxxx>]

> Allen wrote:
> 
> >I am at a loss to understand here...
> >If you want to eliminate the colored vignetting, remove the filtres.
> >
> >The colored vignetting IS the 3-D information in the particular
> >system you are trying to make.
> 
> The principle that makes anaglyphic SL3D work is to overlay a blueless
> image from the left perspective with a redless image from the right
> perspective on the film, then reconstruct them with red-blue glasses.
> This is not vignetting (it is also not accurate to state that "the depth
> information is encoded in the red-blue fringes of out-of-focus areas"
> as someone else has done).
> 
> Vignetting occurs because the apertures for the two images are not
> centered on the lens axis, causing the picture to be overly red on
> the left and blue on the right.

I took a closer look at my Q-dos last night.  What it actually looks
like is that the red and cyan filters are intended to cover the entire
lens aperture with no clear band between.  However, to make it
possible to switch the filters in and out, they fold in from different
sides of the lens barrel, and thus meet with a seam in the center.
Also, each side of the filter actually collapses when retracted, so
there's a curved seam through each of the color areas.

The instructions for the lens state that the effect works best with a
wide aperture setting.  (There's a revision note that specifically
says to use f/5.6).  I don't know if this is because of the
requirement to have some out-of-focus information to convey depth, or
becase at small settings, the center seam is a proportionally larger
part of the overall area.

-pd

--------
Peter Davis		       "Education is not the		 617/873-4145
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