[photo-3d] Silver screens

["John Goodman" <jgood@xxxxxxxx>]

John A. Rupkalvis wrote:

> Screen manufacturers that make silver screens for stereo
> projection actually use a coating that has very fine aluminum
> flakes in suspension.  (Some paints are now available that
> have a similar composition, and do work, but it is best to
> test them). 

The materials and techniques that the Stewart, Hurley, and 
other companies use must be special and involve considerable 
finesse (such as spraying coatings upwards to a suspended 
sheet of material?), else their products would not be so fine nor 
so expensive.

On the other hand, I've been surprized by how well certain 
cheap aluminum flake paint works for stereo projection. But 
there are a few obstacles. When sprayed on a hard, smooth 
surface, I found the result too "specular", i.e. the projection axis 
is nicely bright but axial falloff is too rapid. When applied to a 
fabric, the results were much better, with more uniform 
illumination off axis. But unless the fabric is held very flat, even 
small wrinkles or surface variations appear intrusive during 
projection.

A local Kyoto company sells a variety of metal powders, 
including aluminum, so experimentation beckons. The metallic 
flake used in most aluminum paints seems to be very fine 
(about 30 microns?). I'm wondering if adding coarser particle 
sizes would be advantageous for stereo projection, or if the 
benefits of possibly increased reflectivity would be outweighed 
by a tendency toward hot spots, regardless of the texture of the 
substrate. Are there formulae and recipes for this kind of thing? 
Most likely it's an art, with results depending on a host of 
variables, like so many enjoyable things.

John Goodman

 

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/