Re: Possible septum material

[Joel Alpers <joel.alpers@xxxxxxxxxxx>]

Greg Erker wrote:
> 
> >From the cameramakers list:
> 
> >I received some fabric swatches from  Beacon Fabric and Notions
> >(1-800-713-8157).  A fabric that is called Wet-look Stretch Vinyl looks
> >like it might make a good bellows fabric.  Here's their description:
> >"Wet-look, stetchy vinyl-coated polyester. Suitable for raincoats or
> >aother waterproof garments."  I got a black sample.  It also comes in
> >white and yellow.  It is shiny (wet-looking) on one side and matte-ish
> >black on the other. It is very light weight and flexible.  In holding it
> >over my eye and looking at the sun, I couldn't see any light.  If I
> >streched it a ways, however, I could.  When I doubled it over, I
> >couldn't see any light even if I stretched it.  It costs (from this
> >supplier) $14.45 a linear yard (it is 54" wide).  I was thinking of
> >using this fabric both for the inside and outside layer of a bellows.
> >How could I tell if it is really opaque? I thought that I might wrap two
> >layers around a film holder with the darkslide removed, and then let it
> >in the sun for an hour or so.  If the film shows no increased density
> >compared to the control  (a piece of film loaded in the other side of
> >the holder with the darkslide kept in place), wouldn't it be fair to
> >conclude that this would work as bellows material?  Any suggestions
> >appreciated.
> 
>   Might work to separate the L&R lenses and
> stretch when you focus in and out.
> 
> Greg

Sounds interesting. One caveat is that things are not always as opaque
as they seem  ;)

A friend made a replacement dark slide for me (4x5 camera) out of
a white plastic sheet (styrene? The stuff you can get at hobby stores
in various thicknesses). He painted both sides flat black. We found
that a sheet of film put in that holder fogged badly, even though
you couldn't see a hint of light through it.

So testing is in order...

Joel.