[alt-photo] Re: UV Source

[Richard Knoppow]

----- Original Message ----- 
From: "Trevor Cunningham" <trevor at chalkjockeys.com>
To: "The alternative photographic processes mailing list"
<alt-photo-process-list at lists.altphotolist.org>
Sent: Thursday, January 27, 2011 10:20 PM
Subject: [alt-photo] UV Source


>A lot of the images I shoot or IR images. But I've recently
>been looking into recording UV and came across these
>products. I was wondering if anyone has experience, or
>knows how in/effective a hand-held UV source might be:
>
> http://www.mr-chemie.de/mediaDownload.php?mId=2147
> http://www.mr-chemie.de/mediaDownload.php?mId=1566
> _______________________________________________

     Near UV sources are easy to find and will cause many
materials to fluoresce. They are widely used for many of the 
printing processes discussed in this list.
    Photographing the fluorescense is not difficult. 
However, recording of images directly by UV is not trivial. 
Some films are sensitive to near UV but most
lenses, especially modern ones, cut off sharply beyond
visible blue light. Some older lenses have cement which
flouresces under UV. That may not be a problem in itself but
the fluorescense indicates absorption of the light. There
were special lenses made for UV using fused quartz and other
materials that transmit it well. UV is commonly used in
optical microscopes to increase resolution. In about the
mid-1930's UV was used experimentally for photographic sound
recording in order to increase resolution by concentating
the image at the surface of the film to eliminate scattering
(irradiation). The problem was finding a source intense
enough for the very slow film that was used for recording.
The technique was obviated by improved films.

--
Richard Knoppow
Los Angeles, CA, USA
dickburk at ix.netcom.com