Floor-essent lamps for viewers

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Tue, 7 Oct 1997 14:33:01 -0500
>From: P3D  Bob Howard  <bobh@xxxxxxxxxxxxxxxxxx>
>Subject: Re: Flourescent lamp for viewer? (PHOTO-3D digest 2339)

>RE: Don comments on my suggestion about a small camping latern 
>flourescent lamp as an illuminator for a viewer to get more 'light 
>table' effect of 5500K!
>He worries about UV. Well, the glass does not transmit the UV 
>(Flourescent black light UV lamps do have quartz bulb to pass UV)
>in the ordinary flourescent lamps. The pass the visible light the 
>phosphor produced when excited by the UV retained inside the tube so 
>to speak. For that matter camera lenses and window glass do not pass 
>UV either so UV filters are for the near UV or excess blue light at 
>high altitudes. BobH
>If UV were a problem light tables would be a hazard as the plastic 
>diffuser over the flourescents would pass the UV I believe?

Unfortunately, "the glass does not transmit the UV" may be an 
oversimplification in this case. The fact that regular glass would not
be a good choice for a UV optical system doesn't necessarily mean that
it blocks *all* the UV. You might be delighted if your pond liner retains
95% of the water in your pond, but displeased if your roof lets 5% of the
rainwater through. With the extreme proximity and brightness of the light
source, and concerns regarding the role of UV in the development of
cataracts, it's worthwhile to pay some attention to the details.

Some of the UV is absorbed by the phosphors (thus causing them to emit
visible light), some is absorbed by the glass, and very likely some gets
through. Also, there are different wavelengths of UV, with different health
effects. If we are to be assured that this kind of fluorescent light is safe
for this particular application, it would be nice to have some actual
numbers (and perhaps an improved spelling of the word "fluorescent" would
improve our confidence in you as an expert witness on this topic :-).

John R (who rates that misspelling of "fluorescent" somewhere in the
range of fingernails on a blackboard, on a scale of irritants)


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