From: robert (robert@RobertSchaller.net)
Date: 12/11/01-03:46:09 PM Z
Sandy (et al.),
I'm very curious about your mention that the inverse square law does not
apply to a bank of fluorescent tubes. Might you explain a bit more, or even
give the math (or a reference to it)?
Also, I am exposing gum dichromate emulsion to a bank (so far, just two)
of F40BL bulbs (is there another that might be better?), and wonder whether
the type of balast I use makes any difference. As it is, the bulbs come on,
but I'm having some problems with the gum not hardening. It is probably not
the exposure, since I get a very readable (if faint) dichromate image, but
at this point I wonder about everything.
Any info from anyone would be appreciated,
Robert Schaller
on 12/11/01 10:30 AM, Sandy King at sanking@clemson.edu wrote:
> Jeff Foster wrote:
>
>
>> so last night I went down to my shop and hooked up a ground wire to
>> all three ballast (via the screw holding them to the wood top) and
>> then to the ground on the ac cord. bingo - no delayed start and no
>> flicker! very cool solutions. I looked closely at the wiring
>> schematic on the ballast label and it does show a little ground
>> symbol leading from the case...hmmm.
>
>
> Congratulations. Wiring schematics can be useful when all else fails!!
>
>>
>> thanks to all who supplied insight - now on to printing ( banding
>> test - even with the inverse square law for light fall off....)
>
>
> Interestingly, the inverse square law only applies to point source
> lights, not to a bank of fluorescent tubes being used very close to
> the exposing plane, essentially functioning as a diffuse light
> system. In other words, contrary to expectations, doubling the
> distance of the tubes from 2" to 4" from the exposing plane will
> *not* result in a 2X increase in exposure time. It will in fact be
> far less, perhaps barely enough to even notice.
>
> Sandy King
>
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