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Re: [TCML] flourescent light trick
For all of you rotating mirror guys - what do you use to look at the spark?
Do you use CCD cameras or do you have access to some high speed film? I
have seen some of the older film-based high speed rotating mirror cameras,
and there was some apparent effort put in to replacing the film frames with
inexpensive CCD chips. I have no idea how they avoided the mirror motion
blur on the older cameras.
With a large enough radius from the mirror to the CCD chip (and a bright
enough light source) you could probably get pretty short time windows on the
sparks, and with CCD chips/cameras you could afford to take many pictures to
get the shots you want of the breaks in the arc, which would be very cool.
On Nov 17, 2007 11:06 PM, William Beaty <billb@xxxxxxxxxx> wrote:
> On Wed, 14 Nov 2007, Chris Swinson wrote:
>
> > One thing I noticed with flu-tubes, that if you walk away from the coil
> > slowly, it goes dim, but just before it goes out totally the light
> > alternates inside the tube, such as 1" on, 1" off.. all the way up the
> > tube..
>
> That's called "positive column striations," and fluorescent tubes always
> have them all the time... but usually they're vibrating back and forth too
> fast to notice. If you have a straight piece of clear neon sign tube,
> and sweep it rapidly back and forth while lit, then you can see the moving
> patterns. They're also called "jellybeans" by neon sign makers. With
> just the right gas mixture and high-freq power supply you can create
> stable ones in a neon sign, so the sign is made of "dotted lines."
>
> I wonder if sparks at one ATM also have them. If the blotches are moving
> around fast, we might never realize that they exist. (View sparks with a
> spinning mirror and look for swerving stripy patterns.)
>
>
>
> > always thought that was pretty neat! never understood why it would
> > light up alternate inches in the tube though!
> >
> > Chris
>
>
>
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