Re: [Phys-l] Hewitt's three answers - Flicker Afterthoughts.

[brian whatcott <betwys1@sbcglobal.net>]

Thoughts on perceived flicker from incandescents, fluorescents etc.

Flicker is a phenomenon of perceived brightness variation.
It means that methods used to quantify flicker should attempt to 
replicate the physiological substrate.
One measure is to fit a human photopic response filter to the photo 
sensors used to identify the
relevant variation. Contributors mentioned a high speed video camera 
(near IR sensitive), a photo tube
  (Hamamatsu data show response curves from 150 nm to 1000 nm) and a 
solar cell
  (These too can respond well into the infra-red) see
http://jp.sanyo.com/solar/amorton/en/feature/index.html

Luminous efficiency was also associated with filament mass and gas-fill.
  As well to mention the the advent of coiled-coil filaments signaled an 
improvement
in that area

Sincerely

Brian W


On 3/30/2012 11:05 AM, Bernard Cleyet wrote:
> On 2012, Mar 29, , at 21:49, Ludwik Kowalski wrote:
>
> > P.S.
> >
> > Looking at the Figure 1 again I think that the amplitudes of fluctuations would be much smaller that 22%, if one was measuring temperatures, rather than light intensities. Yes I am thinking about the T^4 law. The tungsten spiral filament probably behaves nearly as if it were an ideal black body.
> >
> > The challenge is how to measure the temperature without depending on radiation. What about plotting the R(t), where R is the resistance = v/i? The dependence of R on temperature is nearly linear, in a narrow range of T.
> >
> > Ludwik
> > Looking at the Figure 1 again I think that the amplitudes of fluctuations would be much smaller that 22%,
>
> According to Levi (Applied Optics)  probably so.  Here's the graph:
>
>
> http://www.cleyet.org/Misc._Physics/Lamp%20flicker(D).tiff
>
> bc  thinks breaking the envelope and using micrometer calipers is the next step.
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