In article , Richard Schtzl <Richard.Schaetzl@xxxxxxxxxxxxxxxxxxxx>
writes
>Gareth Knight wrote:
>>
>> People,
>>
>> Does anyone know of a good technique for photography through stage
>> smoke ?
>
>Have you tried infrared film? I guess the long wavelength of infrared
>light will pass the smoke better.
>
>Richard
>
>Someone who has exposed not one infrared film. :-(
>Expert advice is welcome! :-)
>
In principle you are correct, but I doubt if moving to the near infra-
red (some call it infra-pink!) of IR film will make much difference in
this context.
I have designed thermal imaging cameras for the past 20years - including
the most popular fire-fighting cameras in the world. These generally
work in the atmospheric windows of 3-5micron and 8-12micron, although
the only successful firefighting devices operate in the longer waveband
specifically because it is the band that cuts through the smoke, whilst
the 3-5micron band is marginally better than visible.
Obviously a lot depends on the type of smoke and the particulate size,
but we frequently use stage smoke for technology demonstrations to
highlight the difference between the two thermal bands. I have also
observed many NATO exercises where battlefield smokes have rendered
3-5micron cameras useless whilst significantly inferior 8-12micron
cameras have operated without hindrance. I can't imagine wavelengths of
less than 1micron penetrating stage smoke significantly better than
0.4-0.7micron visible light over the short path lengths involved,
although it does scatter less at lower densities over longer paths -
thats what gives such vivid red sunsets and the blue sunny sky.
[ Mr Anderson will note that I have used micron throughout this text,
rather than alt-230, despite the habit of using this extended character
several times a day for many years. ] :-)
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
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