[pure-silver] Re: Filtering with infrared?
- From: "Peter Badcock" <forums@xxxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 16 Mar 2005 17:57:54 +1100
Jason,
you may want to try:
Low Emissivity Glass which is glass with a special coating
(since
glass by itself won't block much IR).
http://www.glassonline.com/infoserv/dictionary/584.html or
http://www.winrepco.com/Low-e Glass.htm
or
possibly Dichroic filters which can be made with a visible
passband.
Most domestic halogen lights (50W variety in OZ) have a
dichroic
filter on them to block harmful UV rays.
For an idea of the spectral response see the black trace of
an
IR-blocking filter at
http://www.trutek-uk.com/truetech/filters.html,
although I'm unaware of the power handling of this type.
But the area
of interest for you will be in the mid to thermal IR regions
and the
graphs don't show these measurements!
NIR(near-IR): 0.75 um to 3.0 m, MIR (or mid infrared): 3.0 m
to 8.0 m,
TIR (thermal infrared of far infrared):8.0 m to 15 m
As for water - I don't know how good it is at blocking
thermal IR, obviously if you had a spare second fish tank to
place in front of the light this will help but will add a
green cast to the light because of the impurities in the
glass.
regards
Peter Badcock
> A question was raised at an aquatic photography forum that
> I was hoping someone here could help with regarding
> infra-red filters and heat. For photographing small fish,
> a small 'photo' tank is being used with a Halogen 300W
> light. Needless to say, the tank is only being used for
> about 5 minutes before the water starts heating up too
> much. The metal mesh helps, but not enough.
> Someone suggested improvising a heat filter to absorb some
> of the infra-red light (but letting the visible light
> through). He said that glass can do this (hence the
> greenhouse effect in a proper greenhouse) and said that
> some types of plastic probably would do too - he
> remembered his first phtographic enlarger had plastic
> filters, including one labelled 'infra-red'. Any
> suggestions on what could be used?
>
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