How to filter out blue light?

crossposting to sci.chem, and sci.astro. Originally posted only to
alt.sci.physics

On Mar 24, 6:31*am, Fred wrote:
How to filter out blue light?
For some experiments I need to be able to filter
out blue light with either special light bulbs or a
screen around the bulbs. It seems an orange
coating on the bulb or an orange screen around
the bulbs will do the trick, but I need to filter out
as much blue light as possible. Something like
99% would be good.

Will an orange light bulb do the trick, to filter out
blue light produced by the burning filament? How
can I tell, any specifications to look for when it
comes to orange light bulbs, or any inexpensive
way to test the wave lengths of the light going
through the orange filter or coating? Thanks.

dlzc wrote:
crossposting to sci.chem, and sci.astro. Originally posted only to
alt.sci.physics

On Mar 24, 6:31 am, Fred wrote:
How to filter out blue light?
For some experiments I need to be able to filter
out blue light with either special light bulbs or a
screen around the bulbs. It seems an orange
coating on the bulb or an orange screen around
the bulbs will do the trick, but I need to filter out
as much blue light as possible. Something like
99% would be good.

Will an orange light bulb do the trick, to filter out
blue light produced by the burning filament? How
can I tell, any specifications to look for when it
comes to orange light bulbs, or any inexpensive
way to test the wave lengths of the light going
through the orange filter or coating? Thanks.

You can see roughly what the filter transmission looks like using a
shovelware aluminised CD as a eyeball spectrograph (good enough to see
the Fraunhofer lines in the solar spectrum). Very few yellow or orange
dye based filters will remove all blue light. Lee 767 Oklahoma Yellow or
781 Terry Red comes fairly close with just a tiny leak at 350nm.

If you really want exact control of the cut off and a very strong
rejection of the short wavelengths then a colloidal glass filter for
example Schott GG475 or GG455 depending on where you think blue starts.

http://www.schott.com/advanced_optic...ter/index.html

Regards,
Martin Brown

There is a whole series of sharp cutoff long wavelength pass filters
available in glass as well as gelatin. Their characteristics are in the
OSA Handbook. They range from the slightly yellowish Corning Nonex
formulation to black filters for infrared.

Bill

--
An old man would be better off never having been born.

dlzc wrote:

crossposting to sci.chem, and sci.astro. Originally posted only to
alt.sci.physics

On Mar 24, 6:31 am, Fred wrote:

Will an orange light bulb do the trick, to filter out
blue light produced by the burning filament? How
can I tell, any specifications to look for when it
comes to orange light bulbs, or any inexpensive
way to test the wave lengths of the light going
through the orange filter or coating? Thanks.

Look through a blue filter and if you
see any light, that ain't what you want.
A photographic blue filter would probably
provide the best performance for the lowest price.
I buy custom glass filters, and they are
way more expensive. A filter mass-produced
for photography will be much cheaper.

I wouldn't trust a coated lightbulb to provide
good performance. There are some filters made
for theatrical lighting which provide good
performance at a reasonable cost, if you're
not trying to take a photograph through it.

Also, safelight filters for photographic darkrooms
may provide what you want. They would cut off
blue very strongly. Darkrooms are going the way
of fax machines, wet chemistry, and print media,
so eBay might be the best place to look for them.

dlzc wrote:
crossposting to sci.chem, and sci.astro. Originally posted only to
alt.sci.physics

On Mar 24, 6:31 am, Fred wrote:
How to filter out blue light?
For some experiments I need to be able to filter
out blue light with either special light bulbs or a
screen around the bulbs. It seems an orange
coating on the bulb or an orange screen around
the bulbs will do the trick, but I need to filter out
as much blue light as possible. Something like
99% would be good.

Will an orange light bulb do the trick, to filter out
blue light produced by the burning filament? How
can I tell, any specifications to look for when it
comes to orange light bulbs, or any inexpensive
way to test the wave lengths of the light going
through the orange filter or coating? Thanks.

One other possible solution is high brightness solid state LED units in
red, yellow and green. They are relatively narrowband sources with no
blue at all. The spectrum will be fairly bumpy but that may not matter.

Regards,
Martin Brown

On Mar 24, 8:21*am, dlzc wrote:
... I need to filter out
as much blue light as possible. *Something like
99% would be good.

Look at the spectra of 'cutoff' filters in the Edmund Scientific
catalog. Some have very sharp, near-total cutoff of either red-end or
blue-end radiation.

DB