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Re: Filtered light
David Bundy asked about using some sort of filter to alter the output of a
cheap bulb in an effort to match a more expensive, full spectrum bulb.
It can't be done.
All filters, cheap or expensive, work by absorbing (removing) part of the
light energy which passes through them. There are no filters which will ADD
what isn't there in the first place.
Cheap CW fluorescent tubes have a strong output spike in the area we humans
perceive as green (as Ivo says, around the 550 nm region), with little or no
output in many other regions. If the energy isn't there to start with, the
filter cannot add it.
GE Chroma 50's are not expensive (at least not in North America) and provide
a spectrum which most of us who have used them seem to feel is adequate for
aquatic plants. I'm sure that there is an easily available European
equivalent to this tube.
James Purchase
Toronto