Re: CFL Color Temperature

In <k237r3l14mitcjlpk2erhh0fadvoqfr2cv@xxxxxxx>, V. Roberts wrote in part:

Well, there is some physics driving the high CCT of CFLs. As
you know, in normal fluorescent lamps the mercury produces a
bit of blue and green light that is mixed with the slightly
yellow light from the phosphor to make white.

It turns out that the current density in most CFLs is so
high that they generate a lot of blue light. So much in
fact that many CFLs use only a two-component rare earth
phosphor mix instead of the normal three-component mix.
There is just too much blue to have any more coming from the
phosphor. (If the phosphor does have all three components,
then the blue component is reduced in small diameter lamps.)

Somehow I see either 3 or 4 phosphor bands/features in the spectra of
CFLs and "triphosphor" T8 fluorescents, Philips "Ultralume", etc. Could
two of these spectral features be from the same phosphor?

What I notice, in order from longer wavelength to shorter:

1. The strong orange-red linelike extremely narrow band around 611 nm,
along with some very weak similarly narrow bands nearby from yellow to
deep red,

2. a small group of wider but still very narrow bands in the green, with
the dominant feature maybe typically around 542 nm,

3. a dimmer, moderately narrow band in the green-blue/blue-green
with its brightest part around 485-490 nm but extending into the
blue-green around 500 nm, and

4. a wider still blue band, that with CFLs I usually only see when
nominal CCT is at least 3500K, mainly from 440-475 or 440-480 nm or so.

- Don Klipstein (don@xxxxxxxxx)
.

Relevant Pages

  • Re: CFL Color Temperature
    ... So much in fact that many CFLs use only ... coming from the phosphor. ... a small group of wider but still very narrow bands in the green, ... moderately narrow band in the green-blue/blue-green ...
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