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The Kansas City Star ran an article today (23 March) about CFL and LED
lamps. It starts out with some good points about lumens and color
temperature, and how CFLs compare to LED. It also mentions the
Thanks for the link. However, I am wondering why apparently everyone is
using the Kelvin scale "upside down", i.e. keeps labelling light with
high colour temperature as "cooler", without any further explanation of
this paradox. But when dimming an incandescent/halogen lamp it is
obvious that dim red (low current through the filament) is cooler than
bright white (full current), as well as noon sunlight (CCT about 5500 K
in summer at sea-level) ist hotter than the reddish light during sunset
(you can actually feel the difference!).
The artist's rule "blue=cold" and "yellow/red=warm" may apply to
surface/pigment colours or subjects of paintings (e.g. water vs. fire),
but not easily for illumination. Furthermore, the "warmth" of
illumination may also depend on the color-rendering index: The lower the
CRI the "colder" everything may look, especially if skin color is
rendered unnaturally pale.
BTW, technically, both CFL and LED (irrespective of their colour) have
"cold" light since the radiation is not generated through incandescence
and their spectral distribution is far from being Planckian.