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In article ,
(N. Thornton) writes:
Dave Plowman wrote in message ...
In article ,
N. Thornton wrote:

I would not recommend anything as high colour temp as that for
domestic use. 4500K is going to look terrible, and 4700K a shade
worse.

Depends whether you want to retain the accuracy of the colours on your
monitor - although this depends on what colour temperature it's designed
or set up for.

Tubes like that look terrible under all conditions. Cool white is the
tube that gave fluorescents such a bad name, and 4500K is quite
similar to cool white, being nearly as nasty. The only exception I've
found is with extremely low powers, like 2w, which give an icy moonlit
nightlighting effect.

A lesson in colour temperatures might be handy here...
Your eyes and brain were designed to work with natural sunlight.
Sunlight has a very wide range of colour temperatures and intensities.
The midday summer sun can be 6000-8000K and very bright. Conversely,
sunset can be less than 2500K and very dark compared to midday summer
sun. However you can still see colours fine in both these environments
as your eyes and brain are evolved to work over that range.

Now what screws things up is if the colour temperature is way out of
range for the light level (lumens). Artificial lighting levels people
use in their houses are actually not a lot brighter than sunset, so
the colour temperature most appropriate is around that of a filament
lamp at 2700K. (You might argue that given a filament lamp is 2700K,
people have chosen lighting levels so that looks 'right'.) This is
also the colour temperature of most compact fluorescent retrofits so
they match filament lamps and your expectations of colour temperature
of artificial lighting.

For lighting during the daytime, you will expect higher light level,
e.g. in an office. To match a higher light level, you would also
expect a higher colour temperature. This is why offices normally use
3500K colour temperature lamps. If you intend to light a room in
your house particularly brightly (maybe the kitchen or a workshop
where you do intricate work), you might prefer 3500K lighting there,
but it will seem a bit strange initially when you walk in to it in
the evening, although you will adjust to the higher lighting level
and colour temperature in a matter of seconds.

Now the very high colour temperature lamps (~5000K and up) will look
perfectly OK if you fit enough of them that you get up to midday
summer sun lighting levels. That probably means completely covering
the ceiling with the fittings. Remember what happens if you take a
sheet of white paper out into the summer sun -- you have to squint
to read it the light level is so bright, and even after time to
adjust to the lighting level, it won't be comfortable reading it.
Now you will have to get your artificial lighting up to that same
uncomfortable level before these very high colour temperature lamps
will feel right. Why you would want to do this I can't imagine.

Another area confused with colour temperature is the nature of the
spectrum a lamp emits -- continuous at one extreme and a few discrete
lines at the other. This is completely unrelated to colour temperature,
but unfortunately the lighting industry marketing people confuse the
issue for using terms which imply a continuous spectrum when they
really mean high colour temperature. The two properties are not
related. Descrete line sources, or sources which are continuous but
are not even or have some holes/peaks in the range can cause colours
to be washed out, simply because they happen to be missing some of
the components a particular pigment responds to, of have an over-
abundance in some part of the spectrum. Generally your eyes are
quite forgiving of descrete line light sources, providing there are
enough lines covering the visible spectum and they are not too badly
matched. TV cameras and anything else which splits an image up into
colour components and reassembles it at the other end can be a lot
less forgiving though.

--
Andrew Gabriel