[Boatanchors] CFLs

[J. Forster]

Xenon is not a Black Body radiator either. It has a number of lines,
including a whopping NIR peak around 900 nM. That peak is a very good
match to silicon detectors.

-John

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>      FWIW, color temperature stated as K is, in a strict
> sense applicable only to black body radiators or objects
> approximating them. That is to something with a continuous
> spectrum of radiation. Sunlight and tungsten lamps are close
> enough. Fluorescent lamps are broken spectrum radiators so
> the best that can be said is that one is _visually similar_
> to a black body radiator at a given K. Even so, as has been
> pointed out, the colors perceived under such light may be
> quite different than those seen under a continuous spectrum
> since some dyes and pigments may reflect only narrow bands
> of colors. For instance some red objects will look brown or
> black under some kinds of illumination although they look
> fairly white to the eye. Flourescent lamps work by using a
> mercury or other gas discharge to excite a mixture of
> phosphors. It is mostly the output of the phosphores which
> is seen. By chnoosing the phosphors correctly a lamp
> simulating a wide range of color temperatures can be
> approximated but the illumination is never quite the same.
> For this reason fluorescent lamps are usually designated by
> such general terms as Daylight, or Warm-White rather than by
> K. Most household incandescent lamps are right around
> 2900-3000K, the standard color temperature for studio lamps
> is 3200K, old style photo-flood lamps are 3400K. This is
> about as high a color temperature as is possible for a
> tungsten lamp since the life of the lamp becomes very short.
> Average daylight is around 6500K, this is a mixture of
> sunlight and skylight and is the standard color for
> television white. Direct sunlight is assumed to be around
> 5400K and lamps of around 5000K are standard for evaluating
> color for graphic and other purposes. For theater projection
> the old standard was 5400K, which is available from
> high-intensity arc lights. Nearly all theater projection now
> uses Xenon arcs, which have a higher color temperature.
>      Since the eye adapts to variations in illumination
> color rapidly all illumination in a room used for color
> evaluation or color matching should be exactly the same
> color.
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com