[Boatanchors] CFLs

[Richard Knoppow]

----- Original Message ----- 
From: "Bob W5UQ" <W5UQ at att.NET>
To: <boatanchors at mailman.qth.net>
Sent: Saturday, January 01, 2011 7:45 AM
Subject: Re: [Boatanchors] CFLs


> has anyone, and I haven't read ALL the threads, addressed 
> degrees Kelvin
> and color temperature with the lamps?
>
> 2600 degrees K is more like sunset light... lots of 
> yellows and reds.
> 5000 degrees K is more like hot sunlight... more white and 
> less yellows
> and reds.
> Actually HOT over head sun gets as high as 15,000 degrees 
> K.
> By the way.... WHITE in light is the "presence of all 
> colors".  The
> whiter it is, the wider the freq spectrum and balanced 
> spectrum.
>
> More trivia or interesting "stuff":
> Food prepared in a kitchen with 2600 to 3600 degrees K is 
> "more pleasant
> to the eye"... hence, candle light dinners are more 
> romantic.
> Food prepared under 5000 degrees K (daylight) isn't as 
> pleasant and
> doesn't taste as good...  (psychological):-)
>
> Most people don't even realize the differences UNTIL they 
> see the lamps
> side by side.
> Then the 3200 degree K lamp turns red/yellow next to the 
> daylight 5000
> degree K lamp.
>
> My pet peeve is that they do NOT print the degrees K on 
> the lamp boxes
> sometimes.  AND then they like to attach names to them 
> like daylight and
> soft white.
> I get the daylight, but what is soft white?  Soft white to 
> one
> manufacturer is probably one thing and different to 
> another.
>
> Due to your CFL email threads, just seeing bunches of 
> them, I realized
> that I could not see the rigs on my work bench as good as 
> I needed.
> I've kept an LED flashlight there to look at parts closer, 
> etc. :-)
> So when I found some OLD work lights in the garage, that 
> used screw in
> incandescent lamps,  I got an idea.  I got two 75 watt 
> (apparent light)
> daylight CFL's and replaced the old fashion yellow/red 
> bulbs.
> I clamped the two worklights onto my test eqpt shelf right 
> above the
> gear.  BOY... I can see now.  Well, except for a bit of a 
> glare...so I
> have repositioned the fixtures a bit...
> But you guys gave me the idea...  THANKS GUYS....
>
> Wonder why my old brain didn't figure that out earlier... 
> hee hee.
> HNY......
> Bob Hardie  W5UQ
> retired and having fun
>
> and the beat goes onnnnnn!
> W5UQ.com
> A25UQ, V31UQ&  VP2EEU
> QRZ.com is accurate for all.
>
     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