End of the lighbulb in Europe

Started Mar 10, 2007 | Discussions thread
Joseph S Wisniewski Forum Pro • Posts: 35,734
"Reveal" bulbs not "color corrected"

Glen Barrington wrote:

HOWEVER, General Electric sells color corrected general purpose
tungsten bulbs that I prefer to use for my computer workstation.
The brand is the GE Reveal line

Welcome to the slimy side of lighting...

Neodymium glass bulbs like the GE "Reveal" or "Enrich, the Philips "Natural Daylight", the Sylvania "Daylight", the "Chromalux" and "Pure Lite" brands are not color corrected", at all. They actually have a pretty low CRI (color rendition index) of about 70. Plain old clear glass incandescent bulbs, like sunlight, have a CRI of about 100. You cannot judge color anywhere near as accurately under a neodymium glass bulb as under a clear glass bulb. GE promotes them as more "natural" because they have a higher color temperature than clear glass bulbs, despite the lower CRI.

Unscrupulous bulb mongers push these horrible bulbs at many different groups. They got you (like the get painters and seamstresses) with a false promise of being able to judge colors more accurately. Some promote them as "full spectrum" or a "healthy" light. Others promote them as more efficient. Some market them to promote the health of pet lizards and birds. All these claims are, simply, false.

Neodymium glass has a "wild" spectrum full of peaks and valleys. There are more and bigger valleys in the lower frequency colors (red, orange, and yellow) than in the higher frequency bands (violet, blue, and green) so the overall effect, aside from the degradation of CRI, is an overall raising of the color temperature from a clear bulb's 2900K to anywhere from 3200K to 4100K (depending on how you measure it, because color temperature meters don't work well on neodymium bulbs, and you really need a spectrophotomiter to compute the CCT, correlated color temperature).

Although that's warm enough to appear "warmer" than a regular incandescent bulb, it's not warm enough to approach "daylight" or give you much of a daylight feeling.

Neodymium bulbs, like any other incandescent colored glass bulbs (including "party lights", "bug lights", and incandescent "blacklights") are also more dangerous than clear glass incandescent bulbs. The glass absorbs more energy and therefore the glass and metal run hotter than a more conventional bulb, increasing the risk of fire and explosion. And, like any color filtered bulb, they're less efficient (less visible lumens per watt) than an unfiltered bulb.

We "off hand" (furnace and big metal "blow pipe") glassblowers sometimes wear neodymium glass safety glasses because that big yellow "hole" in the spectrum cancels the yellow light emitted by hot sodium. Glass is "fluxed" with sodium, so the neodymium hole lets us judge the color of hot glass better. The "other" glassblowers (lamp workers or torch workers) who actually spend a great deal of time with rods of glass stuck in a flame, find the neodymium blocks the bright yellow "sodium flare" and really reduces fatigue.

Actually I prefer them for everything.

Yes, they're quite like an addictive drug in that respect. Because of all the holes neodymium glass leaves in the spectrum, it has an interesting effect on many common colors. Reddish and greenish colors often have a considerable yellow component in their spectrum. Mixed with red or green, this tends to make the colors more "brownish" or less saturated. Elimination of the yellow component adds an unrealistic "pop" to colors. Lipstick looks more saturated, skin looks less "sallow". I like them in my bathroom, and the fixture will take the heat of six 60w globe neodymium bulbs.

Plants and flowers also look more "vibrant": with the common yellow pigment blocked, there's more differentiation between red and green. That's why Tiffen, Hoya, B+W, etc. make "enhancing" filters from neodymium glass.

but I can't find anything close to a color corrected
flouresent to replace regular 'bulbs', when those are available, I
will go totally flourescent.

You can get high CRI compact fluorescent bulbs (in fact, that's a good thing to Google, "high CRI compact fluorescent"). Even ordinary CF bulbs typically have a better CRI than the neodymium bulbs you're using now, and are a much better choice for your computer lab. My work area is lit by Philips fluorescent bulbs with a respectable CRI 98. They're 4 foot, 32W, T8 bulbs, two to a fixture.

You'll also often hear neodymium referred to as "didymium", because it naturally occurs together with another rare element, praseodymium. For coloring glass, the praseodymium is separated out and discarded.


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Ciao! Joe


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