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Chroma 50 vs. Vita Light

Date: Wed, 27 Jan 1999 02:26:46 -0500 (EST)
From: "Richard J. Sexton" <richard at aquaria_net>
Subject: Chroma 50 vs. Vita Light


>It may be a diminished return, but there are serious differences in the
>actual spectrum of the tube.  I've looked at both through a diffraction
>grating (Thanks Wright!).  The Chroma-50 is essentially a tri-chromatic
>tube with not a lot of power in between the spikes.  The vita-lite has
>some trick for "smearing" more of the color in between the peaks, which is
>why it has such as high CRI.
>Personally, I use the cheaper tubes now, because I can't see the point of
>spending an extra $10 US ($15 CDN) either.  Just saying there *is* a
>difference in the actual tube.

Huh. In that case GE is lying on their pretty little graphs. 
They show it as quite a flat spectum. We end to bug Wright
to snap a few piccies of this. I see a collection of these
on the web in my crytal ball.

How's about it Wright? It's your pennace for all those mutant

I assumed the original post just contained a mistake. "Chroma-50" and
"daylight" tubes have always been continuous-spectra tubes, AFAIK. The
"daylight" is a little more biased toward the blue, and the C50 to the
red end. Together they make somewhat dim-looking but fairly nice white
light with lots of photosynthetically active light. Very smooth spectra,

I've never seen one with tri-phosphor-like spectral spikes.  There is
nothing wrong with those, BTW, for they do wonderfully in those tanks
where I use the cheaper compact flourescents. The absorption spectra of
the active plant pigments seems broad enough to use the narrower spikes
quite well. Maybe GE got a little loose on their labeling process? IDK.

Sorry, Richard. Pics don't hack it, and I'm too lazy to dig out my
little 1/4M Jerrel-Ash monochrometer, and run actual spectra (without
getting paid for it). Pics have two uneven responses involved. One is
your perception of color (you can't see 60% of the most useful stuff)
and the film's response (it probably misses a lot, too).

Mutant fish? No comment, but a bit of optical fish trivia:

Did you know that some desert pupfish of the genus *Cyprinodon* have
chromatophores that they can "flash," just like rainbowfish, to attract
a mate to spawn?

Now you know. ;-)


Wright Huntley, Fremont CA, USA, 510 494-8679  huntley1 at home dot com

Liberalism is totalitarianism with a human face.
                                  Thomas Sowell