Re: [AGA Member] Re: help about fluorescent bulb

["S. Hieber" <shieber@yahoo.com>]

CRI is a subjective index that represents the degree to
which the color of objects illuminated with the device will
appear as they they due under "normal" light. A standard
incandescent bulb will have a CRI of 100. A good PC bulb
might be in the 80s -- and that's fine.

Color temp is rating that indicates the overall color ofhte
light. A bulb with a high narrow blue peak and a broad
lower red peak will have the same color temp as a bulb with
a broad lower blue peak and a hig narrow red peak. Two diff
bulbs withthe same color temp rating can appear very diff.
The only good assessment of the spectral output of a bulb
is a graph that correlates the amount of output with
frequency.

As a rule of thumb, the higher color temps appear more
bluish. The lower color temps can appear more reddish,
yellowish, greenish. . . .  You need to compare actual
bulbs or buy from a supplier that chooses good bulbs -- if
yoy do that, your plants won't much care which bulbs you
buy -- I beg off, however, on the issue of redness, which
seems to be very much in need of sorting out.

What plants prefer re bulb color temp ratings is a bit more
vague except that in general, plants are more senstive to
the color frequencies that Humans are less sensitive too
and vice versa. A bulb that looks brighter than another to
us might seem jsut the opposite to plants.

The output of a fluorescent bulb isn't jsut a matter of
what phosphors are used but also the amount of impurieties
in them.

Scott H.
--- Dennis Sheridan <dilvish@pacbell.net> wrote:
> ----- Original Message ----- 
> 
> I'm curious about CRI - color rendering index. I can see
> the obvious
> difference in what my eyes appear to see at 10k as
> opposed to 6.7k.
> I understand, I think, that much of this is due to the
> phospers that
> different bulbs use (in that some bulbs have a lower cri
> rating than
> others). I assume it is important to select bulbs with a
> high CRI.
> Does it necessarily follow that high CRI gives you a
> closer
> approximation to "true color", whatever that may mean?
> 
> If 6.xk approximates (to a plant) noon day sun, and 5.xk
> mid-morning, that would mean that our plants are always,
> when lights
> on, in either mid-morning or noon sun. Does this need to
> be taken
> into account in terms of dosing, hours, algae control,
> etc..  or am
> I overcomplicating?
> 
> -d
> 
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=====
S. Hieber

-  -   -   -   -   -   -   -
Amano Returns
to the AGA Annual Convention
Nov 2004 -- Baltimore

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