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Re: Lights



Gary (MStark7789 at aol_com) wrote:
> So in order to actually increase the light in a
> given area 
> should
> I look for a bulb with a higher CRI or Lux rating? Unfortunately the
> only 
> thing I have
> to test this with is a camera photometer. Fluorescent light does
> strange 
> things to
> it especially at close proximity to the source..If you pass it under
> the tube 
> it
> shows the brightest area to be about 5 inches from either end of a 48
> inch 
> tube
> growing dimmer toward the center and then increasing as it gets to
> the other 
> end.
> Don;t know  to believe this or not as it looks the same to my eyes.
>                                          Thanks again   Gary
> 
> ------------------------------
Maybe I misunderstood your question.  CRI (color Rendition Index) is
measure of how well colors, when viewed by humans, under a given lamp
will seem normal -- I think "normal" is standardized on tungsten bulbs.
 Plants don't prefer the same colors as humans anyway.  So a higher CRI
doesn't mean the bulb will yield more light that your plants like.

Lux is a measure of light output.  It's the International System unit
of illumination, equal to one lumen per square meter.   Roughly
speaking, a lumen is a unit of light of one candela on one square meter
of surface, the illumination of which is uniform.  A candela is the
unit of luminous intensity equal to 1/60 of the luminous intensity per
square centimeter of a blackbody radiating at the temperature of
solidification of platinum (2,046K). 

More bulbs close together will add more light.  More lux will add more
light but not necessarily in the frequency range that plants like.  A
good rule-of-thumb is to stick with bulbs designed for plants, like
triphosphor flourescents or metal halides.

RE your light meter, it might be sensitive to certain wavelenths, which
might not be radiated as strongly at the center of your bulbs.  Your
eyes may be less sensitive to those wavelengths.  For example, the
meter might be sensitive to infra red or ultra violet, but your eyes,
like mine do not see.  The light meter's manufacturer (owner's
manual?)can probably tell you what frequencies it is sensitive too.

If you want a little tiny bit more light, get a more efficient bulb
that emits more lumens (hopefully in the range plants like).  To get a
lot more light:

1) add more bulbs in parallel (or otherwise positioned to shine on the
same area of the tank.)

or 2) change to a different kind of lamp.  Change from normal
flourescent to VHO flourescents or to Power Compacts, or change to
metal halides.

Does that help?
Scott H.

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