[Coral-List] PAR intensity of different kelvin globes

Steve Dalton sdalton at nmsc.edu.au
Thu Aug 10 22:53:19 EDT 2006

I recently purchased two 400watt metal halide lights and two what I assumed 
were 14000 kelvin globes to conduct some coral bleaching experiments on 
subtropical hard corals.  After setting up the experiment I was not able to 
get consistent PAR intensity across all temperature treatment so I had to 
purchase another 400 watt light.  The problem was that the globe that were 
provided with the additional fitting appeared more blue than the original 
globes and when I measured the PAR intensity output of the three individual 
lights the two globe which were first purchased were nearly twice the value 
of the more blue light.  The supplier indicated that the third globe was a 
different brand and so sent another globe that was the same brand as the 
first two.  This did not solve the problem because the new globe was still 
noticeably bluer than the original ones and the PAR output was still 
considerably less.  Could it be that the original globes were a lower 
kelvin value say about 100000K which would explain why they were less blue 
than other globes?  Or the more blue globes are 200000K and marked 
incorrectly.  Does anyone know how I can tell what kelvin rating these 
globes are and whether PAR intensity decreases with kelvin rating when the 
globes have the same watt rating?
If anyone can help me regarding these question I would really appreciate 
your comments


Steven Dalton
PhD student
University of New England
NMSC Postgraduate Representative
National Marine Science Centre
Bay Drive, Charlesworth Bay
(PO Box J321)
Coffs Harbour, NSW Australia 2450
Ph: 6648 3928
Mob: 0432 946 782
sdalton at nmsc.edu.au

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