Re: [APD] light PC/HPS

[Thomas Barr <tcbiii at yahoo_com>]

>  I was asked a question that I have no idea how to answer but
> I bet a
> gazillion of you can answer.  I was asked about the relative
> plant growing
> efficiency of power compact fluorescents (i.e. the ones in
> something like a
> Coralife fixture) vs HPS -- in other words if you had 250
> watts of each type
> which would:1) waste the most energy as heat and 2) grow
> plants the fastest.

1. PC's will
2. HPS will

As a rule.....but there maybe some brands here and there that
are a little better etc.

PC's will look better and offer more color temp options, the
spread of light is also a big issue on the footprint of the
growing area. 

HPS look pretty bad to our eyes.

HQI's are better I think to get an even appearance to our eyes
without losing much watt/PAR.

I'm probably the only person(or one of the very very few) that
has a PAR meter and uses it on aquariums for FW plants.  
It's also calibrated for electronic sources or Sunlight.

Measuring the intensity at a single point is not a fair
comparison using a meter, you need to measure an area to get a
better idea since one source is a long linear section and the
other is a point source.

Plant leaf morphology also will play a role, distance from the
light etc etc.

Many issues in measuring light, all in all, it's not easy even
for feeble minded plant scientist.

I've used HPS and PC on the same tank about 8 years ago or so. 

Regards, 
Tom Barr 


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