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halogen lights


>> Do you know the PAR
>> rating?

Why don't you humour me and just tell me
the PAR rating of the lamp if you know
it.

> It just takes five times as much
electricity to get the same
>number of photons to the plant.

Are you not contradicting yourself here?
If it takes 5 times as much energy to
get the photons to the plant wouldn't
they be 1/5 as efficient as fluorescents
and not at least a half as efficient.
Which is it? How did you come up with
the 5 times number? Do you have any
numbers for the things like how much
electrical energy is converted into
radiant energy or what percentage of
that falls within the 400 to
700nanometer range.

>That higher lumens/Watt rating misleads
>people into thinking it may be better.
It often is not.

Then why refer people to an article that
makes lamp comparisons based on their
lumens/watt.

>It has more to do with the subject at
hand than your posting, IMHO. It
>explains the visual spectrum and gives
comparative efficiency ratings of a
>wide range of sources. It also lists a
lot of useful resources.

My posting is that knowing the luminous
efficiency of a light source is very
misleading. The article makes no
distinction between luminous efficiency
and input watts/output watts efficiency.
It does not even mention plants.

>Glancing at the contents, it looks like
a good primmer for the truly
>uninformed. I may have been mistaken in
assuming that most of the regular
>readers knew a little basic science.
The Lancaster article summarized
>answers to a couple of questions that
tend to recur here frequently. It
>assumes slightly better science
knowledge than is usually imparted by
the
>mandatory government school system. I
agree on that.

I think you are trying to insult me here

>> In plant growing Lumens/watt can
>> be used to measure system
efficiencies
>> but has almost no bearing on the PAR
>> rating of the lamp.

>That's a strong statement. They are
very *closely* correlated for most
>lights, and only really come apart for
lights whose spectrum has been
>efficiently tailored to human scotopic
sensitivity -- for example, CW
>fluorescents.

As you know the lumens rating is so
heavily weighted toward the green that
the red and blue areas become
insignificant. I  think that the
corelation between lumens/watt and and
photons/watt is mostly accidental. It
happens only when the area of the green
spectrum is representative of the whole
spectrum. P and A lamps and CW lamps
have very different lumens/watt
efficacys, the P and A lamps are rated
at almost half the CWs and yet which is
better for growing plants. They are
about the same as far as I can tell and
so are their PAR ratings. That is is
mainly why I like the idea of rating
lamps in photons per watt the rating is
not just good for some lamps but for all
lamps regardless of what the way that
they produce light.

>> As usual
>> there is no usable information in the
>> article such as radiant power
efficiency
>> of various lamps or calibrated
spectral
>> power curves it is all just the usual
>> hogwash.

>Those are generally available from the
manufactureres, in their catalogs,
>and were not the subject under
discussion (halogen suitability).

But I am saying halogen suitability
cannot be determined without knowing
this stuff. Maybe when I get to heaven
the lamps will be rated in photons/watt
but I hope I do not have to wait that
long.

Wayne Jones

Wayne's DIY Aquarium Setup at
 http://www.mnsi.net/~waj