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Re: [APD] Re: Light measurement terms

It seems that most of the light questions are:

how much light should I have,
what color bulbs should I get,
and are these brand such and such bulbs any good.

I think that folks that are going to ask APD instead of
searching out these pages themselves are not going to get
much help from  defs that delineate psychophysical from

But I was only offering it as one more on the list, not the
definitive place to go.  I had a few others too, but got
tired of typing and lots of others have already been

It's good that you point out the shortfalls of this page.

The main thing that I thought was useful about it was the
audience to which it is geared and the diffs between lux
and lumen.

Probably the least available info for most folks is the PAR
out put of bulbs/lamps.

As for useful, I think you end up back at wpg; I've said so
for a long time, and why.  ;-)

a penny back,
Scott H.

--- Wright Huntley <whuntley at verizon_net> wrote:
> I consider this a particularly unfortunate page to send
> folks to, Scott. 
> It has some decent "illumination" definitions, but no
> really useful 
> "light" measurement terms at all!
> It totally confuses (i.e., fails to clearly delineate)
> the essential 
> differences between units for measuring light energy
> (radiometry) and 
> psychophysical units for measuring observer-apparent
> illumination 
> (photometry).
> [The latter have minimal utility for plant purposes, and
> are, in some 
> cases, the exact opposite of what is needed. All but 2 of
> the site's 
> definitions are pure psychophysical units defined only in
> terms of a 
> standard human observer's eye, but that is never even
> mentioned, there.]
> That distinction (radiometric vs photometric) has seemed
> to lie at the 
> root of about 95% of the illumination/power questions
> that we have seen 
> confusing folks on the list. No?
> Just my US$0.02.
> Wright
> > Message: 1
> > Date: Fri, 17 Oct 2003 04:49:40 -0700 (PDT)
> > From: "S. Hieber" <shieber at yahoo_com>
> > Subject: [APD] Light measurement terms
> > To: Aquatic Plants Digest Messages
> <Aquatic-Plants at actwin_com>
> > 
> > Here's another page with some decent definitions of
> light
> > measurement terms:
> > 
> > http://www.ledtronics.com/pages/tech4.htm
> > 
> > Scott H.
> -- 
> Wright Huntley -- 760 872-3995 -- Rt. 001 Box K36, Bishop
> CA 93514
>             Mencken's maxim?every election is a sort
>               of advanced auction of stolen goods.
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