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[APD] Re: Light measurement terms

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.


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:


Scott H.

Wright Huntley -- 760 872-3995 -- Rt. 001 Box K36, Bishop CA 93514

           Mencken's maxim—every election is a sort
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