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PAR meter, done really cheap!
I think we all agree that PAR is a better guess at photoactive plant
spectrum than lux.
There is a camera filter that is specifically designed to correct for the
greenish look of CW fluorescents. Their spectrum closely matches the
response of the human eye (10X as much green as red or blue), so CWs are
less than ideal for some plant needs. Unfortunately they give deceptively
high lumens values if you are interested in plant needs.
Used with wide-spectrum daylight-type film, the FL-D (fluorescent to
daylight) filters made by Tiffen, Quantaray, Cokin and others make the final
picture look like it was exposed to broadband daylight. The filter could
reduce the green response enough to make a regular lux meter respond to
different fluorescent spectra much more like a true PAR meter. The numbers
might not be calibrated, but relative values (which is 90% of what we want)
would be quite good, even with different kinds of tubes.
It might be less than absolutely perfect, but I bet it would be a useful
thing to clamp over your lux meter's probe when doing aquarium measurements.
There are a bunch of them on e-bay. You can see a typical one at
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=411613167 . Your
local camera shop surely has or can get them.
Just another idle speculation. I haven't the energy to actually do anything
about it. ;-)
Wright Huntley, Fremont CA, USA, 510 494-8679 huntleyone at home dot com
There are two rules for success in life:
Rule 1: Don't tell people everything you know.
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