01-01-2007, 09:15 AM
Join Date: Jul 2006
Location: Twin Cities Metro, North East
Here's where I originally saw the photographic filter over a light meter idea, it's from 1998: Units of PAR
For final measurements and to compare results, as George suggests, I plan to
use a filter over a standard cell (as found in a Lux meter) that is designed
to allow photography in a fluorescent-lighted room with daylight film. That
pinkish/purple filter will give comparison numbers a bit more meaningful for
plant growth, I think.
For that, lux sucks, as does lumens. PAR is actually only somewhat better.
My filter will basically measure relative PAR with a lux meter, even with
different lamp spectra, by de-emphasizing the green part, which most plants
reflect away, anyway.
Wright Huntley, Fremont CA, USA, 510 612-1467