using blue photodiode for PAR
 

I would like to make a number of small sensors for a plant study for use
with a 0-5v data logger, that would somewhat approximate a PAR quantum
sensor.

There are a few small good quality blue photodiodes available that
approximate the spectral sensitivity curve of the human eye 400 to 700 nm
(centered near 555nm or so). The Sharp BS520 from Digikey is an example.
But PAR supposedly has very sharp cut-offs at 400 and 700 nm, but otherwise
flat from 400-700nm. .

Can I correct the spectral curve of one of these blue photodiodes using
Kodak color compensating gels (some call them Wratten filters) and have some
success? My overlays of the filter charts would indicate that using both a
CC50R (red) and a CC50B (blue) together in front of the diode would just
about do it.

Does anyone see any big problems with my reasoning with this. I don't have
equipment to analyze the photodiode/filter combo, but DO have access to a
Quantum sensor to compare.

Thanks
Jim