Originally Posted by Hoppy
The acrylic lid attenuates the meter reading from 99 to 89 lux with it sitting on my desk and the overhead CFL light lighting the room. That would be a 10% loss due to the lid, which would just change the conversion factor from 60.6 to 67. Not a problem, that I can see.
There is a tiny "instruction manual" with the luxmeter, which has this chart on it:
Clearly this is not consistent with a true PAR meter, but calibration against a PAR meter for specific light sources should take care of this easily enough.
The scale is no good.
What you need to do is compare the PAr meter to this meter once it's set up and done.
Then see how the readings compare and then use that difference for the factor.
I suspect most of the typical white FL bulbs will be somewhat close as far as a PAR to Lux comparison.
Put another way: some standard measure of light is better than NONE.