Many people express frustration about the difficulty in judging how much light they have, and the $300+ cost of buying a PAR meter to measure the light. We now have some options to spending that much.
We are hobbyists, not scientists, so we have no reason to want a "perfect" PAR meter, or even the best available PAR meter priced under $1000 - the Quantum PAR meter. As long as we can determine that we have 20 micromols of PAR and not 50, or 40 and not 80, etc. we can benefit a lot from cheaper PAR meters. Now there are two threads in the DIY forum that describe how to make your own PAR meter cheaply: Convert Lux meter to PAR meter?
and DIY PAR meter, Yeah you heard me
Some people don't feel competent doing DIY projects like this, so both of these DIY PAR meters are or will be available, in limited quantities, for limited times, to buy on the Swap n Shop forum.
The first of those two DIY threads is mine, and the last post asks that if you would be interested in buying one, at cost, no profit, just PM me. The other thread already resulted in some being sold to members here, with more to come later.
With either one of these you can evaluate your own lighting, adjust the height of your suspended light to get the light level you need, figure out why why can't seem to get rid of algae, or why your plants don't seem to ever grow, etc. And, you can add to the accumulation of PAR data for many more light fixtures, making the decision about which light to get much more accurate.