That is cheap
I am saying that you can not accurately compare different fixtures with different spectrums using a PAR meter
Why are you saying this might i ask?
A par-meter reads only what the plants see.
A sphere reads only the total out-put.
I don't know the range used to measure photon output in a sphere? My par-meter is picking up outside the normal 400-700. Reads 300-1100nm. 300-810nm, all used by the plant & will be incorporated in the newer leds coming out. At least 385-730nm anyways. If you have a rough idea of a decent spectrum then you should not be betrayed by the par-meter.
I'm sorry if you have been miss-informed by GG's or whomever. But there is a reason Shane from Mi-Gro compares fixtures using the Flat-Intigration method or par-meter & ppfd. Where all those #'s land on the canopy makes the big difference too as well as spectrum. Hot spot on not spot?
Hence the importance of seeing the Par-Map itself so you know if that fixture works for your space. Do you want spread or central light source? Ceiling height plays a big role as well as plant growing techniques to make this decision.
All things a Shpere will not tell you.
Don't get me wrong, it deffinetly has its place. Like for instance, a sphere will provide the efficiency ratings needed for a tax deductions from Energy Star or however it may work in some places for commercial growers. Total output vs canopy input basically. Both useful. One more so in the garden then the other.