The typical rating most growers are familiar with is the “lumen.” The definition of the lumen is the total light produced within the range of the human visual response. It tells us nothing about the distribution of that light energy over the spectrum, and most importantly, it doesn’t tell us how much is useful for plants.
The problem with lumens is especially pronounced when measuring light at the far ends of the human visual response curve. Consider three lamps—red, green and blue—each emitting the same number of watts of optical energy. The red and blue lamps would have much lower lumen ratings compared to the green lamp, simply because the human visual response is very low at red and blue, and highest at green. That’s why a high lumen rating does not necessarily make a lamp better suited to growing plants.
Similarly, light meters that measure in “lux” tell us very little about a lamp’s plant-growing power. The light sensors in lux meters have their own spectral response curves which may over- or under-measure light at various colors. This is why lux meters usually have different settings for “sunlight,” “fluorescent” and “incandescent” lamps. Again, because lux meters are meant for measuring the amount of light usable by humans, they don’t tell us anything about how plants will respond.
Plant biologists define light in the 400nm to 700nm spectral region as “photosynthetically available radiation,” or PAR. The unit for measuring PAR, micro-mols per second (μmol/s), indicates how many photons in this spectral range fall on the plant each second. Inexpensive PAR meters use sensors that respond over the entire 400-700nm spectrum, and have their own sensitivity curves that require different calibration for sunlight, fluorescent and HID lighting.
the link you provided would work but if you want to get serous you should get 2 of em and hang em in a an inverted V like /\ mine has 3 but you'll get the idea from the pic View attachment 3176823
