Found on the internet and very very interesting to understand light
While LED grow lights are definitely more power-efficient than the old generation of High-Pressure Sodium and Metal Halide bulbs, and will considerably lower your electricity bill, all Led Grow Lights are not standardized and do not represent equal performance. There are literally unlimited variables of wavelengths and ratios that can be employed into a light design, as well as the LEDs themselves and how they are powered.
Some manufacturers claim that their lamps are the brightest, and offer their specifications in lumens. A lumen, however, is a measure of light which is based upon human perception, and not a true, accurate measure of the photosynthetic power of light at all. Indeed, while their light may appear to be bright to us, it might not be bright to plants at all, if the light does not consist of all the precision values plants need to thrive. If a manufacturer advertises their light specifications in lumens, lux or candlepower, beware!
Plants also use many different bands of light for photosynthesis, and some bands of light which, while not photosynthetic to a plant, aid in healthy development, as well as flowering . Some of these photosynthetic and non-photosynthetic wavelengths are nearly outside the human range of perception, and do not seem as bright, even though they are nearly equal in power to the highly-visible bands. If these bands are neglected in favor of LEDs that appear bright to our eyes, plants will not develop correctly. This was a common complaint with early LED grow lamps that used only one or two different values of LEDs, but many manufacturers still design and produce lamps to these outdated specifications.
Oppositely, some manufacturers advertise a full-spectrum, and often include white, green, and yellow LEDs in their design. Many of these wavelengths, however, are inefficiently used by plants, if utilized at all. Plants have three main photosynthetic substances that react best at certain, precise wavelengths of light. When you look at plants in sunlight, most plants appear green, because the bluish-green through yellow-orange spectrum is the spectrum of light which most plants reflect. Reflected light is light which is not used by the plant! To address the use of white LEDs, almost all of them combine certain amounts of blue, red, and green light to produce what we see as white (visual purpose was the reason they were manufactured in the first place), but almost all of these white LEDs use wavelengths of these individual colors that are still nearly useless to plants. Full Spectrum advertisements SOUND good, but they are wasteful of the light you NEED and the electricity you pay for!
LED precision is of the UTMOST importance! If an LED output is even a fraction off of the plants necessary peak value, it can be extremely inefficient for photosynthetic and non-photosynthetic processes. Some manufacturers use less-expensive LEDs that seem close enough to the numerical peak, when, in fact, their chosen values may need up to 10 times (or more) as many LEDs to do what ONE LED of peak-value efficiency will do! ProSource Worldwide has scoured the globe to find the EXACT peak values that plants utilize. Only right on is close enough for us! (And it should be for you as well!)
As you shop, you will also notice that some manufacturers advertise that they are using 5 and 10 watt LEDs in their products. While these LEDs are certainly showy and brighter than their 1 and 3 watt counterparts, they are also very power-inefficient. Higher-wattage LEDs create more heat, so much of the electricity they consume goes toward the manufacture of that heat, and the sad truth is that they do not put out nearly the proportion of light to the power consumed as the 1 and 3 watt LEDs. Depending on LED manufacturing differences, some 5W LEDs put out LESS light than the best 3W LEDs! (Also, it should be noted that, for the wavelengths of light plants can best use, very few of these wavelengths are available in LEDs rated higher than 1 and 3 watts!) Ironically, products that use higher-wattage LEDs to produce the same amount of light as 1W and 3W-based units are also much more costly to manufacture, and that cost gets passed down to you as the consumer many times over: once at the time of purchase, and again, every time you pay your electricity bill!