Quote:
Originally Posted by Richard
Yes exactly.
You seem to have a misunderstanding of "spectrum". LED's produce single frequencies. Sure you can gang up LED's at say, 5nm intervals but still in physics we would never consider that a spectrum. Instead, it is a series of point frequencies. This is why the graph you provided for the "typical spectrum of a household LED bulb" is incorrect. An accurate graph (or measurement) would be a series of vertical bars with no lines connecting frequency point to frequency point.
Now since PAR is a measurement of fitness (similar to least-squares) of one spectrum to another it is completely inapplicable to LED sources.
Further, I have never recommended "a household fluorescent" for plants -- nor would I. Instead I've specifically recommended 6500 Kelvin bulbs installed at a power density of 1200 Watts per square meter of projection -- the projection surface measured one meter from the source.
With regard to lumens, it is measured by flux of the green portion of the spectrum which plants do not use. So "more lumens" never means anything of use for judging benefit to plants. However, I noticed the term lumens is highly touted in head shops.
|
You are dead wrong and you pontificate without presenting verifiable references which I consider unethical.
Technically, household LED bulbs are fluorescent but we don't call them "fluorescent" to avoid confusion with traditional fluorescent bulbs. Traditional fluorescent bulbs are coated with phosphors that convert ultraviolet light to longer wavelengths. Similarly, household LED bulbs contain blue LEDs that are coated with phosphors that convert part of the blue light to longer wavelengths. See
https://en.wikipedia.org/wiki/Phosphor#White_LEDs
And, note that unlike you, I present verifiable references to back up my statements.
And, you can buy chips consisting of blue LEDs coated with special phosphors just for growing plants, e.g., see
100W 50W 30W 20W 10W 3W 380NM-840NM Full Spectrum High Power LED Chip Grow Light | eBay
Here is the spectrum on the left (ignore the one on the right because it is wrong):
Incidentally, the most efficient light sources that you can buy (as opposed to a laboratory curiosity) are blue LED chips which are about 52% efficient (watts/watt). In contrast, a traditional fluorescent bulb is typically 22% efficient. See
https://en.wikipedia.org/wiki/Fluore...inous_efficacy
and note:
"whereas typical fluorescent lamps convert about 22% of the power input to visible white light."