Delps8
Well-Known Member
Strictly speaking, you don't have to even do that.
You can use lux to set light levels for your grow. Below is a simple table will give some idea of what light levels to use. I think in PPFD which is expressed in µmols/second/square meter ("µmols"). PPFD indicates how many photons are hitting one square meter of the canopy every second. Read that description again and then forget about it.
The table above is the way that I grow cannabis. Those light levels work for my environment and many growers and many sources on the internet will disagree with them because "those light levels are too high". If your grow environment is optimized, cannabis will benefit from a staggering amount of light.
A key point is that my grow has pretty good conditions - temperatures are usually close to optimal, VPD rarely leaves the optimal level, I run a large dehumidifier in the garage, the humidifier in the tent is electronically controlled, water temperature is constant, my RO water is consistently 0 PPM, nutes are measured to 0.1±gm, I use a calibrated Apogee MQ-500, etc., etc.
Scroll back to message #14 in this thread which is my posting with the images and the table.
You want to take readings in lux.
No. And it does not matter. And it is as complex as you want to make it.
Details
If you refer to message #14 in this thread, the first graphic shows that the human eye is very sensitive to green light and less so toward the blue and red parts of the spectrum. Lux meters report the amount of light in this range.
The spectrum that we use to describe where plants are most sensitive is referred to as PAR. It's a different set of wavelengths and plants are more sensitive to some parts of PAR than others.
You can covert lux to PAR - that's what message 14 illustrates.
"compromised" - that's a "How many angels can fit on the head of a pin?" discussion. What does "compromised" mean?
We can prove that the light output from one SF2000 is different from the next one coming off the line. It's a tiny difference — is that "compromised"? Not to me.
Your light will be putting out fewer photons and a different mix of photons after it's been used for a week, a month, a year. It's measurable and reproducible. Is that "compromised"? No.
Consider - "Measurable but insignficant." That covers a lot of things in life.
The other day, I took 41 samples when I took light readings. I could not possibly reproduce those values because light levels are measurably different if the sensor moves less than 1" from the light source.
The goal of a light meter for most cannabis grows - and this is why I recommend a light meter even though I have a PAR meter - is to get you close and then allow you to "adjust fire".
Assuming the other parts of the grow environment are…up to par, those light values will result in a bountiful crop.