420 Magazine Background

Are we using too much light?


420 Sponsor
we know that Sara, but not everyone can buy a PAR meter, that just converts LUX anyways, its a big LED community scam. I have done tests to confirm this also, so its not just me talking crap, PAR is great for the producers of the light for a Selling Point, but in little home grows, Lux meters work just fine, staying with the notion that LED growers burn their plants because they give them to much light, and thats a fact.

Intensity is intensity regardless of light, and Both the $153 PAR meter and the $30 Lux meter is just the same, The Lux degrades with distance, as does the PAR meter, at the same rate.
Yes, at that point your right. At the old days when we don't have par meters, we also only test with lumen, but usually good chips are with higher lumens and par as well. So it can be used for reference. :slide:


Active Member
I Have a cheapo Dr Meter, Lux meter that I use, The guide below is what I have been following, It is from GWE

Quick Guide – Lux Levels for Optimal Cannabis Growth
Life StageMaximumGoodMinimum
Vegetative70,000 lux40,000 lux15,000 lux
Flowering85,000 lux60,000 lux35,000 lux
< 15,000 lux – sparse or “stretchy” growth – plant isn’t getting enough light
15,000 – 50,000 lux – a good amount of light for healthy vegetative growth
45,000 – 70,000 lux – the optimal amount of light for cannabis plants in the flowering (budding) stage. If grow lights produce a lot of UV light (such as LEC), stay on the lower side of this range
70,000 – 85,000 lux – a lot of light, some strains thrive at this light level, but some plants (especially auto-flowering and Indica strains) lose their top leaves early under this light intensity. At these levels, lights need to be kept further away for healthy growth
> 85,000 lux – at this light intensity, you’ve hit the plant’s “saturation point” which means your plant can’t use all the light (most strains will experience light bleaching or other major signs of stress at this level!)

Jay T Trichomes

Well-Known Member
This is only my 2nd grow, but everything I’ve read for the last few years says ppdf is the best reading to take for plants? Am I wrong for thinking this. ? Here is a pic of the meter I use to measure Ppdf. This pic is from weeks ago and it shows ppdf around 900. That was my sweet spot for early on in flower. They are weeks past that now and I have my lights close enough to get about 1050 ppdf. And they seem great. I’ve also heard that anything above 1000pdf is pretty much useless unless you have a sealed room and c02 levels high? What’s everyone’s thoughts on that.? I have never even measured lumens in any of my tents. Should I be???


Member of the Month: May 2009, Oct 2010, Sept 2017
This pic is from weeks ago and it shows ppdf around 900. That was my sweet spot for early on in flower. They are weeks past that now and I have my lights close enough to get about 1050 ppdf.
:thumb:. It's PPFD, by the way, not PPDF. We understand what you mean, but if you ever feel the need to do a web-search for information, getting the letters' order correct might save you some time.

Here is a pic of the meter I use
Nice meter, Apogee makes good ones. Be sure to check the manufacturer's website to see if a firmware update is available, as they do occasionally release updated code. For example, I was reading some related information at a reefer (salt-water coral enthusiast) website one day and saw where someone had tested several popular PAR meters against a very expensive meter that was known to be accurate and calibrated, something that some of the companies use for testing/R&D I think. Anyway, the person discovered an issue with a couple of meters, one of which was an Apogee. He contacted the manufacturers with his findings and was contacted back by someone at Apogee a week or so later; the person stated that they had just updated the firmware for that particular model and invited him to test it (problem was fixed). I consider that a good indicator that it's a decent company... Far better than when many people report an issue to a company and they only end up quietly releasing a fix a year later (if at all), IMHO.

Yeah, you're on the cusp of rapidly diminishing returns, I'd guess. Adding more light-energy to what you're already supplying them probably wouldn't give you much in the way of benefits unless you were also adding supplemental CO₂ (and providing the warmer temperature to facilitate things).

Good job! Do you get a lot of requests to borrow your meter? Can I be your neighbor, lol?


Well-Known Member

20,000 lux, about 305 PAR 12/12 from seed, day 74, Over water stunted at beginning, was solo cup experiment to see if i could water everyday, then decided to transplant and it slowed it down, so about 2.5 weeks behind, same genetics as last post pic above.


Well-Known Member

less then 15,000 lux, about 230 PAR, Cherry Wine CBD- 24 days from seed, 12/12 from seed, but 3 days ago, topped again and 18/6 now. Might scrog, might throw in the bin,lol.. undecided, its a 10 week flower strain, not sure i want to take up my entire area for 10+3 weeks more, when i can put in my FireOG cross and be done start to finish in 65 days, hummmmm, but the cherry wine grow fast as heck. She sexed in like 16 days from seed, my FireOG cross sexes in 21-24 days from seed. tuff decision.


Well-Known Member
This guy says 800 foot candles is enough to grow decent cannabis with. Not great. But decent.

I'm measuring 1500 foot candles at the top of my smallest plant. And over 4,300 foot candles at the top of my tallest plant 1' from the lights. I'm only using 140 watts with my 4 cob system. According to this I have plenty of light and don't have to turn it up higher through the whole grow. LUX is roughly the foot candle reading multiplied by 10.

Last edited:
Top Bottom