Min & Max Lux at canopy

[kushedy]

Can anyone tell me the minimum & maximum lux at canopy when flowering with COB LED’s?

I know that ppfd readings are more accurate/appropriate but I don’t have a par meter & I’m not in a position to get one anytime soon. I do however have a lux meter app on my phone. Probably not the most accurate in the world but a starting point at least.

There are a number of posts on various forums/threads with differing views on this. I’ve seen a thread stating that anything over 58,000 lux will cause chlorophyll degradation. I’ve seen another saying the max lux is 75,000 & another for 90,000.

I would be grateful if anyone can clarify?

 

[Chip Green]

I'm guessing the discrepancies are due to differences in measuring devices.
For instance, I have a "Dr. Meter" brand, LUX meter, $25.... With my Bridgelux EB series panels, I can get readings over 50,000 at about, say 6-8".... Before I had that meter, I had the panel only 4-5" away from the canopy, and had one bush turn Lily white.....Since then, keeping sub 50K readings with MY METER, I haven't had any white-outs.....
Now, I've never compared the "Dr. Meter" to a LUX App, maybe I should just to see....

Like you mentioned, LUX isn't the most beneficial way to test light levels, but in my case, whether or not my meter is "accurate" is meaningless, its a way to get a general, RELATIVE, light level...

 

[kushedy]

Hey @Chip Green thanks for the response. So, around the 50,000 figure is the safe max for you. Is the 50,000 lux you settled on solely based on the experience you had with your plant turning white or to do with something else?

 

[BuddyColas]

I'm guessing the discrepancies are due to differences in measuring devices.
For instance, I have a "Dr. Meter" brand, LUX meter, $25.... With my Bridgelux EB series panels, I can get readings over 50,000 at about, say 6-8".... Before I had that meter, I had the panel only 4-5" away from the canopy, and had one bush turn Lily white.....Since then, keeping sub 50K readings with MY METER, I haven't had any white-outs.....
Now, I've never compared the "Dr. Meter" to a LUX App, maybe I should just to see....

Like you mentioned, LUX isn't the most beneficial way to test light levels, but in my case, whether or not my meter is "accurate" is meaningless, its a way to get a general, RELATIVE, light level...

I second that. I too run the EB strips and have found 50K lux to the canopy very doable and very productive. From various conversions, that is about 750ish umols for "warm" cobs/mid-power leds. Despite all you read, that is very productive.

 

[CobKits]

700-900 umol is great. only expert growers with really dialed setups make use of 1000-1500 ppfd and your yield per watt goes down at the higher intensities anyway

 

[kushedy]

Thanks for the responses. @CobKits at the risk of sounding thick, what is 700-900 umol in Lux roughly? Is their a conversion calculation of some sort?

 

[CobKits]

depends on the spectrum of the light, its a pretty wide range as lux is a green-centric measurement and leds we use can be all over the map in the green department depending on kelvin temp, if its 80 or 90 cri, if its augmented with reds and blues, etc

 

[kushedy]

@CobKits 3500k

 

[Chip Green]

Hey @Chip Green thanks for the response. So, around the 50,000 figure is the safe max for you. Is the 50,000 lux you settled on solely based on the experience you had with your plant turning white or to do with something else?

Its was both actually..... first it was at the recommendation of Buddy Colas up there, since I was building my lights with the same parts he is experienced with. My first run, I didn't know the LUX, didn't have the meter yet, went white out pretty fast. After the meter came, I realized I was north of 60,000. The 2" increase in height between 60K and 45K ish, saved the much needed green....

Then, on a subsequent foolish experiment, I got greedy and tried 60,000 again, and AGAIN proved his recommendation to be accurate....

 

[kushedy]

Thanks @Chip Green. Sounds like I may have had my lights a tad to close then. Live & learn.......

 

[1212ham]

Recent threads...
https://www.rollitup.org/t/help-with-par.957065/#post-14015128
https://www.rollitup.org/t/cob-users-what-is-your-lux-at-canopy.932040/page-2

 

[GBAUTO]

I agree with Chip, lux measurements are only useful for keeping the same relative intensity. It's an easy way to keep your lighting at the same intensity-once you have figured that out...

 

[kushedy]

@1212ham thanks for the links. I've read them already. I did a bit of looking around online off the back of one of those threads & that's when I started coming across contradicting max figures so I started up this thread to try & get some clarity.

@GBAUTO cheers I understand it’s not the best tool for the job but it’s a starting point.


I think I have the drift. Around the 50,000 figure is the sweet spot & with a well dialled in grow & experienced grower anything up to 100,000 Lux

 

[1212ham]

I second that. I too run the EB strips and have found 50K lux to the canopy very doable and very productive. From various conversions, that is about 750ish umols for "warm" cobs/mid-power leds. Despite all you read, that is very productive.

Veg or flower?

 

[BuddyColas]

Veg or flower?

I shoot for about 50000 LUX in flower at the top of the canopy. I bult my fixture using EB strips about 3.5" apart and run the fixture about 4" from the canopy. So 7 strips wide for a 2x4 foot tent. Very even coverage.

Note: I do have flat-canopy OCD...your results may vary!

 

[GBAUTO]

@1212ham thanks for the links. I've read them already. I did a bit of looking around online off the back of one of those threads & that's when I started coming across contradicting max figures so I started up this thread to try & get some clarity.

@GBAUTO cheers I understand it’s not the best tool for the job but it’s a starting point.


I think I have the drift. Around the 50,000 figure is the sweet spot & with a well dialled in grow & experienced grower anything up to 100,000 Lux

What I was trying to illustrate is that using a lux meter only allows you to duplicate YOUR conditions. Because of the way it measures light, the meter readings can't give you an accurate comparison of two different lights. It will allow you to repeat the same light intensity using the same light source. Just doesn't allow you to create identical conditions unless using the same meter and same light.

 

[kushedy]

I know that using a free lux meter app on an android phone is far from ideal & different spectrums & give different results (correct me if I’m wrong).

Hypothetically though say for instance I was trying to get the same intensity as a friend running the same make & spectrum of cob & we both used my phone to measure lux around canopy level would this not at least allow us to get in the same ball park by adjusting hanging height or dimming according to the readings?

Please don’t get me wrong here I am not trying to be argumentative, I’m just trying to understand, are you saying that using lux reading is completely pointless? Again, correct me if I am wrong here but I thought lux meters measured intensity & although not the most suitable would allow someone to work out a rough hanging height?

 

[BuddyColas]

I know that using a free lux meter app on an android phone is far from ideal & different spectrums & give different results (correct me if I’m wrong).

Hypothetically though say for instance I was trying to get the same intensity as a friend running the same make & spectrum of cob & we both used my phone to measure lux around canopy level would this not at least allow us to get in the same ball park by adjusting hanging height or dimming according to the readings?

Please don’t get me wrong here I am not trying to be argumentative, I’m just trying to understand, are you saying that using lux reading is completely pointless? Again, correct me if I am wrong here but I thought lux meters measured intensity & although not the most suitable would allow someone to work out a rough hanging height?

You don't have to worry about being argumentative, someone will get their panties in a wad and argue with you just because you posted! Just ignore them.

My opinion...even at the very least a lux meter is good for adjusting cob bar spacing or light heights to get the most even readings at the canopy. From my experience, generally speaking, the spacing between your cobs or strips is a good place to start with hanging height. So if your cobs are 8" apart, then start with your lights 8" above your canopy.

AND, you can take the PPF for your fixture divided by the number of square feet you are covering, then multiply that by 10.76 and you get the PPFD (theoretical max) your plants will get. I try to "build" for about 800 ppfd.

And your job is to hang/space your lights and train your canopy so your girls get hit by most of those photons!

 

[kushedy]

Cheers @BuddyColas , the hanging height was my main concern & i'm seeing improvements in my girls health after adjusting my fixtures height based on lux so all good.