Could this be anything other than light bleaching?
- Thread starter TrentSteel
- Start date
TrentSteel
Active Member
Huh?
Light meters only a portion of the PAR spectrum, with a heavy emphasis on green. PAR runs from deep blue to red so the sensor in a light meter cannot pick up blue and red accurately. Cheap PAR meters can't read > 660 nm, either. The only way to get accurate readings is with a dedicated PAR meter. Apogee and LiCor are the big dogs but SPOT ON looks like a contender - I don't know if the SPOT ON uses a galium arsenide chip like the PhotoBio, et al.
Interestingly, the light I bought to replace the Kind was a Mars SP 3000 which is very similar looking to your light. One note on your light - if you compare the spectrum that they use against the spectrum for the Mars SP 3000, you'll see that your light is spikey in red and blue and lower in green and yellow. With a lower green level, that could make it a bit harder to spot issues with your plants. That's a guess, not something in which I have expertise, but it is one of the reasons why blurples fell out of favor - we had to wear special glasses to be able to see the plants when the blurples were running.
TrentSteel
Active Member
That's funny I was actually looking at the Mars Hydro Sp3000 before I purchased this light.
I 100% understand how blurples could make it harder to identify issues, colors were wildly distorted. I don't see how that can be an issue with the light I'm currently using though, as everything appears exactly as it should.
But I think I understand the science that has you leaning that way. In basic terms the human eye picks up the green spectrum more efficiently?
"Mars Hydro Sp3000" - it's a good light but I "retired" it after a couple of grows (so it's looking for a good home).
"as everything appears exactly as it should." - good. I was wondering if maybe you couldn't see how dark green your plants were. It was pretty strange with the blurples.
"In basic terms the human eye picks up the green spectrum more efficiently?" - yup and we don't see blue and red all that well compared to green. Bugbee said something in one of hid videos that hit home. I've been using gas for cooking since forever but when he said this, it made sense. He was talking about the red or far red part of the spectrum and he said that we can't see it very well and then "think of an electric stove - the burners look dark".
That's why we can't rely on our vision to gauge how bright an LED is to a plant - those are two very different sets of sensors.
TrentSteel
Active Member
Hmm, ya when I switched from the mars hydro to the aelius there was something about the light I just couldn't put my finger on, still clear white light but it was like my eyes were struggling to pick it up. Seemed off for the first few days.
I have read about the benefits of yellow/green spectrum on plant growth but they seem VERY minimal to the purpose of the red and blue spectrums for plant growth.
obijohn
Well-Known Member
There are no photos, just 3 boxes with what looks like a turned page corner. They don't open up when I click on them
TrentSteel
Active Member
Hmm, I'm not sure. Every pic I've posted on this forum appears that way to me as the page with a flipped corner, but they always seem to open fine. Maybe my crappy phone?
Agreed. Bugbee hems and haws a little and then says that those colors are needed to identify issues with the plants.
TrentSteel
Active Member
Its quite possible that the tint/shade is so minimally effected that I can barley tell, maybe my greens are slightly off.
I recall one of the benefits of the green spectrum was something along the lines of helping lowers reach up further into the light as the green has a higher penetration power, think it was referred to the "shade response", maybe I'm getting confused with something else does that sound familiar?
Per Bugbee, green photons penetrate more deeply into a leaf but essentially no photons penetrate the entire leaf. I've tested this with my Apogee and Shane at Micro (YouTube) did a short video on the topic, as well. In my testing, IIRC, the top of the leaf was getting 800µmols and the sensor was reading 50µmols± when held under the leaf.
[time passes]
Google "cannabis shade response" - good info there. I haven't seen these papers until now.
"Spectrum Colors and Cannabis: What are the Effects of Each Light Color?" is really interesting. It confirms that very little light gets through and, it confirms Bugbee in that it's the green photons that make it through.
TrentSteel
Active Member
Yea, I do believe I obtained that info. from one of bugbee youtube videos
VincenzioVonHook
Well-Known Member
@TrentSteel multiply your lux by 0.017 to get PAR. Migro goes over the formula and it's usually within a few percent of a par Meter.
I'm at 40k lux over 18 hours for 680umol/s, and a DLI of 44.6. my mates apogee reads 645umol/s.
Just realised you have a more blue/red spectrum. The lux Meter won't read the blues very well..
I'm at 40k lux over 18 hours for 680umol/s, and a DLI of 44.6. my mates apogee reads 645umol/s.
Just realised you have a more blue/red spectrum. The lux Meter won't read the blues very well..
Smart way to calibrate your lux meter!
Per the Excel table below, 0.017 is the factor for a CMH 3100k light. That doesn't mean that your light has the same spectrum as a CMH but that your light is putting out the same number of PAR photons. Per Bugbee, spectrum of a light influences plant shape; DLI drives photosynthesis.
HLG and Growcraft conversions are based on the data from the manufacturer's website, the others are from Apogee.
BTW, I did this table up just a few weeks ago and it's made me really rethink the whole Apogee vs lux meter vs Photone discussion. I've tested Photone, once when it was Korona and again just a few months ago. When I tested it using my iPhone XS Max, it was unusable on the blurple I owned at the time even though "red and blue" is a light source option. My subsequent test was with the same phone running against Growcraft X3 at 16" both the phone and the Apogee sensor were at center mass of the X3. For that test, Photone was consistently 16% high at 25, 50, 75, and 100% settings of the dimmer switch.
What concerns me. about Photone is how does someone with a device that can't be calibrated using a known good device get anywhere near correct values? Sure, the growlightmeter.com can publish their test results but what assurance does anyone have if they're phone isn't on "the list"?
What's the alternative? I looks to me that a lux meter will get you to in the ballpark really quickly. Light your plants with 55000 lumens and observe your plants. If there's no light avoidance, increase by a few percent and keep iterating until you see an issue. Or not. Even if you're actually at only 800 µmols, BFD — you're miles ahead of doing a grow at 500 or 600 or what have you.
Key point is that the rest of the grow environment needs to be optimized, too. With that increase in photosynthesis, you're going to see a lot more transpiration. Water uptake will increase and you might see some issues with ferts* if your EC is high.
I apologize for the long post. These ideas have been rattling around in my head for a while now and, I'll admit, I appreciate the ability to stand on the soapbox. I've collected bits and pieces of info I've picked up and I think it might help folks who don't have the time or interest to go foraging for this kind of info.
*I hate the term "nutes" - fertilizer is not food to a plant; light is food to a plant
Kassiopeija
Well-Known Member
Yes, fertilizer is food too, and it draws its power solar. Less anthropism, less confusion. It's different in any regard so that needs to be learned ground-up, "bananas"/anthers, "hairs"/...
ClaytonNewbilFontaine
Well-Known Member
I think this is what was going on with my plant a few weeks ago. I do end up letting my 3gal fabric pots dry out too much. I only like to water in the morning bc rh shoots up when the lights go out and it's worse after watering. Sometimes they could def be watered the day before but I'll wait until the next morning. I'm also using organic nutrients. I'll have to look for some info on this. The main issue I was experiencing, though it was pretty minor, were some yellowing and dropping leaves down near the bottom. Looking like N def. But then also slight tip burn on the rest. All of it was slight enough that it didn't effect much, but I did want to understand what she was telling me. If you've got any articles or links on this that would be awesome. I'm not sure what key words to even use to look this up.
Rurumo
Well-Known Member
As the media dries out, the EC rises. The moisture in the media keeps the EC more diluted, and as it dries out, those salts become more concentrated. This is why, when using coco, people often say to "never let it dry out." This is mostly true. But if you have a small pot of coco, with a seedling in it, and you're feeding a low starting EC, then even if the soil dries out, the EC won't be high enough to burn the plant. It's very common to get nutrient burn by letting a pot dry out too much.
VincenzioVonHook
Well-Known Member
Very informative post. I wouldn't trust the apps too much either. I use a uni-t bt Meter to read lux myself.Smart way to calibrate your lux meter!
Per the Excel table below, 0.017 is the factor for a CMH 3100k light. That doesn't mean that your light has the same spectrum as a CMH but that your light is putting out the same number of PAR photons. Per Bugbee, spectrum of a light influences plant shape; DLI drives photosynthesis.
HLG and Growcraft conversions are based on the data from the manufacturer's website, the others are from Apogee.
View attachment 5188578
BTW, I did this table up just a few weeks ago and it's made me really rethink the whole Apogee vs lux meter vs Photone discussion. I've tested Photone, once when it was Korona and again just a few months ago. When I tested it using my iPhone XS Max, it was unusable on the blurple I owned at the time even though "red and blue" is a light source option. My subsequent test was with the same phone running against Growcraft X3 at 16" both the phone and the Apogee sensor were at center mass of the X3. For that test, Photone was consistently 16% high at 25, 50, 75, and 100% settings of the dimmer switch.
What concerns me. about Photone is how does someone with a device that can't be calibrated using a known good device get anywhere near correct values? Sure, the growlightmeter.com can publish their test results but what assurance does anyone have if they're phone isn't on "the list"?
What's the alternative? I looks to me that a lux meter will get you to in the ballpark really quickly. Light your plants with 55000 lumens and observe your plants. If there's no light avoidance, increase by a few percent and keep iterating until you see an issue. Or not. Even if you're actually at only 800 µmols, BFD — you're miles ahead of doing a grow at 500 or 600 or what have you.
Key point is that the rest of the grow environment needs to be optimized, too. With that increase in photosynthesis, you're going to see a lot more transpiration. Water uptake will increase and you might see some issues with ferts* if your EC is high.
I apologize for the long post. These ideas have been rattling around in my head for a while now and, I'll admit, I appreciate the ability to stand on the soapbox. I've collected bits and pieces of info I've picked up and I think it might help folks who don't have the time or interest to go foraging for this kind of info.
*I hate the term "nutes" - fertilizer is not food to a plant; light is food to a plant
I tried the ppfd Meter apps with a 240w blurple and at 20" it was reading close to 1800umol/s on my phone, so not reliable at all at that spectrum. Without using the uni-t to calibrate lux on the app, it wouldn't even read over 650umol/s with my phone sensor, and even after calibration is was unreliable at differing proximity to the light.
To put it into perspective, ppfd Meter thinks my old 240w blurple with 120x3w epistar diodes is putting out 2.2x the PAR my 240w quantum board with 436xlm301 diodes does. If that doesn't raise an eyebrow....
That chart is a really nice reference by the way, and solves a lot of comparisons I had going in my head.
Last edited:
Yeh, I understand that. "Plants do not live by glucose alone,", or something like that.
I see growers focused on finding just the right combination of elixirs in hopes of increasing yield when adding more light will actually increase the yield (caveats apply, of course). And the cost of more light pales in comparison to the shekels that we shell out for a new potion, even at the 35 to 50¢ per KwH here in the People's Republic of California.
You were definitely getting wonky results there. Good on you that you switched.
Interesting that you mention that specific model of light meter. I'm sure that there are a lot of models being used but that's the only one that I recall seeing specified. I'm starting a grow in the next week or two and it would be interesting to use one in tandem with my Apogee to see how close they are.
"That chart is a really nice reference by the way, and solves a lot of comparisons I had going in my head."
Glad that you found it useful and I hope others do, as well. It would be nice is cannabis sites allowed growers to post things like Excel documents but no such luck.
Similar threads
