What ppfd values and height should I hang my leds at?

[Delps8]

I've watched so many videos by Dr Bugbee and interviews with Dr Bugbee. He is the reason why I splurged on a
MQ-500: FULL-SPECTRUM QUANTUM METER. I still have sooooo much more to learn.

Yup, you drank the Koolaid! How do you use it to improve your crop?

 

[Delps8]

Here's a really strong argument for "crank it up to 11".

 

[Delps8]

I don't have a ppfd meter and had a lot of trouble getting the height perfectly every time, until I realized the plant can tell you. So this system works for me:

1. Put the light at a height that won't hurt your plants.
2. Every day, check to see if your plants are praying (see below). If they're not, lower the light again. If they are, you should raise the light about four clicks if you need more coverage in the tent. But leave it alone if it's only one plant and it's getting good coverage.

Cannabis plants pray when they're getting an abundance of light. My favorite level is the one that causes the plant's leaves to cant upwards at a 15° angle. It's my thinking that the plant angles its leaves to reduce the amount of light.

If the plant is praying, it's getting more light than it needs (so it's thankful and prays). You can use that information to provide the best light possible in the tent. The higher the light is, the more coverage it gives. So if I'm in a tent with several plants and need coverage, I will raise the light just until the plants stop praying. But if I have one plant under the light, I'm going to drop the light down until I get that 15% upward cant.

Anyway, that's what I think I have learned. Do with it what thou wilt.

That's really ingenious!

 

[WildBill]

Here's what I and a few other members have. It works great!

Amazon product

 

[N/A-Greengo]

Here's what I and a few other members have. It works great!

Amazon product

I second the PhotoBio, it's an accurate meter. Eliminates the guess work, and is very affordable.

 

[Big Sul]

I second the PhotoBio, it's an accurate meter. Eliminates the guess work, and is very affordable.

 

[RiseAboveTheFlame]

I've done a fair amount of poking around in this and decided to go with a PAR meter. Not cheap but it is accurate.

I tested Photone about a year ago (it was called Korona back then) and my results were not what I was expecting but, based on emails between myself and the programmer), my sense is that Photone will get you in the ballpark.

Some growers use a LUX meter. That's fine for taking pictures but, seeing that a lux meter/light meter measures a different spectrum, a lux meter is going to be very inaccurate. Some manufacturers publish data that you can use to convert the reading from a lux meter to a reading of PAR. If you've got a light for which that data is available, that could be a cost effective approach.

Next step is to go to a PAR meter. I decided against the "budget priced" PAR meters on Amazon and, based on comments I've read in the intervening year, I'm glad that I did. I ended up getting an Apogee and have been able to take advantage of most of its features but, looking at the market today, the PAR meter that Shane is selling on his site (migrolight.com) seems to be a good buy. You get a lot of features for the extra $$ (the Apogee is about $600 vs <$300 for Shane's meter) but they may not be worth the extra funds.

Thanks for the responses. And sorry to hijack your thread OP.

I think I'll stick it out for now without a par meter. Maybe I'll calibrate the app when it comes to it. Probably will end up maxing out the light, and put in a CO2 bag if necessary. But I have a measely 250watt maxisun... soooo

 

[GinFizzLuv]

Here's what I and a few other members have. It works great!

Amazon product

I just bought this PAR meter. How many hours are your lights one What DLI are you aiming for? How quick do you ramp up PPFD when the plant starts to stretch

 

[Need4Weed]

I recently downloaded this app on my iphone & I used it to dial-in an additional light to increase heat during my current grow!
Here's a screen shot.

 

[WildBill]

I just bought this PAR meter. How many hours are your lights one What DLI are you aiming for? How quick do you ramp up PPFD when the plant starts to stretch

LOL! Lots of tech questions.........................with 'Depends' is the only 100% accurate answer.
Plenty of articles and vids on DLI to give you accepted ranges.

Here's a few things to have in mind that most articles and vids don't go into.

Before I had to quit the current grow, Both tents were on 24/0 for the heat without aux heat to the lung room.
At 3 weeks, I had the lights at 600 umol/s/m2 and 24 hrs.
That's 51.84for DLI. That's fairly aggressive, but nowhere near extreme at that point, but they were in great condition. 65 is the accepted max DLI for cannabis to perform at it's max.
Most had already begun to flower. This week I would have stepped up the lights. I'd up it 100 umol/s/m2 and see how they react after a couple days. If they are fine, step it up again and watch. or just let them 'grow into' the lights for the increased light. Ya have to keep an eye on them closely for leaf changes....not only for burn, but any nute def comes up from driving them harder. You'd be too close to having a problem if that bumped it over the edge, but you get the idea. This depends also on your VPD. If you're driving them pretty hard with a higher VPD, it's not a bad idea to lower the VPD for a few days to limit the stress..

If I were still my grow, at this point I would probally stagger my two tent's off time by 2hours and set them on 22/2 to give them a rest period and reasonably keep the lung room warm enough. I'm 100% organic, so keeping up temps keeps my tiny helpers more happy.
I feel if you grow salt base, the above conditions are more critical to get right for a problem-free and quality prime bud production.