FLIR leaf temperatures & VPD

Wondering people’s thoughts on what information a FLIR image can give in relation to humidity, light, EC or temperature adjustments.
This photo @ ambient 28.8, 65% humidity, led600w ec.7 dwc
After this photo I raised the light a little and turned off a couple of fans, slowed extractor to let humidity come up. Was this correct do people think?
Thanks, the vpd concept took me some reading.

...at what altitude are the plants referenced to sea level?....above 500 m ...maybe you must correct the calcs in function of altitude of your cultivar...
















DLI Chart...thanks to Ledtonic...similar to VPD Charts...but for DLI...




e function desactived...le gusto al autor del hilo...este no lo borrare...enjoy the info...

Paz y Amor....en 2021 aun mucho mas...

Saludos desde Tenerife - Islas Canarias

Anything red or white is exceeding recommended vpd.

As a reference, I'd put a piece of electrical tape (black or blue) on a small cut up piece of aluminum can in the canopy. That should give you an emissivity reference of the air temperature. I haven't tried it yet, since I'm still in the seedling stage, but I'm curious to see if my theory plays out and if you can accurately determine the leaf vs. air temperature with a FLIR. Eliminate error with a single measuring device and two targets?

I also had a shower thought of using an IR sensor on an arm, with an air piston to rotate the sensor - position 1 records a leaf temperature, position 2 records the aluminum/electric tape temperature. Or, if we really wanted to get fancy, have a roving robot with an IR camera and optical pattern recognition go up and down the aisle measuring leaves and targets while recording temperature differential!

Marking this thread for when I'm smarter.

Chopshop697 said:

I also had a shower thought of using an IR sensor on an arm, with an air piston to rotate the sensor - position 1 records a leaf temperature, position 2 records the aluminum/electric tape temperature. Or, if we really wanted to get fancy, have a roving robot with an IR camera and optical pattern recognition go up and down the aisle measuring leaves and targets while recording temperature differential!

Click to expand...

Great idea, I’ll try it. I’ll also try pics of a few different environments. Bottom leaves freezing, hot tops... what does that mean? In dwc it is low nutrient?
the difference in leaf surface indicates low vpd in lower canopy leaves, high at top. More food?

Roy O'Bannon said:

Marking this thread for when I'm smarter.

Click to expand...

Salmonetin compiled a great selection of reference. Thanks again.

Not sure how the FLIR calculates the max and min, but it looks like you're within about 2 deg C from low to high. Certainly not freezing! My understanding is that the temperature differential of a sweating leaf vs. true ambient at the same height is the input to a VPD determination.

Chopshop697 said:

Not sure how the FLIR calculates the max and min, but it looks like you're within about 2 deg C from low to high. Certainly not freezing! My understanding is that the temperature differential of a sweating leaf vs. true ambient at the same height is the input to a VPD determination.

Click to expand...

Great thanks, theres a bit of an ambient temperature gradient too. And humidity. 28.8 measured top canopy level.
FLIR calcs from manual circles in the scene.
They’re not quite growing right. Thin, salted tips.

Bratt said:

Wondering people’s thoughts on what information a FLIR image can give in relation to humidity, light, EC or temperature adjustments.
This photo @ ambient 28.8, 65% humidity, led600w ec.7 dwc
After this photo I raised the light a little and turned off a couple of fans, slowed extractor to let humidity come up. Was this correct do people think?
Thanks, the vpd concept took me some reading.View attachment 4863871

Click to expand...

I think this thread points out some of the problems with using vpd as a tool for finding a "perfect" environment; it's better thought of as a "dial-in" factor for which direction to take your environment, not an exact goal as this may differ from one grow to another and especially to one set of measuring equipment. We tried a few IR-thermometers that varied around 2 degrees C and we're stumped on what values to use.

It's well worth remembering that vpd is only one of the factors that affect transpiration/stomata opening:
- Blue/violet/uv light all have an effect on stomata opening it. This means if you build a wide blue channel into your grow light you can compensate if you cannot get your transpiration right.
- CO2 : more ambient co2 tends to close the stomata decreasing transpiration.
- atmospheric pressure: I'd have to double check to be sure but iirc the vpd equation refers to atmospheric pressure somewhere which I assume most the tables bouncing around the net would set as standard sea level. But growing in altitudes, storms or with a negative or positive pressure would affect the air pressure which throws another wrench in the numbers. This is why I suggest it's pointless to try to find answers to what exact temp/the/vpd you should go for. I think for the fine-tuning we are just stuck with standard practice: make changes and see how the plants respond. What will help you in this case (more than a flir) is a unit which measures, displays and log your vpd. This way you will always have that reference point available and not hiding behind tables and calculations.
I know trolmaster and pulse have some, but they're expensive, I think there's also instructions on ledgardener on how to do it with google home assistant.

Rocket Soul said:

I think this thread points out some of the problems with using vpd as a tool for finding a "perfect" environment; it's better thought of as a "dial-in" factor for which direction to take your environment, not an exact goal as this may differ from one grow to another and especially to one set of measuring equipment. We tried a few IR-thermometers that varied around 2 degrees C and we're stumped on what values to use.

It's well worth remembering that vpd is only one of the factors that affect transpiration/stomata opening:
- Blue/violet/uv light all have an effect on stomata opening it. This means if you build a wide blue channel into your grow light you can compensate if you cannot get your transpiration right.
- CO2 : more ambient co2 tends to close the stomata decreasing transpiration.
- atmospheric pressure: I'd have to double check to be sure but iirc the vpd equation refers to atmospheric pressure somewhere which I assume most the tables bouncing around the net would set as standard sea level. But growing in altitudes, storms or with a negative or positive pressure would affect the air pressure which throws another wrench in the numbers. This is why I suggest it's pointless to try to find answers to what exact temp/the/vpd you should go for. I think for the fine-tuning we are just stuck with standard practice: make changes and see how the plants respond. What will help you in this case (more than a flir) is a unit which measures, displays and log your vpd. This way you will always have that reference point available and not hiding behind tables and calculations.
I know trolmaster and pulse have some, but they're expensive, I think there's also instructions on ledgardener on how to do it with google home assistant.

Click to expand...

I guess the vpd information and calculating it told me how I could back the “pressure” off the plants while I figured out a better E.C. Or what the problem was. The FLIR showed up hot grow points, very close to ambient. I’m not sure how vpd relates to plant parts, but it’s calculated higher when the ambient/LST differential is small.
vpd also told me I was exactly in the zone, the plants should be doing better. CO2 @1250.

So. Doubled the EC. Ambient 28. No sub 2 degree difference. They look better. Still raising EC, and VPD. Light now max. Note scrog net inability to cool itself.

Bratt said:

I guess the vpd information and calculating it told me how I could back the “pressure” off the plants while I figured out a better E.C. Or what the problem was. The FLIR showed up hot grow points, very close to ambient. I’m not sure how vpd relates to plant parts, but it’s calculated higher when the ambient/LST differential is small.
vpd also told me I was exactly in the zone, the plants should be doing better. CO2 @1250.

So. Doubled the EC. Ambient 28. No sub 2 degree difference. They look better. Still raising EC, and VPD. Light now max. Note scrog net inability to cool itself. View attachment 4868859

Click to expand...

Remember: if you raise vpd and ec at the same time your plants will transpire and drink more and on top of that the feed is stronger. Better change one thing at a time

Chopshop697 said:

As a reference, I'd put a piece of electrical tape (black or blue) on a small cut up piece of aluminum can in the canopy. That should give you an emissivity reference of the air temperature. I haven't tried it yet, since I'm still in the seedling stage, but I'm curious to see if my theory plays out and if you can accurately determine the leaf vs. air temperature with a FLIR. Eliminate error with a single measuring device and two targets?

Click to expand...

So My thinking is. Under LED, where IR doesn’t add 2deg, either ;
Above 26 LST is bad, or;
Ambient/LST differential below 2 is bad.
Because, photosynthesis is compromised at the hot location, not because of the light. In my case, low EC, pumped water through plant, drinking loads, but tip nutrient was too low to keep up with the demand.
Maybe sort of feedback loop too? Increased LST at tips = increased VPD = even higher demand?... Nek minute tips are cooked, or throwing boy bits.
Whatever the case, these tips have cooled with an EC correction. It appears at this stage... so far so far..

Rocket Soul said:

We tried a few IR-thermometers that varied around 2 degrees C and we're stumped on what values to use.

It's well worth remembering that vpd is only one of the factors affect transpiration/stomata opening:


- the vpd equation refers to atmospheric pressure

what
in this case (more than a flir) is a unit which measures, displays and log your vpd.

Click to expand...

FLIR might provide insight into the heat distribution? more visual than an IR gun.

The key point. VPD is only one factor. But try and get it in the zone I think It’s been helpful to me, combines transpiration energy (cooling power, evaporation + photosynthesis ? ), humidity & temperature.

Haven’t plugged in pressure, anyone know how much influence that has? the influence humidity and temp play in the calculation is intuitive and reasonable resolution to make small adjustment.

I’d love a vpd controller..

Out of interest, an impressive demonstration of cottons ability to cool itself.