Is my massive leaf offset normal??

beezyacreapiary · Sep 2, 2025

So I’m borrowing a (firefighter) friends THOR thermal camera to map out my canopy and set my leaf offset temp. I’m running a 4x4 with mostly ac infinity gear. The tent is super efficient and the girls seem to love it, but this $500 thermal camera is telling me that my leaves are -10 to my ambient (controller reading). It feels kind of crazy jacking my tents ambient temperature up to 92 degreees, but the offset adjustment on the controller works the vpd out to my target (.9-1). Idk; it just feels weird, and I can’t find anywhere online where someone’s leaf offset was bigger than -3… should
I trust the gun? Or just set my offset to -2 and forget it? Just looking for outside opinions from my own, a little tired of going back and forth with myself and asking online.
Also, just a note: my acinfinity ir gun and my cheap kitchen gun all read relatively close to the -10 number..

Thanks in advance yall

Gmix · Sep 3, 2025

I dunno what you mean by offset
I do know I’ve never heard of 92f. That’s a mad temp unless there’s co2 involved

Gmix · Sep 3, 2025

I kinda get what your trying to say I don’t think you should be using a cam to tell you what temp to run

I’m not the guy to help you with that as I don’t bother with that sort of stuff I just set my tent to as close as 74f-80f & that’s works

I seriously don’t think you should be running higher than 80f

KG1 · Sep 3, 2025

Do you have dry and wet bulb readings, and accurate soil moisture reading, wind speed in m/s to plot a more accurate vpd. There are more data points one would like to know as well.

If not don't take too much notice of leaf temperature and vpd, it's quite a complicated thing to measure and achieve anything meaningful from.

Leaf temperature offset can signal a whole host of things from simple low moisture or root uptake to serious virus and disease.

If your measuring leaf offset in expecting you to tell me not the other way round.

Vpd is pretty useless at our levels, not how the commercial indoor tomatoes or whatever donut.

Florida_Mike · Sep 3, 2025

beezyacreapiary said:
So I’m borrowing a (firefighter) friends THOR thermal camera to map out my canopy and set my leaf offset temp. I’m running a 4x4 with mostly ac infinity gear. The tent is super efficient and the girls seem to love it, but this $500 thermal camera is telling me that my leaves are -10 to my ambient (controller reading). It feels kind of crazy jacking my tents ambient temperature up to 92 degreees, but the offset adjustment on the controller works the vpd out to my target (.9-1). Idk; it just feels weird, and I can’t find anywhere online where someone’s leaf offset was bigger than -3… should
I trust the gun? Or just set my offset to -2 and forget it? Just looking for outside opinions from my own, a little tired of going back and forth with myself and asking online.
Also, just a note: my acinfinity ir gun and my cheap kitchen gun all read relatively close to the -10 number..

Thanks in advance yall

Welcome to the farm!

Tell us more about your setup - medium, water source,
type of lights, power settings, nutrients, etc. As well as
some good pictures, both whole plant as well as close-
ups. This will help us to better advise you

I grow in rockwool with constant recirculating feed.
With this setup I can get away with temps in the 90's,
bc it keeps the roots cool and oxygenated and allows
the plant to drink & transpire all it wants.

I don't pay any attention to vpd or any of that crap,
but it can be helpful to noobs, like training wheels.
Your best bet will be to aim for 75-80f and not waste
much time worrying about it.

JIMKSI64 · Sep 3, 2025

Unless you have your roots in an ice bath with bigly transperation you do not have a 10 degree offset.
I used and have a flir for tracing hot circuits for parasite loads. These cameras do a great job of finding differences of temp but a poor job of temperature measurement. The +- of my unit is over 15 degrees depending on type of heat generated. Actual radiant heat from flames is very poor but say a hot pipe measurement would be more accurate but still nothing to set a data point on.
I do not even think a leaf off set is possible outside a lab. Your air sensor has a standard deviation and your non contact has a deviation. You can not zero them and as soon as you open the tent airflow changes.
No useful data sets.

JIMKSI64 · Sep 3, 2025

FloridaMike said:
I don't pay any attention to vpd or any of that crap,
but it can be helpful to noobs, like training wheels.
Your best bet will be to aim for 75-80f and not waste
much time worrying about it.

Just because you do not track vapor pressure deficit does not mean you do not modify your VDP in your tent.
Do you maintain your temp and humidity within a certain range? Do you reduce humidity during flower?
The idea that a simple principle of technology has only training wheel applications is insulting to growers who use technology to increase yields and potency.
I am pretty sure I have seen a light reading with a DLI data set from your tent but it also might have been other Mike. I have seen growers remark on this bit of useless tech also.
To grow pot you need a seed.
Everything else is extra.

Gmix · Sep 3, 2025

JIMKSI64 said:
To grow pot you need a seed.
Everything else is extra.

Tbh I hardly take notice of my temps / humidity anymore I might check on very hot/cold days but that’s about it

Guess after time you know just by opening the door & looking in if alls going good

I could never chase numbers it grows despite what the grower does to it

KG1 · Sep 3, 2025

JIMKSI64 said:
Just because you do not track vapor pressure deficit does not mean you do not modify your VDP in your tent.
Do you maintain your temp and humidity within a certain range? Do you reduce humidity during flower?
The idea that a simple principle of technology has only training wheel applications is insulting to growers who use technology to increase yields and potency.
I am pretty sure I have seen a light reading with a DLI data set from your tent but it also might have been other Mike. I have seen growers remark on this bit of useless tech also.
To grow pot you need a seed.
Everything else is extra.

The simplified version would have me see at least noticeable changes if I grew one crop at 35% humidity and another at %70. Even changes as the environment shifted humidity...

I've never reproduced these results in fact I have to really saturate the air for leaves to give any noticeable visible change such as leaf angle.

A more in-depth and frank discussion needs to happen at some point, unless excessively past 30-70% for long periods I've seen no influence or reason to concern myself with humidity.

Although I'm sure it plays a big part and I'm within tolerance for the leaf stomata and overall growth I've come to realise it has some of the least effects on growing indoors.

Also since when did someone have a problem and it got solved by a 20% humidity change? Just don't see that or plants making a miraculous U-turn because of.

Until now just seems like the least important thing on my list, only thing that ever made a difference was altering light temperature and air speed, never had a humidity problem.

I do chuckle at those that run humidifiers in tents or dome seedlings, a lot said by those who do the opposite and produce stellar results despite the wrong humidity.

More data needed, more years to pass for companies to catch up, I mean most are just starting to understand pH and basic things give them time. That's where the debate is for me.

JIMKSI64 · Sep 3, 2025

I have made some vdp related discoveries in my own tents. One of the most critical areas of a grow tent is to mimic the slow changes of vdp that we get from the largest lung room , the planet.
When I was in my 31x31 and with both the cloudforge and thermoforge keeping a steady vdp was easy. This 4x4 has been more of a challenge and it took about 4 weeks to get it dialed. The most obvious thing wrong was the leaf presentation. Little droopy little krinkly in the front but ok in the rear. At that point my vdp variance ( high and low over an hour ) was .18
My humidity had a bounce. Vdp tracking 1.1 to 1.28 was causing a cycle to develop on the transperation of the plant. The interior pressure of the water in the plant was not steady enough to lift the leafs and the growth was suffering.
I had to modify airflow and fix some leak paths for the incoming airflow from the lung room. This resulted in an average .04 vdp wave giving me a very stable environment in the tent.
It was not lights.
It was not nutes.
It was airflow and without the ability to graph my environment I would still be looking for the reason.

Florida_Mike · Sep 3, 2025

JIMKSI64 said:
Just because you do not track vapor pressure deficit does not mean you do not modify your VDP in your tent.
Do you maintain your temp and humidity within a certain range? Do you reduce humidity during flower?
The idea that a simple principle of technology has only training wheel applications is insulting to growers who use technology to increase yields and potency.
I am pretty sure I have seen a light reading with a DLI data set from your tent but it also might have been other Mike. I have seen growers remark on this bit of useless tech also.
To grow pot you need a seed.
Everything else is extra.

You've seen vpd readings on my infinity controllers, however;
I pay no attention to it. I don't have a light meter. The other
mike tracks all that, I have no need to.

Why you feel insulted is beyond me. Training wheels are only
needed until you learn how to ride, then they can be put away.

My style comes from days when we didn't have any of that stuff.
What is needed more than anything is a good mentor. Imo

My method is simple and produces massive yields of top shelf
buds. I'm not forcing you or anybody to use them. I'm just
putting out there what I know from personal experience of
running a gorilla grow that produced 30+ lbs every 80 days;
22+ years ago.

If you want to feel insulted, that's your choice, maybe you're
just thin skinned, & easily offended, I dunno, don't much care.

Not sure why you felt the need to attack me outta the blue,
but I guess it's to be expected on a public forum. I still love
you though bro, no harm, no foul...

Florida_Mike · Sep 3, 2025

KG1 said:
The simplified version would have me see at least noticeable changes if I grew one crop at 35% humidity and another at %70. Even changes as the environment shifted humidity...

I've never reproduced these results in fact I have to really saturate the air for leaves to give any noticeable visible change such as leaf angle.

A more in-depth and frank discussion needs to happen at some point, unless excessively past 30-70% for long periods I've seen no influence or reason to concern myself with humidity.

Although I'm sure it plays a big part and I'm within tolerance for the leaf stomata and overall growth I've come to realise it has some of the least effects on growing indoors.

Also since when did someone have a problem and it got solved by a 20% humidity change? Just don't see that or plants making a miraculous U-turn because of.

Until now just seems like the least important thing on my list, only thing that ever made a difference was altering light temperature and air speed, never had a humidity problem.

I do chuckle at those that run humidifiers in tents or dome seedlings, a lot said by those who do the opposite and produce stellar results despite the wrong humidity.

More data needed, more years to pass for companies to catch up, I mean most are just starting to understand pH and basic things give them time. That's where the debate is for me.

I run domes until al my seedlings break the surface. No pre soak, sewn directly in rockwool. Just a little bit ago was exactly 24hrs and I'm already seeing sprouts. I go by what I know.

JIMKSI64 · Sep 3, 2025

KG1 said:
The simplified version would have me see at least noticeable changes if I grew one crop at 35% humidity and another at %70. Even changes as the environment shifted humidity...

I've never reproduced these results in fact I have to really saturate the air for leaves to give any noticeable visible change such as leaf angle.

A more in-depth and frank discussion needs to happen at some point, unless excessively past 30-70% for long periods I've seen no influence or reason to concern myself with humidity.

Although I'm sure it plays a big part and I'm within tolerance for the leaf stomata and overall growth I've come to realise it has some of the least effects on growing indoors.

Also since when did someone have a problem and it got solved by a 20% humidity change? Just don't see that or plants making a miraculous U-turn because of.

Until now just seems like the least important thing on my list, only thing that ever made a difference was altering light temperature and air speed, never had a humidity problem.

I do chuckle at those that run humidifiers in tents or dome seedlings, a lot said by those who do the opposite and produce stellar results despite the wrong humidity.

More data needed, more years to pass for companies to catch up, I mean most are just starting to understand pH and basic things give them time. That's where the debate is for me.

I also have come to the conclusion that my set in stone humidity limits are self imposed and have limited effect on plants. This came about due to a gnant infestation that had 2 plants in flower and 2 plants with 2 sets of leafs. I had to run at 1.3 vdp to keep the flowering plants going but onoooos you can not run a seedling at 48% it will explode or something.....
Nope.
Actually stability of temp and humidity is much more important. These plants have an incredible ability to adapt to environments. Like any plant they do not like huge changes quickly but I follow guys in sheds at 100 degrees and massive bunkers with a set enviroment that runs strait data lines for days and they all grow pot.

JIMKSI64 · Sep 3, 2025

FloridaMike said:
You've seen vpd readings on my infinity controllers, however;
I pay no attention to it. I don't have a light meter. The other
mike tracks all that, I have no need to.

Why you feel insulted is beyond me. Training wheels are only
needed until you learn how to ride, then they can be put away.

My style comes from days when we didn't have any of that stuff.
What is needed more than anything is a good mentor. Imo

My method is simple and produces massive yields of top shelf
buds. I'm not forcing you or anybody to use them. I'm just
putting out there what I know from personal experience of
running a gorilla grow that produced 30+ lbs every 80 days;
22+ years ago.

If you want to feel insulted, that's your choice, maybe you're
just thin skinned, & easily offended, I dunno, don't much care.

Not sure why you felt the need to attack me outta the blue,
but I guess it's to be expected on a public forum. I still love
you though bro, no harm, no foul...

No foul meant. No attack considered.
I tend to be thin skinned when it comes to tech as that is my whole life. I fought this bias in my work situations when I worked at shops that were poorly tooled up and I was forced into buying tools to do my job or look for a better shop.
Then later when I went mobile for diagnostics and programming I had shop owners try to saddle me with an employee who was gunna watch me fix this car so he did not have to call me again. This was always funny as when I started pulling DSO and logic probes and logic pulsars out of the trunk the poor guy realized I am not going to learn anything useful.
Can I time an engine by ear? Yes I can.
Can I crank an engine over and notice the slight increase in rpm indicating a washed down cylinder from a nissfire? Btdt. How about the dead hole speed bump on cranking from a valve burned or a hole in the piston? Yup yup.
But I still grab the compression tester or run an air hold test or clear the cylinder to make sure.
Tech let's me make sure.

KG1 · Sep 3, 2025

FloridaMike said:
I run domes until al my seedlings break the surface. No pre soak, sewn directly in rockwool. Just a little bit ago was exactly 24hrs and I'm already seeing sprouts. I go by what I know.

Correction, you place domes until seeds sprout, as soon as seedlings they come off so technically not running domes on seedlings.

I did read your thread few days ago, I did too for rock wool germination it dries too quickly sometimes.

Mega impressed with the rock wool cube holder tray, yet to see anyone use it properly though lol. I loved rock wool for germination, place seed exactly the same way in each, barely cover, one shake and some. Soil is a curse to me thinking of all the cool stuff I've run

KG1 · Sep 3, 2025

JIMKSI64 said:
I also have come to the conclusion that my set in stone humidity limits are self imposed and have limited effect on plants. This came about due to a gnant infestation that had 2 plants in flower and 2 plants with 2 sets of leafs. I had to run at 1.3 vdp to keep the flowering plants going but onoooos you can not run a seedling at 48% it will explode or something.....
Nope.
Actually stability of temp and humidity is much more important. These plants have an incredible ability to adapt to environments. Like any plant they do not like huge changes quickly but I follow guys in sheds at 100 degrees and massive bunkers with a set enviroment that runs strait data lines for days and they all grow pot.

I'm a home grower, not looking to push extremes. That is something I mentioned though, unless your pushing an extreme temperature humidity isnt really important.

So I wouldn't recommend people chase that unless they have a very impressive zero issue grow already.

Part the reason I choose not to run co2 even though it could technically yield more.

But are we talking extremes or just the average grow tent and average conditions most of us shoot for.

Why I called for a better type of discussion on vpd. Otherwise the question on leaf offset would be well rounded already.

No argument, hoping in time the subject becomes less of a discussion more of a tool we can all talk about without the obvious confusions.

Bubblegumyum · Sep 3, 2025

beezyacreapiary said:
So I’m borrowing a (firefighter) friends THOR thermal camera to map out my canopy and set my leaf offset temp. I’m running a 4x4 with mostly ac infinity gear. The tent is super efficient and the girls seem to love it, but this $500 thermal camera is telling me that my leaves are -10 to my ambient (controller reading). It feels kind of crazy jacking my tents ambient temperature up to 92 degreees, but the offset adjustment on the controller works the vpd out to my target (.9-1). Idk; it just feels weird, and I can’t find anywhere online where someone’s leaf offset was bigger than -3… should
I trust the gun? Or just set my offset to -2 and forget it? Just looking for outside opinions from my own, a little tired of going back and forth with myself and asking online.
Also, just a note: my acinfinity ir gun and my cheap kitchen gun all read relatively close to the -10 number..

Thanks in advance yall

Sounds like your light is LEDs. How far is the light from your plants?

I've been going down a VPD wormhole since I found out that LEDs make less radiant heat than older types of lights like HPS, so leaf temperatures under LEDs are lower compared with the surrounding air than leaf temperatures under HPS. I think a lot of guidance is based on older types of light

My light is LEDs and my leaf temperature offset is about -6f and my plants look very happy

-10f seems like a lot though. Good to hear the girls don't care!

If it's not the light being too far away then maybe too many fans, as that can reduce your leaf temperature. Plants should be dancing a little wiggle and not have fans pointing directly at them

beezyacreapiary · Sep 3, 2025

Thanks so much for all the replies, I’ll run through them tonight when I get home. Right now I’m leaving it at -3 leaf offset, since besides some slight taco on one, they look fine (to me) I’ll have the thermal gun for another week, if there was any suggestions to testing or troubleshooting- I’ll give it a shot; time allowing. In the meantime here’s a quick shot of the girls
FL- Sour D from Barney’s. FR- Durban poison from Humboldt. BL - dark matter -freebie from multiverse beans ( their genetics)- I biffed this one a bit. BR- Obsidian Drift- another freebie from multiverse, started a couple weeks later than the others, I think she’s a bit of a freak.
It’s been about 15 years since I’ve done this last, and back then I was carrying buckets through swamps to avoid people messing with my crop. I’ve never had the luxury of growing indoors. I love the control and ease- but it’s a whole new world that’s really exciting, but just as confusing. A lot has happened in 15 years. So anyway- I germinated these on 7/25 (except BR- obsidian). Thanks folks!
(These are autos btw- I wanted to dial in the tent with these before I start running photos)

KG1 · Sep 3, 2025

Bubblegumyum said:
Sounds like your light is LEDs. How far is the light from your plants?

I've been going down a VPD wormhole since I found out that LEDs make less radiant heat than older types of lights like HPS, so leaf temperatures under LEDs are lower compared with the surrounding air than leaf temperatures under HPS. I think a lot of guidance is based on older types of light

My light is LEDs and my leaf temperature offset is about -6f and my plants look very happy

-10f seems like a lot though. Good to hear the girls don't care!

If it's not the light being too far away then maybe too many fans, as that can reduce your leaf temperature. Plants should be dancing a little wiggle and not have fans pointing directly at them

Seems a bit squewed though as HPS barely puts out 5% of it's total light as ir radiant heat which isn't much and comparable to lots of LEDs almost.

Biologically a higher leaf temperature works faster and better to a point.

KG1 · Sep 3, 2025

beezyacreapiary said:
Thanks so much for all the replies, I’ll run through them tonight when I get home. Right now I’m leaving it at -3 leaf offset, since besides some slight taco on one, they look fine (to me) I’ll have the thermal gun for another week, if there was any suggestions to testing or troubleshooting- I’ll give it a shot; time allowing. In the meantime here’s a quick shot of the girls
FL- Sour D from Barney’s. FR- Durban poison from Humboldt. BL - dark matter -freebie from multiverse beans ( their genetics)- I biffed this one a bit. BR- Obsidian Drift- another freebie from multiverse, started a couple weeks later than the others, I think she’s a bit of a freak.
It’s been about 15 years since I’ve done this last, and back then I was carrying buckets through swamps to avoid people messing with my crop. I’ve never had the luxury of growing indoors. I love the control and ease- but it’s a whole new world that’s really exciting, but just as confusing. A lot has happened in 15 years. So anyway- I germinated these on 7/25 (except BR- obsidian). Thanks folks!
(These are autos btw- I wanted to dial in the tent with these before I start running photos)

All temp and humidity meters should be completely shaded from all wind and lights direct and indirect.

Getting an accurate air temperature in a hyper reflective bright breezy tent isn't easy to start with.

That temp and rh meter on the floor isn't optimal, finding optimal isn't easy as I said.

Too many variables and science I prefer to run without these days.

I'm off the opinion wind is a sure fire way to stress a plant, airflow should be set to 0.5-1.0m/s. Again hard to read without some Omni directional hot wire anemometer blah blah blah.

Even getting accurate readings and setting things is hard via vpd.

Is my massive leaf offset normal??

Is my massive leaf offset normal??

beezyacreapiary

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Is my massive leaf offset normal??

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