Lux and height

Wizzlebiz

Wizzlebiz

Well-Known Member
Good morning folks.

Gonna start with this disclaimer. I'm new to tent growing. Asking questions to get a better understanding.

When it comes to height of my light vs FC or lux.

Say my light is supposed to be 30 inches away which would give a 150 fc or 15000 lux. Now say I have it 15 inches away but dimmed to 50% and the lux is 15000 does the distance actually matter anymore if the lux is correct?

I understand to close can ruin a footprint. That I get. But what if its not too close to ruin a footprint?

Again I'm new to grow lights. I have only grown outdoors.

Thanks,
Wiz
 
HydroKid239

HydroKid239

Well-Known Member
Wizzlebiz said:
Good morning folks.

Gonna start with this disclaimer. I'm new to tent growing. Asking questions to get a better understanding.

When it comes to height of my light vs FC or lux.

Say my light is supposed to be 30 inches away which would give a 150 fc or 15000 lux. Now say I have it 15 inches away but dimmed to 50% and the lux is 15000 does the distance actually matter anymore if the lux is correct?

I understand to close can ruin a footprint. That I get. But what if its not too close to ruin a footprint?

Again I'm new to grow lights. I have only grown outdoors.

Thanks,
Wiz
Click to expand...
Haven't tried to sit the light closer, but I have heard the weaker the intensity the closer it should be.
I kept my seedlings under 4x 6500k cfl til 3 sets of leaves grew out. Then I put the sf1000 at 24 inches 40% power.
With better led I wouldn't keep it too close to the babies. Not sure about the lux or anything like that. Only what I've done, and how it turned it out.
 
kovidkough

kovidkough

Well-Known Member
my Samsung might not be super accurate but its a lux meter app and it is telling me that 3ft from my 600w hps is 24k lux so sounds somewhat accurate
 
Wizzlebiz

Wizzlebiz

Well-Known Member
kovidkough said:
this guy is great his videos are based on science and he is also the creator of a light sensor company
Click to expand...
Just watched this. And yea that makes tons of sense. Luckily we have technology in out phones that see all the spectrums including blue and red equally.

They do have external adapters for the phone for quantum readers if you wanna get truly precise though.
 
J

Jimbo the Gael

Well-Known Member
Due to an equipment failure back when I was growing indoors I had to use an underpowered LED panel for one of my plants. I just put it closer to the canopy and the plant did just fine.
 
Crackiller

Crackiller

Active Member
My question because I’m new is what indicators show height is good? and what’s shows the height is too low or too high?
 
athlete

athlete

Well-Known Member
Well, if you want my data...

I just stood under a normal ceiling light.

Galaxy 20 using Lux Light Meter = 210 lux
Hanna HI 97500 = 153lux

At 5000lux on the Hanna, LuxLightMeter was >= 500lux over.
 
JoeBlow5823

JoeBlow5823

Well-Known Member
Wizzlebiz said:
Say my light is supposed to be 30 inches away which would give a 150 fc or 15000 lux. Now say I have it 15 inches away but dimmed to 50% and the lux is 15000 does the distance actually matter anymore if the lux is correct?

I understand to close can ruin a footprint. That I get. But what if its not too close to ruin a footprint?
Click to expand...
In this specific comparison, your footprint will be half the size, but your basically getting the same amount of light in that footprint. Personally i would just keep it at 30'' and 100% unless your having heat issues but it sounds like you are running a pretty small light. Your electric costs are probably 1-2 cents per hour at 100%
 
Wizzlebiz

Wizzlebiz

Well-Known Member
JoeBlow5823 said:
In this specific comparison, your footprint will be half the size, but your basically getting the same amount of light in that footprint. Personally i would just keep it at 30'' and 100% unless your having heat issues but it sounds like you are running a pretty small light. Your electric costs are probably 1-2 cents per hour at 100%
Click to expand...
It was honestly not about energy consumption and more about using the dimmer to control intensity instead of moving the light which would just be easier.
 
M

mnw

Member
Hi everyone,

Don't want to open a new thread, this problem is very similar to mine. I have changed my HPS bulb recently, it is 250W and 32.000lumen. I have 60x60cm (2ftx2ft) grow tent. I have grown three in my balcony, then i took two of them in to the tent for flowering. Third one which stays at the balcony is growing without any problems.

But other two are suffering from light burn i guess. They are in the 4th week of flowering, I have recognised burning parts at the end of week 2. First I stopped giving nutrients for a week, but nothing has changed.

Distance between bulb and top of the plants is 25cm (10"). Temperature on the top is 28C max, generally 26-27C. I think problem is not the heat, it is the lux. I have calculated lux value, it is 179.000 something. I have used this site but i'm very suspicious about the result.

Lux/Lumens Calculator: How Much Light Do You Need?

Use our lux/lumens calculator to determine how much light is needed for your industrial lighting application.
www.bannerengineering.com www.bannerengineering.com

Anyway what can you suggest for bulb height or decreasing lux value. Or even calculate it right at the first place. I have attached a few photos.
 

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C

ComfortCreator

Well-Known Member
In an ideal setting with most lighting, 24" away and up to 75k lux is imo ideal.

Many lighting systems are in a brochure where they say you can be 12" away. Or 18" for example. This may be true and I have had plants that close to strong lighting.

50k lux is a good flowering number. It's enough to grow well.
 
M

mnw

Member
Thanks mate.

I observe claw leaves at the bottom or middle parts of one plant. I think it is ph or nitrogen toxicity. Well tops may be lightburnt or windburnt still, there is something wrong with soil ph or nutrients. I will recalibre ph meter again, go with %50 of supposed nutrients. Also i took out slightly better looking one and give other one more room and bend a little

Anyway will wait and see
 
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