Eye balling brightness

QeedFarmer

QeedFarmer

Member
HI guys,

Im running a 240W Chinese QB 3500K board.
Apogee's too expensive, so Im asking if you guys have a template like
Week #1-end, Light board pulling wattage, High from plant to light
so I can replicate?

Any other form of guesstimation is appreciated too

Thanks
Q
 
Airwalker16

Airwalker16

Well-Known Member
You mean for flowering weeks?
And is this ought the right wattage for your space? Are you in a 2'x4' tent?
 
coreywebster

coreywebster

Well-Known Member
18" full power in flower
20-24" 50% power in veg.

I would ask them guys in the Chinese thread.

I never start seeds under them. I like a 20w cfl for that.
 
E

end_of_the_tunnel

Well-Known Member
Major Blazer said:
Fwiw I thought I was doing well with the eye-ball watt estimate method until I got myself a lux meter and used this link for a ppfd estimate:

Convert Lux to PPFD - Online Calculator | Waveform Lighting

Online calculator to convert illuminance (lux) to PPFD (micromoles per second per meter squared).
www.waveformlighting.com www.waveformlighting.com
Click to expand...
Heres another.

horticulturelightinggroup.com

Converting Lux to PPFD & Measuring Lux with Smartphone

Spectrometer and Quantum Sensor can cost hundreds to thousands of dollars and not every grower can afford them. A Lux meter app on phone can be used to ensure even light spread across canopy and give estimate of Lux. Use a calibrated Lux meter for better accuracy. Just divide the Lux value you...
horticulturelightinggroup.com horticulturelightinggroup.com
 
BluntMoniker

BluntMoniker

Well-Known Member
If you have a smartphone, just download lux meter. I'm sure they're not precise at all, and probably have a swing of +-1000, but it's still enough for you to gauge light/plant distance
 
Dirk8==D~Diggler

Dirk8==D~Diggler

Well-Known Member
BluntMoniker said:
If you have a smartphone, just download lux meter. I'm sure they're not precise at all, and probably have a swing of +-1000, but it's still enough for you to gauge light/plant distance
Click to expand...
Anybody with a lux meter seeing this should download the app and see how accurate it is for those of us without one
 
BluntMoniker

BluntMoniker

Well-Known Member
Major Blazer said:
There are a couple of examples around here showing just how inaccurate and varied the apps can be - not within reasonable margin of error at all

Here's one posted recently https://www.rollitup.org/t/hlg-260qb-ideal-seedling-distance.1008139/
Click to expand...
What do u mean? The OP was using a samsung LUX app, then went out and bought a real one, and said the app was pretty accurate

"Anyway, proper lux meter proved the light is working fine. I have heard Samsung devices are quite superior at detecting lux, and that certainly seems to be the case based on my experience with the iphone apps."

And then others went on to say how samsung is better than iphone, but even if they are slightly off, their still enough to get by on

Even if they are off by 10k lux... it's still enough to dial in your grow, with a bit of common sense and understanding of what your plant should be looking/growing like at the varying stages. Is it perfect? No. Is it better than absolute guesswork? Of course.
 
Major Blazer

Major Blazer

Well-Known Member
Sure, I'll explain myself.

Taking into consideration that at least one phone (or is it the manufacturer as a whole?) performs so questionably, why even air on the side of ambiguity when a lux meter is $20 shipped and provides significantly less ambiguity? When nobody can honestly say that one phone or another will perform to x degree of certainty, how can one even know for sure which phone (or app) will perform reliably. Not only that, consider other outlying factor such as like model phones containing varying parts and versions of OS's, it just makes a lot more sense *to me* to avoid using a smartphone camera as a lux meter.
 
BluntMoniker

BluntMoniker

Well-Known Member
Major Blazer said:
Sure, I'll explain myself.

Taking into consideration that at least one phone (or is it the manufacturer as a whole?) performs so questionably, why even air on the side of ambiguity when a lux meter is $20 shipped and provides significantly less ambiguity? When nobody can honestly say that one phone or another will perform to x degree of certainty, how can one even know for sure which phone (or app) will perform reliably. Not only that, consider other outlying factor such as like model phones containing varying parts and versions of OS's, it just makes a lot more sense *to me* to avoid using a smartphone camera as a lux meter.
Click to expand...
I can agree with that :). Plenty of viable points in terms of quality and accuracy from one device to another.. hard to get a comparison to even know how inaccurate your own device is.
 
Major Blazer

Major Blazer

Well-Known Member
So with life moving at a snail's pace and boredom being the mother of invention, I decided to see if my phone is working to a degree of certainty when compared to the meter.

Phone = Google Pixel 3; App = Lux Light Meter Free (Doggo Apps) - measured 42222k at my canopy in the middle of the tent
Urceri lux meter Amazon special measured just over 47k at the canopy in the middle of the tent

Using the link I posted with the 90cri 3k Led vaiable the readings are:
Phone 803.38: umol/s/m2 vs Meter: 894.29 umol/s/m2

So in my case, it's close enough to me. If there's a repo anywhere where people are tracking their phones for this purpose, lmk and I'll add my findings to the list
 
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