New Light Meter

dolchmann

dolchmann

Active Member
I have had several Great Grows.
I have never used a light Meter.
I want to begin to fine tune my tent. 4x4 by 80 inches tall.
Using Viparspectra Pro Series PS2000 one on each side
and a PS1500 across the back. I think it is over saturation.
And I also think I could do without the PS1500. But its my layout,
which is caused by my physical disablities. I need to fully enter the tent.
I am asking for a round about lumen setting, I think 2700 is good.
Does anyone with a light meter agree with that???

Second question, is it best to turn the lights down or just raise them.
I know I am leaving out information. My plants are auto flower.

But I am asking for a good starting point before I do all the math.
Thanks to any one who can help me. Does 2700 lumens sounfd good until I really dig into it.
Which might be a few weeks.
J
 
D

Delps8

Well-Known Member
To get the PAR values from your lux readings, multiple the readings by 0.015. That will get you very close to the actual PPFD value. I've tested a Uni-T light meter against my Apogee with a Vipar Spectra XS-1500 and a Growcraft X2 and the values ranged from 0.014x and 0.015x. I don't regret spending the $$ on the Apogee but, for most growers, a lux meter is all that's needed.

Re. Photone - tested it a couple of times and would only use if my Apogee and my light meter were on the fritz. When I tested the Korona (the original name of Photone) against a blurple, it failed completely. Emails with the programmer couldn't resolve the issue. When I tested it against my X3, it was consistently 16% high. The fact that it's consistent is good but I'm still not a fan - the paper shield is a kludge plus I'd rather use a $35 light meter than wave a $1000 iPhone around.

Re. 27k lux - that's only 405µmols. Cannabis will grow between 64µmols (the "light compensation point") and 800-1000 µmols (the "light saturation point"). It seems that a lot of growers run their grows at 500-600 µmols. The Photone site and Migro recommend levels in that range. Light manufacturers recommend higher levels, usually at the LSP. Researchers show, repeatedly, that, basically, more light = more weed of better quality. I get my grows to the LSP as soon as possible. Compared to the cost of weed, even at 31¢ per KwH, what I pay for electricity in SoCal, the difference between running my light 20/4 for a month is only $15 more to run it at 330 watts vs backing it down to 250 wats. In research paper"The Effect of Light Spectrum on the Morphology and Cannabinoid Content", the yield curve graph illustrates that an of 50µmols results in about a 4.5% - 5% increase in yield. I'm happy to spend the $15.

Re. 62k - you're rocking it! Great. As long as the other factors in the grow environment are squared away, cannabis will thrive at that light level. Good to see.
 
D

Delps8

Well-Known Member
Star Dog said:
Hey buddy, that's without Co2.

Eta in the photone app it recommends a trusted meter for calibration.
View attachment 5234550
That happens to be the one that i have.
View attachment 5234551
The figures work out to around 1050 umols.
Click to expand...
1050? That would be a factor of 1050/30800=0.3398≈0.34 which is an outlier for the data that I've worked with.

Check the factors on the second tab of the Excel document.

[time passes]

Hmm, can't attach an Excel document so I've had to paste in screenshots. :-(

1670352641225.png


1670350570459.png
 
Star Dog

Star Dog

Well-Known Member
Delps8 said:
1050? That would be a factor of 1050/30800=0.3398≈0.34 which is an outlier for the data that I've worked with.

Check the factors on the second tab of the Excel document.

[time passes]

Hmm, can't attach an Excel document so I've had to paste in screenshots. :-(

View attachment 5234592


View attachment 5234585
Click to expand...
Sorry bud I'm not sure about the technical side of things, i watched a clip on YouTube and the chap had taken various measurements with a apogee meter and a lux meter, he said if you multiply the lux by 0.015 its a good enough guide for the home grower.

I used this convertor.

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
 
D

Delps8

Well-Known Member
Star Dog said:
Sorry bud I'm not sure about the technical side of things, i watched a clip on YouTube and the chap had taken various measurements with a apogee meter and a lux meter, he said if you multiply the lux by 0.015 its a good enough guide for the home grower.
Click to expand...
Shane, the owner of Migro, has a video out on this. Perhaps that what you're referring to.

If you read through what I posted, you will see that is the point that I'm making. The data in the second posting show the different factors to provide the reader additional information about what these numbers mean and I have provided sources to allow the user to verify the accuracy of the data that I've provided.

Star Dog said:
I used this convertor.

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...
If you feel that's a good source, you should just run with that but I would recommend that readers disregard the values generated by that page because a quick check shows that some of the values are very wrong.

None of the results on the Wave Form Lighting page use the 0.015 factor. That's understandable because 0.015 not meant to be accurate, it's just "close enough". The actual value for the factor varies with the light source but some of the values are incorrect. A few of them are in the ballpark with data from HLG, Apogee, and other sources on the Web but I would find a source other than this page.

Their factor for sunlight is 0.023 which is completely whacked compared to the value that Apogee provides, which is 0.0185. In fact, the Apogee page uses 108000 lux as their example since full sunlight is about that value. Per Apogee, 108k lux is 2000µmols vs 2484 from Wave Form Lighting. The Wave Form Lighting value is 24% high and, since there are so many other options to convert Lux to PPFD I would not use that site.

1670359903416.png

The factor values from HLG are here and from Apogee are here.

If the conversion factor is too high the calculated PPFD value will be too low. If the light meter reading of 30900 is being converted to get a PPFD reading of 1050µmols, a grower will probably turn down the light by at 10 or 20% because most growers are reluctant to feed their plants that well (even though cannabis rocks at 1kµmols). If they turn down their light, their plants will be getting in the region of 400µmols and they may not be able to tell that they are severely under-lighting their grow.

The actual PPFD for that light level is much lower, to whit — 30900 lux * 0.015 = 464 and, if you reduce that by, say, 15% you're down to only 394µmols. That's seedling territory but, since cannabis will grow at light levels > 64µmols, the plants will chug right along. It won't "hurt" the plants but you get tend to get tall plants, reduced plant yield, reduced crop quality, greater internodal spacing, reduced amounts of foliage, etc., etc.

In short, if I needed to get an estimate of the PPFD from a "white" LED grow light and I had a lux reading , I'd go with a 0.015 conversion factor. I was using another light source, I would avoid using Wave Form Lighting and go with the data from Apogee or another source.
 
1

1212ham

Well-Known Member
1212ham said:
The accuracy depends on the phone used. Android version is still in beta testing and won't go over 400 something on my phones.

I bought this for $30. It matches my Tasi TA8130 at 38,000 lux.

Click to expand...
I have no idea how consistent lux meters are, the UNI-T Shane tested in the video might read differently than the UNI-T I bought.

Correction: I did a controlled test and the TASA reads about 10% lower than the UNI-T.
 
Last edited:
1

1212ham

Well-Known Member
PopAndSonGrows said:
Are you using a case or screen protector on your phone? Could be skewing readings. Maybe trade your Adoid for an Android, lol
Click to expand...
A case or protector isn't going to cause a light sensor to hit a hard limit.

I tried 4 apps, PPFD Meter, Tent Buddy, LUX, and Photone. The first three max at 32,767 lux but Photone maxed at 22,900. Exact same numbers on two cheap Samsung's.

WTF? They all get the same data from the phones light sensor...... so why is Photone wildly different?

Here's Photone's solution. :roll:

growlightmeter.com

Fixing the Built-in Light Sensor’s (ALS) Limitation

A workaround to fix the built-in light sensor's (ALS) limitation
growlightmeter.com
 
Last edited:
farmingfisherman

farmingfisherman

Well-Known Member
1212ham said:
A case or protector isn't going to cause a light sensor to hit a hard limit.

I tried 4 apps, PPFD Meter, Tent Buddy, LUX, and Photone. The first three max at 32,767 lux but Photone maxed at 22,900. Exact same numbers on two phones.

WTF? They all get the same data from the phones light sensor...... so why is Photone wildly different?
Click to expand...
My Google phone maxed out so I put the luxx app on my older Samsung tablet and have yet to max out it's readings. Guess Google phones don't use the best hardware.
 
You must log in or register to reply here.
Top