measuring PAR using a LUX meter vs Apogee results

[Jonreefer]

So is that why 30 works perfect. This thing reads half so that comes out to 60 lol I am just spit balling

 

[saltyfilmfolks]

So is that why 30 works perfect. This thing reads half so that comes out to 60 lol I am just spit balling

Hahahaha!!!

I honestly think the only light you cold get a 30 from would be a pink grow light. I’ve asked a couple folks to do it for me but ....

 

[Scrubber_steve]

So @saltyfilmfolks i just took my LUX meter outside to measure the sun.
Its summer here 11.30 am standard time sun is directly above, no cloud

Reading is 1261 x 100 = 126,100 LUX.
Does that sound right?

 

[Jonreefer]

Might order another unit from different company to see how it compares

 

[Scrubber_steve]

So @saltyfilmfolks i just took my LUX meter outside to measure the sun.
Its summer here 11.30 am standard time sun is directly above, no cloud

Reading is 1261 x 100 = 126,100 LUX.
Does that sound right?

Just did the test more accurately & got 1320 x 100

 

[saltyfilmfolks]

Just did the test more accurately & got 1320 x 100

What meter ?

Should be no more than about 100,000

 

[Scrubber_steve]

What meter ?

Should be no more than about 100,000

 

[saltyfilmfolks]

Are you in the desert?

Lol

 

[Scrubber_steve]

Are you in the desert?

Lol

On the coast south of Sydney, not desert.

 

[saltyfilmfolks]

On the coast south of Sydney, not desert.

Hmm. Curious

 

[Scrubber_steve]

Hmm. Curious

Lux meter perhaps not so accurate

 

[saltyfilmfolks]

Lux meter perhaps not so accurate

Hard to say. I’d actually have to be there. Reflection etc etc. poor qc. dunno.

 

[Scrubber_steve]

Wiki says
120,000 lux Brightest sunlight

 

[WallyB]

I got one of these Lux Meters, made for use under Water. (much cheaper than a Apogee Quantum Meter)
http://www.milwaukeeinst.com/site/component/content/article/36-standard-portable-meters/88-products-g-standard-portable-meters-g-mw700-wp

Used it when I had MH Bulbs since coversion to PAR was pretty accurate with a Table I found.

It's been collecting dust but maybe time to dig it out again, since I did covert from MH to T5/LED

This Table has MH & somewhat T5.

http://www.egc.com/useful_info_lighting.php

Yet, I think with LED's and How you set (colors/intensity)........conversion gets more complex.

 

[oreo54]

Unfortunately, that’s not how it works.

The reason the conversion constant number is what it is , is due to the spectrum of the unit.
The conversion constant of a t5 is about 50 , the sun is 54.

To get 30 would not make sense

https://www.apogeeinstruments.com/conversion-ppfd-to-lux/

W/ really heavy blue (or red but irrelevant for the most part) you could probably go that low....or at least closer.. like 40-ish
Especially w/ high blue content LED's

Old Apogees had their own errors in that range as well....but irrelevant for his discussion.

12000k-ish mh's or 50/50 b/w led shouldn't be an issue though for the 60-ish
https://www.apogeeinstruments.com/conversion-ppfd-to-lux/


MUCH depends on spectrum.......
As to 125,000 Lux at sea level in Australia..in the summer (jealousy) ?????

Meter inaccuracies..mostly.. 25% -ish .
High ranges and low are always problematic for cheaper devices.. Usually gets less as one goes "midrange"..

fun w/ math..Easy to get a conversion factor if you sum up the spectrum.. (sorry, mild sarcasm)

http://docs.agi32.com/AGi32/Content/adding_calculation_points/PPFD_Concepts.htm

note the listed ones are conversions for KILOLux so need to divide by 1000 then multiply.

None are blue heavy lights though..
Fun one.. "pure blue" led lux to PAR is ....9!!!
hort. lamp (blue/red) is 11..
https://www.waveformlighting.com/horticulture/convert-lux-to-ppfd-online-calculator