Lux to par graph/conversion

[SteakBags]

What do the experienced LED people think about the accuracy of these graphs? For my specific situation I’m using a 65w 4000k HLG 65.

If I buy a lux meter and multiply my lux by 0.024, am I going to be in the ballpark of an accurate PAR reading?

I included the graphs and video from which they came.

 

[Snob]

don’t waste your time. just buy a quality par reader.

 

[SteakBags]

don’t waste your time. just buy a quality par reader.

Looking to avoid the few hundred dollar price tag

 

[Snob]

Looking to avoid the few hundred dollar price tag

Then Just save up and wait. Lux is not made to measure LED's. There is a reason the PAR meters are expensive. I dont know how nerdy you are, but there are people on the tube that build these themselves.

 

[SteakBags]

Then Just save up and wait. Lux is not made to measure LED's. There is a reason the PAR meters are expensive. I dont know how nerdy you are, but there are people on the tube that build these themselves.

I don’t need it to be exact, and there are conversions for lux to par which is what I’m trying to figure out. I’m growing 2 fairly small plants in my closet, if I can dial in where my light needs to be without spending $500 I’m going to try and go with the cheaper route.

The issue is my LED being too close because I’m limited vertically (36” floor to light) ...if I can get a rough estimate on lux to par I can figure out if and how much I need to dim it down.

 

[.Smoke]

I don't use Led but...

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

Allows you to enter what kind of light you're using.

 

[SteakBags]

I don't use Led but...

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

Allows you to enter what kind of light you're using.

I saw this and another calculator online, but they don’t correlate with the graphs which were made using an accurate par meter.

 

[.Smoke]

I saw this and another calculator online, but they don’t correlate with the graphs which were made using an accurate par meter.

I think that's the problem of not having a PAR meter for Led.

Yes, we all know an Eye Hortilux HPS bulb is a bit brighter, but the difference in HID bulb variance I'm guessing is a lot less than the variance between a top line Samsung diode compared to a bottom of the barrel one. Making it much harder to get an average to base an equation off of.

Unfortunately, the answer seems to be that your expensive light is gonna need an expensive meter.
Yet another reason that turned me away from Led.

 

[Moflow]

If you buy a lux meter just take a reading 18" away from the light and whatever lux reading it says will be the equivalent of 290 umols/m2/s
These Par Maps below will tell you all you need to know for growing.
I would say round 22-24" for seedlings, early vegging plants


This Map below is 12" from the sensor
So around 14" for late vegging plants
12" early flowering of plants.
8- 10" away for mid late flowering.

Problem solved.

 

[SteakBags]

If you buy a lux meter just take a reading 18" away from the light and whatever lux reading it says will be the equivalent of 290 umols/m2/s
These Par Maps below will tell you all you need to know for growing.
I would say round 22-24" for seedlings, early vegging plants
View attachment 4617454

This Map below is 12" from the sensor
So around 14" for late vegging plants
12" early flowering of plants.
8- 10" away for mid late flowering.
View attachment 4617455
Problem solved.

My head hurts from researching this shit literally all day, I completely forgot about using that par map as a reference. Thanks for thinking for me lol

 

[SteakBags]

If you buy a lux meter just take a reading 18" away from the light and whatever lux reading it says will be the equivalent of 290 umols/m2/s
These Par Maps below will tell you all you need to know for growing.
I would say round 22-24" for seedlings, early vegging plants
View attachment 4617454

This Map below is 12" from the sensor
So around 14" for late vegging plants
12" early flowering of plants.
8- 10" away for mid late flowering.
View attachment 4617455
Problem solved.

so for shits and giggles lets say it read 20,000 lux at 18”, 20,000/290 = 68.96 ....so round up to 69, would that be my conversion number for any lux reading under this light?

 

[Moflow]

According to hlg 4000K at 290 umols = 20167 lux

69 sounds about right

 

[Renfro]

What do the experienced LED people think about the accuracy of these graphs?

The real question is the accuracy of the meter. Most meters don't accurately quantify only the spectra that the plants use (PAR). Most read two different light sources as apples and oranges making any comparison pointless. An exception to that is a quality PAR meter like the Apogee MQ-500. This meter can read a HPS light or a LED light and make apple to apple numbers out of that.

 

[Renfro]

Looking to avoid the few hundred dollar price tag

Then skip the meter because you are wasting money to save money. I grew the first 28 years of my career without a light meter and now that I have an apogee it's sitting on the shelf collecting dust.

 

[lukio]

What do the experienced LED people think

imo, a 20 dollar lux meter and the conversion charts to find hotspots and roughly check spread is all you need.

as mo said, seems about right

 

[SteakBags]

The real question is the accuracy of the meter. Most meters don't accurately quantify only the spectra that the plants use (PAR). Most read two different light sources as apples and oranges making any comparison pointless. An exception to that is a quality PAR meter like the Apogee MQ-500. This meter can read a HPS light or a LED light and make apple to apple numbers out of that.

From what I’ve read it’s only the blurples and that color light that the lux meters won’t read, correct me if I’m wrong but wouldn’t I be fine with my white 4000k spectrum?

 

[SteakBags]

@JoeBlow5823 any input? Thought I saw you talking about meters somewhere

 

[Renfro]

From what I’ve read it’s only the blurples and that color light that the lux meters won’t read, correct me if I’m wrong but wouldn’t I be fine with my white 4000k spectrum?

They will read HPS differently than MH or CMH, they read all lights differently. They don't measure PAR spectrum, and therefore you can't convert the LUX numbers to PAR numbers. It's just that simple. PAR means photosynthetic active radiation.

 

[Renfro]

Unless you are testing lights extensively then you don't need to even have a light meter. Even for checking if a bulb is losing output you don't need a meter, it's predictable but in that case you don't need any PAR numbers, just know what it read new and what it reads now on a given meter. Save the money on a meter to quantify light and use it to purchase something truly useful like a quality pH meter or a better light, you know, something that will actually increase yields.

 

[JoeBlow5823]

I like having mine.... I find when Im reading over 55-60k lux, its to bright. I mostly will be using it to train my plants in my 5x5. Keep them low in the middle hot spot and tall on the outsides.

I also compared my double end 1000w HSP to a friends single end and found my light to be a solid 20-30%