# LED light: lux vs ppfd, height vs intensity?

• None

#### Potsquatch

Trying to definitely understand how to best measure light, specifically in an LED context. Two questions:

1) I've seen equally strong preferences for measuring light in lux, using free apps, or in ppfd, using math I don't understand. Is lux approximate while ppfd is much more accurate, or do they measure different things? I get confused when ppfd measurements bring in a time factor (e.g. not just how much light is hitting a plant, but how much is hitting a plant per second/day/whatever and why it matters).

2) With LEDs (full spectrum, not blurple, thinking of Spider Farmer lights specifically), I understand they have a lower light "intensity" (might be the wrong word, but run with me here) than other light types, meaning the "higher quality" light with stronger canopy penetration is much closer to the diodes. How do you measure that with dimmable LED setups?

Trying the gauge if there's a difference between LEDs very close to a plant on a lower setting (dimmed to 20-30%) vs. further away at the highest setting (100%), and if there's a way to calculate the sweet spot--or if it even matters, because the manufacturer recommendations already did the hard work of figuring that out.

Manufacturer specs for the SF-1000 attached for reference. So much of the discussion around this predates full spectrum LEDs, it's tough to translate.

Worth noting the official product page includes lumens, which for the SF-1000 is 16439Lm±5%@AC120V (AC120V is a standard US 110v wall outlet).

#### Anthem

If you would like to understand this information the best way I have seen it explained was on a You Tube Video, go to you tube and look up Bruce Buggee, he has a video titled PPFD or something like that that is about 20 minutes long and explains everything in regards to lighting and cannabis

#### lvstealth

Supporter
nothing tells you like the plant when the light is right.

because the cost of the meters is significant, i just use an app. it is not so accurate i would guess, but it is a nice starting point. set it for what you think your plant needs in the stage it is in and watch it. it will show you it loves the light or hates the light or is just ok with it all. you lower/raise till you get them just where you want them.

with that method it doesnt really matter what your numbers are, just that when it is at xxx then your plants like it, so next time you set it to xxx. you will find a plant here and there that likes more light or less than you chart it, so you just move it a bit. doing it like that you will be within an inch of where you need and some fine tuning and youre there!

#### growsince79

Back in the late 70s early 80s people had the same question. Turned out HID lighting worked better than equal amount of florescent light. They also proved white light was better than blurple grow lux.

#### Habosabin

I like DLI. It takes into account total light received in a 24hr period.

#### Frankster

##### Seshat; Goddess of Wisdom, Knowledge, and writing.
Supporter
I've spent literally Thousands of \$\$\$ buying a plethora of various LED's over the past decade. I've had them custom built.

The lights here at SF are as good as any made, and blue/red light isn't even in the same ballpark with these diodes. It's like apples and oranges. Those blue/red lights are so very inefficient and obsolete it's really not a discussion at this point.

PPF and PPFD are the main concepts you need to grasp here. Nothing more.
• PPF - photosynthetic photon flux
• PPFD - photosynthetic photon flux density
Anything Samsung full spec is the standard for today, period. There are many imitations, but the LM301 any series are all top notch. The 301H are the best overall. You want 660 range + IR + UV A+B also, if possible. It's all about the ratio's at this point, and most important, configuration.

Look at spider farmers SE series lights....

#### GrowHobo

I've spent literally Thousands of \$\$\$ buying a plethora of various LED's over the past decade. I've had them custom built.

The lights here at SF are as good as any made, and blue/red light isn't even in the same ballpark with these diodes. It's like apples and oranges. Those blue/red lights are so very inefficient and obsolete it's really not a discussion at this point.

PPF and PPFD are the main concepts you need to grasp here. Nothing more.
• PPF - photosynthetic photon flux
• PPFD - photosynthetic photon flux density
Anything Samsung full spec is the standard for today, period. There are many imitations, but the LM301 any series are all top notch. The 301H are the best overall. You want 660 range + IR + UV A+B also, if possible. It's all about the ratio's at this point, and most important, configuration.

Look at spider farmers SE series lights....
They are doing a bogo sale right now.

#### goingtoguano

This online calculator is pretty interesting.

#### lvstealth

Supporter
is that number that important? it is quite a bit for any accurate meter to find the number, you should weigh the importance of that number against the cost to get it.

then you set it to that number and they dont like it - so you have to watch and adjust. i have two the same strain, planted the same time and treated the same, one wont get happy till its over 80f and lots of light, over 70k lux, the other doesnt seem to care what temp or light. a different strain right in front of those doesnt mind lots of light, but hates when it is over 78f. so any way you do it, great meter that cost a fortune, or just open your eyes and watch them tell you just what they like.

anyway, just my opinion, i dont think, if you just pay attention, you need a meter to give you a number to achieve this. start with the app, or even what the manual that came with the light says, then watch your plants and act accordingly.

if you get a meter, you still end up having to watch the plants to dial it in, not any two are the same.

if you arent watching the plants, no meter is going to help

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