"White" versus "Purple" grow lights

O

OGHomeslice

Active Member
So, I have this aquarium. I have very successfully been growing plants in/on the top of it to suck out the nitrates to make water changes unnecessary. Its actually working too good - nitrates are at zero meaning I need more fish lol.

Anyways, check out the picture below. On the left, I've had mostly "low watt" LED grow lights, like 9w or something. I just the other day added a much stronger (white) one. On the right I've had those three strong LEDs, that are like 45 watts each. You can't really do a good comparison here, as the plants on the right are beans, which apparently can thrive in low-nitrate environments, while the plants on the left are like okras and chilies, which apparently can not. But I'm just curious - why are some LED lights, apparently the weaker ones, purple colored, while others, apparently the stronger ones, are white or close to it? What should I be looking for in a good LED - purple, or NOT purple?

Thanks so much!!!

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OrganicBudz

OrganicBudz

Well-Known Member
You can have 2 light same wattage but one has a better growing spectrum and itll lean towards that. I hope you don't expect to grow much with those lights.
 
S

SDS_GR

Well-Known Member
To make things simpler and shorter :

Having only the blue and red part of
the photosynthetic active radiation spectrum can grow lots of different plant species .Mainly those that are
pretty compact stature-wise and do not need particularly high flux densities in order to grow with vigor .

Plant species that have bigger volume
( with branches and/or dense foliage )
and need full sun power in order to grow close to their full potentional ,need an artificial lighting that contains
the green part of the PAR spectrum.
Green light is the main fuel of photosynthesis at the older and larger leaves ( quite a few call this phenomenon “penetration “ and think that HID lighting offers better light penetration than LEDs do .Well that ain’t that far from truth ... HID lights do emit -mainly -a rich amount of green light... ) .Green light also regulates the metabolism of the plant .
Without it, the photosystems of the plant will suffer from photoinhibition
caused by blue light and photosaturation caused by red light ,
when both are radiated at high flux densities, for at least 12 hours per day.

Red+Green+Blue = White

White light was for million years the best available option for photosynthesis.

Purple ,blurple and magenta combos are very good for deep space exploration food & oxygen production chambers ,greenhouse supplemental or intracanopy lighting ,gothic christmas trees and disco -80’s tribune parties ...
 
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PJ Diaz

PJ Diaz

Well-Known Member
SDS_GR said:
To make things simpler and shorter :

Having only the blue and red part of
the photosynthetic active radiation spectrum can grow lots of different plant species .Mainly those that are
pretty compact stature-wise and do not need particularly high flux densities in order to grow with vigor .

Plant species that have bigger volume
( with branches and/or dense foliage )
and need full sun power in order to grow close to their full potentional ,need an artificial lighting that contains
the green part of the PAR spectrum.
Green light is the main fuel of photosynthesis at the older and larger leaves ( quite a few call this phenomenon “penetration “ and think that HID lighting offers better light penetration than LEDs do .Well that ain’t that far from truth ... HID lights do emit -mainly -a rich amount of green light... ) .Green light also regulates the metabolism of the plant .
Without it, the photosystems of the plant will suffer from photoinhibition
caused by blue light and photosaturation caused by red light ,
when both are radiated at high flux densities, for at least 12 hours per day.

Red+Green+Blue = White

White light was for million years the best available option for photosynthesis.

Purple ,blurple and magenta combos are very good for deep space exploration food & oxygen production chambers ,greenhouse supplemental or intracanopy lighting ,gothic christmas trees and disco -80’s tribune parties ...
Click to expand...
I don't think that was simpler, or shorter. In fact it's not even all that accurate.
 
2Hearts

2Hearts

Well-Known Member
Plants have receptors for all the colours, turn more on and you get more growth.

Blurples are too heavy in the red and blue, white has plenty of red and blue but also a lot of the other colors.

Monochromatic light would be the worst.
 
S

SDS_GR

Well-Known Member
PJ Diaz said:
I don't think that was simpler, or shorter. In fact it's not even all that accurate.
Click to expand...
There are more than a few of research papers that back up what i’ve stated to the last word
(Hence my post is the shorter and simpler version ... )
Please post at least one paper that will prove the inaccuracy that you ‘ve spotted.
 
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PJ Diaz

PJ Diaz

Well-Known Member
SDS_GR said:
There are more than a few of research papers that back up what i’ve stated to the last word
(Hence my post is the shorter and simpler version ... )
Please post at least one paper that will prove the inaccuracy that you ‘ve spotted.
Click to expand...
Sure. First of all HPS is not mainly a green light, feel free to prove me wrong. Some of your assertions about green light are definitely highly debatable.

One thing you said seemed a bit silly to me in general:
"Red+Green+Blue = White"

While I guess technically this is true, it doesn't speak to the other colors in the spectrum and "green" is redundant since it's a mix of blue and yellow (yet you forgot to mention yellow at all), and certainly doesn't speak to light at the far ends (or outside of) of the visible spectrum.
 
cannabineer

cannabineer

Ursus marijanus
PJ Diaz said:
Sure. First of all HPS is not mainly a green light, feel free to prove me wrong. Some of your assertions about green light are definitely highly debatable.

One thing you said seemed a bit silly to me in general:
"Red+Green+Blue = White"

While I guess technically this is true, it doesn't speak to the other colors in the spectrum and "green" is redundant since it's a mix of blue and yellow (yet you forgot to mention yellow at all), and certainly doesn't speak to light at the far ends (or outside of) of the visible spectrum.
Click to expand...
That is the case for subtractive (reflected) colors. But for additive (emitted) colors RGB is the current standard.

1590900609071.jpeg
 
PJ Diaz

PJ Diaz

Well-Known Member
cannabineer said:
AFAIK the emissive set is a property of light on the context of the physiology of human vision.
Click to expand...
The thing is with additive mixing techniques you can't actually get all colors to be produced by mixing only RGB. This can be seen in real life applications. In theatrical situations, you can never produce a real yellow from a RGB mixing unit, which is why the higher end LED theatrical units add yellow diodes.
 
PJ Diaz

PJ Diaz

Well-Known Member
PJ Diaz said:
The thing is with additive mixing techniques you can't actually get all colors to be produced by mixing only RGB. This can be seen is real life applications. In theatrical situations, you can never produce a real yellow from a RGB mixing unit, which is why the higher end LED theatrical units add yellow diodes.
Click to expand...
Check out this link for the ETC Color Source which is often used in the theatrical lighting industry. You will see that they have two different versions, and it shows which color ranges can be achieved with each version: https://www.etcconnect.com/Products/Lighting-Fixtures/ColorSource-PAR/Deep-Blue.aspx
 
cannabineer

cannabineer

Ursus marijanus
PJ Diaz said:
The thing is with additive mixing techniques you can't actually get all colors to be produced by mixing only RGB. This can be seen is real life applications. In theatrical situations, you can never produce a real yellow from a RGB mixing unit, which is why the higher end LED theatrical units add yellow diodes.
Click to expand...
And yet my RGB screens on my TV and my phone do a pretty good job. The whiteness of white is very good. Ever look at one with a magnifier? Granted the G is sort of a yellow-green.

I know high-quality photos in magazines use a four-color process. I’m guessing the theatrical units you mention are similar in principle. It makes for a more efficient rendition of perceived color, perhaps ... or a way to add violet to an optimal four-color set.

Im sort of blue-skying here ...
 
Lockedin

Lockedin

Well-Known Member
cannabineer said:
That is the case for subtractive (reflected) colors. But for additive (emitted) colors RGB is the current standard.

View attachment 4581380
Click to expand...
RGB is the current standard because of camera sampling chips and monitor phosphors.
Most broadcast cameras sample colors as follows - Green 4, Blue, 2, Red, 2 - or 4:2:2 - some do 4:4:4 or even 4:4:4:4 (adding black sampling)

The human eye sees contrast best with green light, and the brain draws most of it's information from contrast of black to white (white being all colors)

Monitors experience their highest draw with high amounts of blue or red - why?
Because the human eye doesn't render red and blue as well as green, so more power is required
5w of green will appear brighter than 5w of red or blue - which is why staring at a dim appearing UV diode can damage your eyes - it's VERY bright, just out of human perception.
 
PJ Diaz

PJ Diaz

Well-Known Member
cannabineer said:
And yet my RGB screens on my TV and my phone do a pretty good job. The whiteness of white is very good. Ever look at one with a magnifier? Granted the G is sort of a yellow-green.

I know high-quality photos in magazines use a four-color process. I’m guessing the theatrical units you mention are similar in principle. It makes for a more efficient rendition of perceived color, perhaps ... or a way to add violet to an optimal four-color set.

Im sort of blue-skying here ...
Click to expand...
Yes they do a good job, and your brain is pretty good at compensating for the difference. That said, subtractive color mixing will always give you a wider range of color to mix, albeit at the cost of photon loss.
 
cannabineer

cannabineer

Ursus marijanus
PJ Diaz said:
Yes they do a good job, and your brain is pretty good at compensating for the difference. That said, subtractive color mixing will always give you a wider range of color to mix, albeit at the cost of photon loss.
Click to expand...
I’ll buy that for a dollar
 
Lockedin

Lockedin

Well-Known Member
PJ Diaz said:
Check out this link for the ETC Color Source which is often used in the theatrical lighting industry. You will see that they have two different versions, and it shows which color ranges can be achieved with each version: https://www.etcconnect.com/Products/Lighting-Fixtures/ColorSource-PAR/Deep-Blue.aspx
Click to expand...
Roscoe vs Lee gels - filters placed in front of the lights.
You can change to any color you like with them, but they will knock your ppfd down significantly, but considering that we discuss what happens when we put a sheet of glass in front of a light it might not be a good idea...
 
PJ Diaz

PJ Diaz

Well-Known Member
Lockedin said:
Roscoe vs Lee gels - filters placed in front of the lights.
You can change to any color you like with them, but they will knock your ppfd down significantly, but considering that we discuss what happens when we put a sheet of glass in front of a light it might not be a good idea...
Click to expand...
Yep, that's why video engineers for live concert shoots are having to completely change their color balance style and get their lighting designers on the same page as well. The way colors like deep blue and purples used to hit the cameras with subtractive mixing using gel is WAY different than the additive mixing of LED technology. I've seen lighting designers who don't understand this difference completely mess up live video footage of big acts to a point where the footage is basically unusable.
 
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