How To Compare Grow Lights

[DrPhoton]

Removed for security reasons.

[Campesino]

I appreciate the information and insight, but 5 of the 6 rules are "Don'ts"... So it seems that PPF is what it boils down to.
Are there other factors that you would consider?
Would there be differences if the priority was not efficiency (e.g. distribution, quantity or quality of light)?

[DrPhoton]

Unfurtunately Photon flux is the main metric for accurately quantifying the total output capacity of a light source. I say unfortunately because it is not typically provided by manufacturers as it would show the underwelming performance of most cheap fixtures today. As such they use other quantities and metrics to misguide the consumer in thinking their product is of high quality. Using PPFD maps are good for assessing the distribution uniformity which is always beneficial. However single PPFD on its own is useless, except for knowing the recommended height placement. The quality of light spectrum is really not of big importance, as i have discussed in my other articles, research shows that light quantity is more important than light quality. However making sure there is some amount of blue is beneficial for a better structure for indoor environments. I may add this to the article.

What i would like to add to the response of your question on light quality is about photomorphogenesis. Which is the mediated response of plants to light. Photosynthesis is the main determining factor for energy production, the efficiency of each color spectrum is irrelevant because the quantum yield (photosynthetic efficiency) response is very identical over the photosynthetic bandwidth. With photomorphogenesis, mediated responses from light effects the morphology of plants. I like to think of it as photosynthesis manufactures energy and mediated responses such as photomorphogenesis, thigmomorphogenesis say what is done with that energy. The fact of the matter is that although quality of light can change the morphology of plant, it cannot change the photosynthetic efficiency. It can only indirectly increase the photosynthetic production through capturing more light. Which is why blue is recommended.

That make sense ?

[Campesino]

Yeah...but it raises a question
Seems that you are primarily concerned with photosynthesis and light/energy efficiency. Do you not think that photomorphogenesis is important in directing energy to flowers vs veg growth? I understand that the laws of thermodynamics apply, and total energy limits photosynthetic activity. But we aren't just interested in growing biomass, we are primarily interested in growing flowers. Therefore, I feel like those processes that direct the allocation of growth are really important to consider.

[DrPhoton]

Light and photosynthetic efficiency is what directly drives energy and growth. Although photomorphogenesis has an effect of what is done with that energy, this is really only applicable to plants in vegetation. Once the plant has reached flower induction, photomorphogenesis has no effect on flower morphology as the developement of the flower is already being prioritized, all source energy is being directed to sink locations (flowers). How that energy is used is not defined by the quality of light. Although there is the exception of trichome development, however this is a seperate variable. Which is not fully investigated yet.

From a section of a book i have read on photomorphogesis by hans mohr.

"The characteristics of the flowers (including stamens, pistils, corolla and calyx) are hardly modified by light. A potato plant will form very similar flowers under all circumstances which allow flower formation at all."

The various physiological effects of light mediating photoreceptors have been wonderfully characterised over the decades, none of which are linked to floral morphology.

[redbeard]

U guys are some smart fellers. So with all this being said. What lights do u like . Cobbs,quantum boards, hids

[DrPhoton]

I like ceramic metal halide, although i do have sodium discharge. LED is good if the right product is chosen, eventually LED will be the dominant form of all lighting technologies.

What lighting technology is best for you depends, each provide some unique quality that suits the individual user differently. So theres not exactly one technology that is the best.

Perhaps you might want to look at my grow lighting technologies article.

[MajorTom]

Hey DangerDan; I just noticed this post. Maybe you can help me with my question at the posted link?? Thanks!! MT

[oldjarhead100]

My head hurts and its to early to digest all that lol good write up Danger Dan

[DrPhoton]

Thanks OJ, im taking a break for a while so dont worry no more brain smushing articles ^.^

[Insight]

Thanks for taking the time to introduce the science behind all the lighting hype. I appreciate it.

[DrPhoton]

No problem, thanks.

[Vajipozezo]

Thanks for the detailed clarification. I need to calculate the PPFD for my 1000 watt led grow light. For the 5 meter ceiling mounting, the value is about 500.

But I have a doubt on whether or not we should use monochromatic or full spectrum for grow light purpose. I know it is very controversial. It is because photosynthesis is very sensitive to specific wavelength. And thus some led lighting manufacturer will produce orange or purple lights for grow room. However, other supplier suggests the use of full spectrum...

[oldjarhead100]

I put a 1000 w hps and 8 100 w led light bars with 2 of kinds micro lights for bloom ,I think that covered the spectrum

[Bluto]

Wow. Such a fantastic article. Thank you. So let me see if I have this correct. Ultimately what we should be looking at is um/watt and the higher the value, the better?

[DrPhoton]

Umol per watt is a good indicator of elelectrical efficiency. Which is always important. Photon flux "PPF" is a good indicator of total output capacity.

[Bluto]

Ok. So lets say the light claims to be a 400 watt hps equivalent. Pulls 214 watts from the wall. Total ppf is 470 Umols/sec, efficiency ppf/watt is 2.2 umols/watt and total ppfd is 430 umols/m2/sec. That's the information we should be looking at? Also, with total ppf @470 and ppfd @ 430, those are the numbers that back up the claim it's a 400 watt hps equivalent?

And then there's color temperature. For a full spectrum light, veg to flower 3500 seems to be average, I think, but if you go lower its better for flower and higher is better for veg, yes?

[DrPhoton]

Exactly. 👍

[Bluto]

@DANGERDAN
Sweet. Thank you fine sir!

[DrPhoton]

Improved readability and added further information.

[freddyyola]

whats a good or great cmh or led light for 200-300 usd or should i just get an hps 1000 watt to start out with cause for my first grow im aiming for yield over electricity cost and if i can control the heat in the summer idc what light it is. pretty much saying i dont want anything fancy i cant afford it yet! what would you buy if it was your first light and you had 200-300 to spend on it

[DrPhoton]

You will not be able to get a LED fixture at that price point that competes with gas discharges efficiency and performance. If you are looking for maximum yield, you want a light source that accomodates your grow space with the maximum photon flux levels for that area. For example a 4x4 should not have anything more than 600w HPS. Where as a 5x5 should not have more than a 1000wSE HPS. Double ended fixtures should not be used for spaces less than 5x5.

CMH can compete with sodium discharge with efficiency, but they cannot compare in total photon flux. A 615w CMH can satisfy up to 4x4. If you can afford a 615 CMH, this would be the best choice as you can use the same fixture for the entire grow. Where as with sodium discharge, you need to use halide discharge together. Which is a downside compared to ceramic metal halide.

[freddyyola]

and is used hid's or led's really an option?

[DrPhoton]

Used gas discharge basically means just the hood/reflector, as you would ideally just buy a new bulb for it. So yes, you can buy a second hand reflector, but you ideally want to replace the bulb as previously said. Second hand LED is likely not in the equation, as you would still need more budget to aquire a fixture to compare with gas discharge.

[freddyyola]

so when you are looking at leds the wattage they show like a 1200 watt led really kinda means 1200 watt hps equivalent i know its not exact cause thats how they make there money but is it close?

[DrPhoton]

It can mean a few things. Such as the total wattage value of all the diodes combined, which is a pointless metric. Or an equivalent gas discharge value. Which is highly unreliable. Or the actual power consumption. So you have to read the products description carefully because manufacturers will misrepresent what thr product actually is to provide the appearance of a superior product.

[freddyyola]

https://www.amazon.com/MORSEN-Reflec...ustomerReviews can u look at this light and let me know if the price is really to good to be true and if its under powered would doubling up on them and such a low cost be better than spending 250 -300 on another different light? thanks in advance hope you mind the back to back posts

[freddyyola]

oh and thanks for the help guys his forum has helped me alot!

[DrPhoton]

LED products from companies such as california lightworks, spectrum king, fluence, nextlight, and black dog provide comparable performance to sodium discharge, but require a substantial investment that take years to recover the initial costs. So they are not cheap.

Rapid LED offer about the most simplest solution to purchasing and assembling DIY fixtures. However you have to be able to understand some basic principles in electronics or follow their insutructions carefully, there is still some DIY involved. There are a couple of people here who have made these fixtures with good success.

[freddyyola]

ive heard of rapid led and i think i can figure it out ima give it another quick research / lookover but right now i dont think its the best choice for me in my situation since im finding such good deals used hps set ups im thinking ill get started with hps and then upgrade or add leds as i go to get more sprectrum and watts without adding much more heat.. the only thing that turned me away from rapid led is if its diy it should b e less expensive but i didnt see the price difference being worth it..