Light; marijuana; and lumens

[ganjaluvr]

Hey thanks for posting that on my thread..
I was hoping to get advice/information from people that new the answer..
nevermind.
I was just thinking that maybe there IS a minimum amount of
lumen output you must have for your plant(S) to flower... ya dig?

I could almost swear I read that some where..
reading someones "papers" on growing indoors.
I swear he mentioned or talked about lumens..
and how "the more lumens.. the better" Plant loves light..
the more lumens you have..
the more light you got. The more happy your plant is. Which.. is correct.

However, I am thinking.. ok. The more light the better and happier
a plant you will have.

Fine.

But during flowering.. I'm wondering.. if you gotta have a certain amount of light on your plant for it flower.
If you didn't have enough light "lumens" hitting the plant..
your plant might not ever flower.. or bud. Ya dig?

peace.

I just googled this issue and this is what I found-


Hi folks,

The recent thread on this subject prods me to finally release an old note I did
on it a while back. Re-reading it, it still sounds reasonable, so here it is.
If you have trouble with the figure, try loading it into an editor without a
proportional font.

Lumens, Lux, Foot-candles and other photometric terms are based entirely on how
the average human eye perceives light. Standard observers were defined by
testing many individuals and averaging the results. CRI, Color Temperature and
a host of other common terms all derive from the original work of the
International Committee on Illumination (ICI, or CIE in the French version),
dating back almost 60 years.

Plants don't *have* human vision, so some judgement is required when trying to
use human-sensitive terms to define what our plants need. Sometimes, the exact
opposite of what we want can come from being too slavish to the desire for
"more lumens per Watt." To illustrate this point, look at the relative spectral
sensitivity curves of Figure 1. Plant growth rate is plotted as xxx, while
human eye sensitivity (Photopic, or daylight adapted) is plotted as ooo. The
vertical scales are adjusted so that there is approximately equal area under
each curve.

The dip in the green for plants is evident (they *do* reflect more green away)
and the green growth sensitivity is only about 1/4, compared to what our eye
perceives. In the violet and deep red, the plants have thousands of times more
sensitivity than the human eye. Our visual response in the visible blue and red
is only about 10% what it is in green and yellow.

Any sensible phosphor designer will tailor his lamp to match the human eye
curve, *if* the objective is to maximize lumens per Watt. This means that
phosphors wasting any energy in the blue and red are eliminated. The standard
"cool white" flourescent bulb is a superb example of this kind of engineering
raised to a very high art. The spectrum of cw bulbs closely matches the human
scotopic curve, yielding a lot of lumens/Watt, but only mediocre plant-growth
response. Photos taken under cw flourescents end up with a sickly green tint.

Most of us like to actually look at our plant tanks, so the cheaper
"plant/aquarium" bulbs that have big spikes in the blue and red, with almost no
green may give good growth, but should be only of interest to the pot grower or
other esthetically uninvolved user. A magenta glow is not very pleasing in an
underwater scene. [Spectacular for a tank of neons or cardinals, tho.]

The ideal spectrum for combined visual and growth purposes is a broad-band
source. In fact, an ordinary incandescent bulb, operating at a color
temperature of about 3200K, is nearly perfect. The one small flaw is the large
amount of heat it generates, for it doesn't fall off at wavelengths above
750nm, like the plant curve does. Halides are more efficient, so are even
better, but the heat is still a big problem.

Flourescent tubes are available that give pleasing color rendition, but still
provide better growth efficiency than "cool white." I have grown lush Riccia
fluitans under an 8W cool-white tube, for there is nothing that says plants
have *no* response in the visual region. It just *looks* very bright and
doesn't give the best plant growth.

For about four times the plant growth rate at a slight perceived drop in
brightness, either a daylight or GE Chroma 50 will give pleasant colors and
vigorous plant growth. Phillips Schedule 35 and most tri-phosphors work well,
too. None of these tubes are very expensive. I will reserve my thoughts on the
poorly-designed, unreliable, short-lived specialty tubes, called aquarium
bulbs, sold for four to ten times the price of these suggested, well-engineered
products.

Esthetically, I like a 50-50 combination of daylight and Chroma 50. With only
80W (2 40W tubes) in a shop-light fixture, over a 55G tank, the growth-limiting
factor definitely is CO2, not the light. That's only 1.5 Watts/Gallon, far
below the frequently suggested 2-4 W/G. Even with lower lumens or lumens/Watt
ratings, they are the *growth* equivalent of about 6W of "cool white" tubes.

*figure one can be found on the original website by clicking here*

I sincerely hope this helps clarify how we look at illumination sources for
both our visual stimulation and our plant growth.

My plant curve was derived from textbooks and was taken from data on emersed
plants. It is closer to our reality than the many studies I saw on algal
growth, which lends itself to lab analysis, but doesn't reflect higher-plant
reality very well.

Lumens are for "looking at..." Watts are energy. Neither is the whole answer.
Use good judgement in selecting the best for your tank.

Wright


--

Wright Huntley (40 248-5905 Santa Clara, CA USA huntley at ix_netcom.com




So that is about growth for plants in aquariums, but they are plants none the less. So what Im understanding is that lumens dont have a big role in the growth, but that a HO bulb with the right color spectrum is supreme. And if you are using a small wattage bulb, regardless of the color spectrum, it will not give the plant full growth potential. I could be wrong, Im intrigued now. I always assumed high lumen output with the proper color was the ticket.

 

[strictly seedleSs]

I get what your saying, but Im not sure on a number, like lumen/watts per sq ft or what.

 

[doobnVA]

You can covert the lumen output into a measurement that's more appropriate for plants, but that's about all it's good for.

http://www.sunmastergrowlamps.com/SunmLightandPlants.html

http://www.sankey.ws/plantlumen.html

There's plenty of empirical and anecdotal evidence to show what kinds of bulbs are suitable for growing plants. What determines which one you choose, I guess, is personal preference, and sometimes wives' tales and a bit of voodoo =)

I prefer CFLs and high output floros because they're inexpensive, relatively energy efficient, easy to move, and don't generate a lot of heat and are self-ballasted so I don't need a lot of additional contraptions for powering and cooling them.

 

[doobnVA]

Hey thanks for posting that on my thread..
I was hoping to get advice/information from people that new the answer..
nevermind.
I was just thinking that maybe there IS a minimum amount of
lumen output you must have for your plant(S) to flower... ya dig?

I could almost swear I read that some where..
reading someones "papers" on growing indoors.
I swear he mentioned or talked about lumens..
and how "the more lumens.. the better" Plant loves light..
the more lumens you have..
the more light you got. The more happy your plant is. Which.. is correct.

However, I am thinking.. ok. The more light the better and happier
a plant you will have.

Fine.

But during flowering.. I'm wondering.. if you gotta have a certain amount of light on your plant for it flower.
If you didn't have enough light "lumens" hitting the plant..
your plant might not ever flower.. or bud. Ya dig?

peace.

The plants will flower with very little light, as long as they have a long enough dark period. If you don't have enough light to sustain plant growth, then you wouldn't make it to the flowering stage in the first place =)

More light during flower generally means denser buds, but results may vary.

 

[strictly seedleSs]

This is going to sound like Im an A-hole.

"There's plenty of empirical and anecdotal evidence to show what kinds of bulbs are suitable for growing plants. What determines which one you choose, I guess, is personal preference, and sometimes wives' tales and a bit of voodoo =)"

You were so sound and firm on your opinion, that answer sucks. So personal preference is something you and your plants agreed upon? or is that your personal preference, which would mean your opinion has no proof to back it? Im not sure you know where lumens come into play in this equation.

 

[doobnVA]

One last point about plant grow lights and lumens... LED grow lights don't even have a lumen rating, and if you look at pictures of LED grows the lights aren't "bright" in the visual sense, yet cannabis grows happily under them. They are "dim" to us because they emit almost entirely blue/red light and we see yellow and green light better than blue/red. Plants "see" blue/red light and yellow and green light don't contribute to photosynthesis at all. CFLs and floros are designed to emit light that's visible to humans, and as such they emit a large percentage of light in the green/yellow spectrum even when they're "warm" or "cool".

 

[strictly seedleSs]

Please show me an LED grow with "success". Those things just dont do it. by "success" I mean something even close to an HPS grow.

 

[doobnVA]

This is going to sound like Im an A-hole.

"There's plenty of empirical and anecdotal evidence to show what kinds of bulbs are suitable for growing plants. What determines which one you choose, I guess, is personal preference, and sometimes wives' tales and a bit of voodoo =)"

You were so sound and firm on your opinion, that answer sucks. So personal preference is something you and your plants agreed upon? or is that your personal preference, which would mean your opinion has no proof to back it? Im not sure you know where lumens come into play in this equation.

It's not my opinion that lumens aren't a measurement of light that's usable for photosynthesis. Lumens don't come into the equation at all, because plants don't care what light is visible to humans.

No proof? I've given a string of references, and you even posted one yourself with the conclusion that lumens mean nothing in regards to photosynthesis.

If lumens were an accurate measure of how much light is usable for a plant, then why is the "theoretical maximum" luminous efficacy and highest lumen-per-watt ratio a GREEN spectrum light (which is where humans "see" the best, along with yellow) just happen to be in the spectrum that plants REFLECT??

It's obvious to me that you just want to argue with someone. I've seen a successful grow using LEDs in combination with T5 high output floros. I'll have to apologize for not providing a link, as I saw this in person and not on the internet.

 

[strictly seedleSs]

So you think that 100w of HO 6200k light from a t5, is the same as 100w of 6200k light from an LED? in the post i found on google the author says "Lumens are for "looking at..." Watts are energy. Neither is the whole answer." So if neither are the whole answer each is part of it, there may be more variances (like color spectrum). I just cant see plants growing just as good under a light with minimal lumens.

 

[strictly seedleSs]

so here is the equation to find the optimum light for your room.

Designing a Simple Lighting Layout
Step 1. Determine required irradiance levels in PAR watts/square meter
What is a "good" level of lighting for plant growth? This level depends on a number of factors, including plant type, stage of growing cycle, response to increased light levels, among others. Recommendations offered in technical brochures or articles should be treated as rough guidelines. Within a broad range, plants grow faster with more light; therefore the cost of electrical power versus the benefit of faster or higher growth plays a role.
Since lamp to lamp variations, light depreciation over life, fixture degradation from dirt and line voltage fluctuations all contribute to variability, calculating to three decimal places is unnecessary!
As an example, if a specific technical brochure recommends a PPF PAR irradiance of
400 µmol.m-2.s-1for your plants, the table below shows that you need approximately 85 PAR watts/square meter. The conversion factors between PPF PAR, PAR Watts and lux depend on the light source. For example, a 400 watt HPS lamp has more lumens than a 400 watt metal halide lamp but fewer PAR Watts. Depending on the color temperature of the metal halide lamp, there can be small variations in the conversion factors.
The table below provides a general guideline for metal halide light sources. Conversion factors for HPS sources are similar except that about 10% higher lux or foot-candle levels are required to achieve the same PAR watts/square meter.

Conversion factors for typical metal halide sources
Typical lighting level (can vary widely based on application)PAR Watts/sq. meter watts-m-2
Micro-einsteins or µ-mol-m-2.s-1
Lux lumens- m-2
Foot-candles lumens- ft-2
DarkVariableVariableVariableVariableLow221006,000550Medium4520012,0001100High7535021,0001900Very High13560036,0003300​

For a more technical discussion of the conversion factors among various types of light sources, refer to Langhans and Tibbits, "Plant Growth Chamber Handbook", North Central Regional Research Publication No. 340, Iowa State University (1997). Be aware, that as technology has improved and efficiency of light sources has advanced, the numbers given there are somewhat outdated. Additionally, the article refers to metal halide as one standard light source with a specific spectral output. In reality, metal halide is a generic name, and almost any kind of spectral output can be provided from a custom designed metal halide lamp.
[FONT=Arial, Helvetica, sans-serif]back to top[/FONT]
Step 2. Next calculate (or measure) the area you wish to illuminate in square meters.
Example: For a 12 meter x 6 meter area, this = 72 sq. meters.
Step 3. Area x required PAR watts per square meter = total PAR watts required
Total PAR watts required = 85 PAR watts/sq. meter x 72 sq. meters = 6120 PAR watts
Step 4. Estimate PAR watts required at source (typically 50% higher than in step 3)
If half the light is lost in the fixture, walls, etc. twice as many PAR watts are needed from the source. If 1/3rd of the light is lost (a reasonable estimate for most cases), then 50% more PAR watts are needed from the sources (lamps) than the figure calculated in step (3).
Therefore (1.5) x 6120 =9180 PAR watts.
Step 5. Select a lamp of appropriate wattage (e.g. 400 watt, 1000 watt, etc) and calculate its PAR watt rating.
A 400 watt lamp may have 140 PAR watts, a 1000 watt lamp may have 380 (or 420) PAR watts. Higher wattages mean fewer fixtures and are therefore more economical; however they lead to greater variations in light level. Be alert for the phenomenon of photomapping where plants in areas of higher illumination grow taller than those in darker areas, essentially mapping out the irradiance contour for the area! For purposes of this example, we will select a 1000 watt lamp with 400 PAR watts.
Remember that these lamp ratings refer to initial light values, and all light sources depreciate over the life of the lamp. If you are designing to average or maintained light levels, start at 20% to 30% higher. Be sure to relamp before the depreciation reaches an unacceptable light level.
Step 6. Calculate the total number of lamps (or fixtures) needed
To determine the total number of lamps required, divide the total source PAR watts needed by the PAR watts per lamp 9180/400 =22.95. For this sample calculation, the number is approximately 23 or 24 fixtures.
Step 7. Use a Grid to Design Your Fixture Layout
A square grid or a "staggered" grid may be used to minimize light level variations across the growing area. For example, 24 fixtures can be shown on a 6 x 4 grid or on an 8 x 3 grid. Remember, the higher the ceiling height, the more space is possible between the fixtures. If you find that there will be too many "dark" areas in the regions between fixtures, you may choose a lower wattage lamp and increase the number of fixtures.

I still have issues seeing LED light making good herb. I also read this on the same page.
"Plants receiving insufficient light levels produce smaller, longer (as compared to wide) leaves and have lower overall weight. Plants receiving excessive amounts of light can dry up, develop extra growing points, become bleached through the destruction of chlorophyll, and display other symptoms of excessive stress. Plants are also damaged by excessive heat (infrared) radiation or extreme ultraviolet (UV) radiation. "

So light levels are what you are looking for...you just cant "see" them.

 

[doobnVA]

Can you put up the URL where you found that? It looks like something got lost during the cutnpaste there.

EDIT: nevermind, found it

 

[doobnVA]

I thought I posted a link to that same site earlier in this thread...

Here's a snippet from the previous page on that website http://www.venturelighting.com.au/about/sunmaster/plants_appendix.html

Measuring Light for Humans: Lumens and Lux
First, how do we measure light quantity for humans? The obvious way is based on how bright the source appears and how "well" the eye sees under the light. Since the human eye is particularly sensitive to yellow light, more weight is given to the yellow region of the spectrum and the contributions from blue and red light are largely discounted. This is the basis for rating the total amount of light emitted by a source in lumens.






The output of a 400 watt incandescent bulb is about 25 watts of light, a 400 watt metal halide bulb emits about 140 watts of light. If PAR is considered to correspond more or less to the visible region, then a 400 watt metal halide lamp provides about 140 watts of PAR. A 400 watt HPS lamps has less PAR, typically 120 to 128 watts, but because the light is yellow it is rated at higher lumens (for the human eye).
"Illumination" for plants is measured in PAR watts per square meter. There is no specific name for this unit but it is referred to as "irradiance" and written, for example, as 25 watts/square meter or 25 w/m2.

Clearly, both lumens and lux (or foot-candles) refer specifically to human vision and not to the way plants see light.

 

[masterd]

like i said guys, im pretty sure from my research into mushroom fruiting and actual plant growth the proper measurement is a micro einstein, lumens/lux/foot candle mean the light measured in the green and yellow spectrums, so yeah, lumens mean nothing, and sorry for everyone stealing ur thread dude, plants will go into flower as long as the photo period is right and as long as there a difference between the day/night,

They use lumens to measure light because it is a simple and cheap test and you can compare all lights with this, i think they really should be changed for grow lights because it really doesnt mean all that much, someone without alot of knowledge can be quite confused and buy the wrong product, anyway again, sorry for jacking ur thread dude


EDIT: if anyone wants info on micro einstiens or photosynthetically active radiation (PAR) i just found this
http://home.comcast.net/~cerny/pub/einsteins.html

 

[gammaz]

Lumens are perfectly fine for comparing plant growth lights of the same spectral output.

They use Lumens to measure light because for most purposes, lighting is something that is used to help us humans see things, not becasue it is simple & cheap

 

[masterd]

yeah thats fine if ur comparing a HPS to a HPS but not to compare a LED and a HPS of the same kelvin, and it is alot cheaper to measure lumens compared to using a quantum meter to measure micro einsteins, atleast it was last time i looked at buying a quantum meter....

 

[gammaz]

Im not saying one thing is cheaper than the other, Im sayings its irrelevant, and explaining why Lumens are used, in response to "They use lumens to measure light because it is a simple and cheap test and you can compare all lights with this"

 

[masterd]

yes thats why we measure lights in lumens becaus thats how we see light, thats why im saying it should be changed for any light with the purpose of it being for growing to an accurate measurement of light the plants like, sorry not changed, but incuded,

 

[Purple^stars]

Technically you want the most lumens per watt.

 

[masterd]

Technically you want the most lumens per watt.

technically thats wrong though, the lumen per watt doesnt reflect what alot of different lighting systems produce, there is up to 45% missreading on CFLs growing ability because of lumens, anyway if ur using HID stick to lumens and kelvin and the colour spec. its easier to compare,

 

[gammaz]

If u want a simple way to see the spectrum your light source is putting out, I came across this the other day http://www.cs.cmu.edu/~zhuxj/astro/html/spectrometer.html Dont point it directly at intense light sources, use reflected light off a white surface instead. Unless u like toasted retinas!