UV Light and Terpenoids

[spurr]

UV-c isn't high in the mountains, it's really well filtered out by gasses in the atmosphere. There can be some UV-b at the very high elevations, but it's not high.

The higher you go into the mountains the more UV you will get.The air is thinner.Why do you think that people like e.g. Nepalese has a darker skin. Never seen a Tibetan with a white skin.
UV-index in regions like Oaxacan is > 10 at 1.00 pm during the summer.

You can't lump all UV into one claim like above, UV-c is very damaging to humans and animals and microbes too. It's true the the higher the elevation the more UV-b you will get, but, even at 10,000 ft, you will have very little UV-c.

The UV-index is comprised of UV-b and UV-a, very little (near nil) UV-c makes up the index.

The reason Nepalese people have darker skin is likely not directly correlated to UV levels; otherwise they would be darker than Africans who live at far lower elevations, but that isn't so.

Those gasses you talking about is badly affected by environmental pollution.

The gases I am writing about stay in the stratosphere (for the most past, unless man made, then the make their way up there) and they block UV-b and UV-c (more so the latter). If you are referring to ozone depletion that is not a major issues any longer due to reduced usage of CFCs by the major industrialized nations. Besdies, IIRC ozone is created as UV-b enters the upper stratosphere.

 

[spurr]

So lets concentrate on why you think is not practical because the low accuracy. If I thought you were not understanding my point was because the insistence on your arguments about why inverse square law is not valid. When I never talked about inverse square law at all. It refer to a virtual condition, useful to explain some things to people starting to study lighting, but almost never found in reality. As most, is near and can be used as simplified way of calculating very special situations. Its not the rule at all, and its not used by lighting designers.

I have criticized many times how people misuse square law too, and more yet, that they actually dont understand it.

I agree completely about the inverse square law, it's almost like a default answer for most people.

I assumed you were trying to use the inverse square law by your description of your methods, sorry for making a wrong assumption. You had not described what equations/methods you employed to use radiance (non-incident light, not by density) to find irradiance (incident light, by density); so I wrongly assumed you were trying to use inverse square law.

Could you elaborate on what software you do use? You now have me intrigued that I was wrong about use using inverse square law.

In lighting, radiance is the cause and irradiance, the effect (or consequence). Platon (do you write so?) analogy of the cove is very useful to illustrate what I mean. The fire at the start of the cove is the light source. Its proyected to the end, in deep, of the cove. People passing between the fire and the cove proyects a shadow on the deep wall.

When you measure irradiance, you are measuring those proyected shadow. Its almost impossible to know from that the exact nature of the objects that passes behind the fire, because shadow are deformed at the walls irregularities (and more reasons. I dont want to go too far with the analogy, just illustrate the concept).

On the other hand, if you are at the fire, you see directly objects passing behind the fire. When knowing those object is important, looking at the fire is way more useful and accurate. But more yet, it you know how is the bottom wall and have characterized the light source, you can get a good generalized idea of how shadow will proyect on it.

I am a bit confused by your analogy. If "fire" is the light source (e.g., lamp) and the "proveted (sic; i.e., projected) shadow" is the area of incident light (e.g., canopy by density, ex., meter^2), what are the "objects that [pass] behind the fire"? Do you mean intra-and-lower canopy (i.e., whole canopy)?

Correct me if I am wrong: you are claiming the shadow (incident light) is effected ("deformed") by reflection from walls (e.g., walls of a grow room), thus you can't use incident light (i.e., irradiance) to measure light intra-and-lower canopy?

Further, you seem to be claiming that by looking at radiance (at lamp), and knowing distance to canopy and canopy dimensions, you can draw a generalized idea about the irradiance at canopy? If so, that sounds very much like inverse square law (ISL) which is why I wrongly assumed you were using ISL.

It's true you can use radiance to get a "good generalized idea" of irradiance if you know distance to canopy and canopy dimension, but that is not as accurate as measuring irradiance directly.

Both radiance and irradiance are good to know, but of the two, the latter is far more useful and accurate in terms of incident light. When you wrote about light intracanopy a few posts ago I mentioned that each whole canopy is different and each grow room is different (e.g., reflective walls, glass under HID, humidity, etc.). That is why I wrote using irradiance (e.g., as PPFD) is the better method (in my opinion) becuase a grower can measure it at top of canopy, intracanopy and lower canopy for proven data. Then a grower can adjust LAI (leaf area index) and LDI (leaf destiny index) of the canopy, and a grower can use a "closed canopy" like SCROG or a "open canopy" like SOG if they want more or less light intracanopy depending upon the irradiance measurements and growing style.

There are far too many variables with canopy structure, leaf angle, gasses (ex., water vapor), reflective walls, "sunfleck", etc., to use radiant light with math, to find very accurate irradiance figures intra and lower canopy. Using radiance to find irradiance at (top) canopy is more accurate than using radiance to find irradiance intra and lower canopy. However, measuring irradiance directly is better than using radiance and math, for very accurate data.

I think we are back to what I wrote before, respectfully, we will have to "agree to disagree" on the 'best' method to quantify incident light for canopy, and intra to lower canopy too.

Scaling radiance by irradiance measurement is not possible. No matter you take 144 measurements on a 1 m2 area. You wont get any accurate figure that way. You would need to take way more measurements to be able to say with some confidence than scaled up radiance figure obtained is below 15% error.

What do you mean by "scaling radiance by irradiance"? No one is using irradiance to find radiance. I/we use incident light measurements to find irradiance. Using a quantum sensor to find irradiance is by far the most accurate method to measure incident light at canopy.

Using 144 measurements with a quantum sensor over a meter^2 is a quite accurate method to find PPFD; more accurate would be more measurements, say one every inch. But one measurement every three inch is still quite accurate to find PPFD, or to find irradiance over canopy sizes other than meter^2, e.g., foot^2, 2 foot^2, etc.

It's true that radiance should be considered before buying a light source, e.g., I would want to use a 1,000w HID for high radiance to know I will be able to get high irradiance at reasonable distance to canopy; but the radiance doesn't tell me (accurately) irradiance.

If you look at how light is usually distributed, you realize is nothing homogeneous. There are noticeable differences at 1". More yet, you are using an hemispherical detector, very useful to avoid orientation of detector affects too much measurement, but very bad for integrating measurement on a coherent way. Bad accuracy and unpractical.

A good cosine corrected quantum sensor measures incident light at ~80 degree angle from level surface, which is pretty good. I agree light is not homogeneous, that is why using a quantum sensor to measure actual indict light is better than using radiance and math; the former is real-world measurements. Measuring incident light every inch is better than every 3 inches, but measuring by every 3 inches is quite accurate; measuring every inch would take a long time.

You can not know from irradiance measurement the absolute light actually falling on a given area.

Yes you can, more so than using radiance to find incident light. That is the whole reason we measure incident light with a quantum sensor. Because it measures actual light and accounts for factors that affect photons as they travel from light source to destination because quantum senors only measures photons that are incident upon the area of interest.

But knowing the absolute radiance alone, without scaling it to irradiance is yet a very useful data, that help a lot putting in perspective irradiance measurements. With both, accurate simulation, and irradiance measurements giving the most exact info of the grow area, and correcting simulations for the higher accuracy, you have a way better idea of how is the light in the grow, and actually, way better figures in which base your conclusions.

100% agree! That said, of the two, irradiance is more important to measure than radiance, in my opinion.

If you dont use filters or diffuser over the LED array, actually you can treat them as many indicidual point sources, making simulations easy and very accurate.

AFAIK that depends upon the angle or radiance, i.e., a wide angle LED is less of a point source than narrow angle led. And once many LEDs are in a panel, it's less of a point source. Please correct me if I am wrong.

Many studies are flawed because they state max irradiance (or simply,irradiance at the center of the area) obtained on the experimental chamber at the given distance of the lamp, but irradiance along the rest of the chamber in many cases (as experiment was designed) is very different.

Some studies are flawed in that, I agree 100%, as is the method of using of spectroradiometers to find uW/m^2 unless the sensor is used to measure uW over a meter^2.

That is why I write to find PAR range microMole irradiance over an area, ex., meter^2 (i.e. PPFD), we need to (at least) measure every 3" over the whole area of interest, then average all datum to find a single figure of irradiance over X area. Graphing the irradiance at every 3" (or 1") measurement allows for better understanding of heterogeneity of irradiance (i.e., peaks at various areas of light footprint).

Im glad to find someone able to discuss these topics in deep and make me think about the flaws on my procedures. Feedback and constructive criticism is the way of progress.

Ditto, I have learned a few things from our discussion, thank you very much

PD: Send me a PM,no problem about using email to send documents

Will do, however, I think I may be able to download that file tomorrow. I will try and if I fail I will PM you.

Best regards, spurr

 

[spurr]

Yes, I based my sheet on the work of Ivo Busko. I believe at the GC thread I explained the process of building it. Although it started for the work of Ivo, and the full concept of the sheet is of him, I quickly realized his method of calculating depended a lot of the SPD introduced.

Yup, that is where his method is flawed, etc.

First, although thought to be used with relative SPDs, as I replied his procedure, I found only works for SPDs representing a fixed lm figure, and its not the rule. I modified the calculation procedure to avoid this. Result is absolutely independent of SPD scale of its match with a lm figure. Only worth the relative values, if they are good, and thats is granted with a good calibrated spectrometer as used by lighting companies.

Great, good to know. I for one like your spreadsheet very much, I have made use of it before, and I plan to make very heavy use of it in the future with my spectroradiometer and quantum sensors, etc.

Second, I developed some way of digitalizing graphs in a way that strongly minimize human error translating figures. Always remain a margin of error due resolution of the graph, of course, but its kept at a enough low figure to end results are accurate. Not a problem at all for spectral analysis alone, and minimal error added when using lamp wattage and lm data.

Last I checked your directions you where using MSPaint, are you still using that program? FWIW, often times if you ask the lamp manufacturer for spectroradiometer raw data, what they used to make SPD, and they will send it to you. That way you don't need to digitize the SPD because you have the actual data you can simply input into your spreadsheet. That seems to be the most accurate method I have found to use your spreadsheet (instead of digitizing SPDs).

As I believe you know, I checked results with reliable manufacturers data obtained with high end NIST traceable light measuring systems and results are very close on all figures, for many different lamps. Almost always below 5% difference, and mostly below 3%. Funny thing is my results was always slightly lower than published, and yesterday I found why, the coefficient applied to convert optical watts to photons was 2.9% higher than it should. Meaning that if now I check results, they are going to be surprisingly close to manufacturer data. A margin error way lower than I dreamed this method can provide.

Good to know, thanks.

I developed it for comparing bulbs for growing when all a grower has is his computer. Its excellent for it.

Yes, I agree.

Unfortunately, I dont trust on specs of many companies.

That is what I found too, and it's a real shame.

If you dont mind, or have the resources for such equipment, all I can say is great for you and for us if you share your findings. I would love to see an action spectrum of photosynthesis for cannabis, specially at Photosynthesis saturating levels. You would need equipment to measure Co2/O2 fluxes too, I think.

The Pn/Chl fluorescence chamber measures Co2/o2 fluxes as well

I dream with an equipment like all that, really. With it, you can study whatever you want to and get results and conclusions beyond what I believe any grower has ever imaginate. I hope you can join all that and perform such things. Big $$

All the best

Thanks, the integrating sphere needs to be used with their spectroradiomter, the combo is ~$45,000 USD. I should be able to buy it next year sometime. I will get the Chl fluoroemeter this year and the Pn/Chl fluorometer chamber this year, or next. I was planning on asking you to work with me once I have my tools, I think you and I could get some great things done working together (even though we live in different countries).

 

[spurr]

This paper doesn't go to UV and terpeniod production specifically, but it does go to refuting any reference to UV and plant interaction as being "theoretical."

A UV-B-Specific Signaling Component Orchestrates Plant UV Protection
http://www.pnas.org/content/102/50/18225.full

This one is a summary of studies from "Plant Physiology" by Carlos Ballare.

Stress Under the Sun: Spotlight on UV-B Responses
http://www.plantphysiol.org/cgi/content/full/132/4/1725

Great finds, thanks!

 

[spurr]

@ all,

Here is a good study looking at UV-a and UV-b irradiance of various UV-b lamps commonly used by cannabis growers (i.e., small wattage fluorescent lamps like ReptiSun). The measurements are at 30 cm (~11") and show just how little UV-b is attained from those lamps:

"UV-lamps for terrariums: Their spectral characteristics and efficiency in promoting vitamin D3 synthesis by UVB irradiation"
Jukka Lindergren
Herpetomania, vol. 3, no. 4 (2004)

 

[knna]

Ill put all the question in perspective, spurr, so you can understand better my reasoning.

Plants total photosynthesis is tightly coupled to total photons incident on leaves (total of plant). This is somewhat the axiom that support most botanical research.

It is very different the approach to this depending of lighting used on the experiment. Sunlight is delivered on gigantic amounts from very far (1UA). Only way of calculating total amount of photons reaching a plant is by measuring irradiance and them making some calculations to approximate the total amount of photons. This calculation is always very approximative (more or less depending of how many measurements are taken). For typical studies measuring irradiance at top canopy, margin error is very noticeable, but botanist thinks that as anyway sunlight is inherently variable, that way is good enough and almost the best they can get for studies under sunlight.

Sunlight varies along the course of day and no day is exactly the same than other. Botanists works on the assumption that average along a period is somewhat linked to the single measurement. Lately has been developed data loggers that can track sunlight variation with time, but usually only on few point of a large field. Very good to track conditions on such field and to compare with other studies with similar measurements, but anyway it only allows to make approximative calculations of total photons falling on plants.

Which allows to make such calculations with decent accuracy is the fact Sun is so far that usually a measurement on one point gives a figure valid for almost all the field (only local conditions, as clouding, etc, could affect it).

On the other hand, such homogeneity on light distribution is not present when artificial lighting is used. Thus in order to make such approximative calculation using irradiance data, it would be required to perform a lot of measurements each time. And still so, error margin increases noticeably.

But if known output lamps are used, total photons delivered to plants can be known way accurately. Very easy, and more yet, with higher accuracy or at least, similar than when doing a lot of irradiance measurements. Total amount of photons is tightly linked to total photosynthesis, so knowing it this way, with an small error margin (because little calculations are required) is very useful as a baking data for all other data obtained.

Its true that local photosynthesis rate (on a leaf) depends directly of irradiance. So any study for a single leaf must use just irradiance. But when studying full plant photosynthesis,total amount of photons delivered is the key data, and knowing lamp's radiance is the best way to know it.

Of course, there is a lot of things to study that need to know irradiance, and its a must to have track of it. As I said other times, each figure is useful on their own context and for its own applications. Its not to choose if using one or the other, but we need to use both when using artificial lighting.

Other very different question is how to know irradiance from radiance data. Its is possible to know it with a no excessive margin error, but it only usefulness is when designing a given lighting or experimental chamber, in order to decide what lamps, what power and what optics are required. Once built and running, there is no sense on working on calculated figures when you can measure them directly.

If you remember, this topic raised because of my calculation of the watts of a type of lamp required to use to obtain a given amount of UVB. On average irradiance, and not in true, actual one, which depends of the optics used. Its just useful to calculate aprox which you will need to use. Nothing else.

For this, Ive used Dialux software. There is way better and higher accuracy ray tracing software available, but this one is free on pages of lighting companies, and although uses its own format (so you cant import directly lamps files on IES format), main lighting manufactures has their catalogs ready to use with it, and its easy to use. For LED lighting, Osram has available the files for Golden Dragons, so its possible to calculate vary accurately results using them before installing.

This type of software uses a file of the lamp/bulb very well characterized, with a plot of the light intensity (cd) on each direction on space (a plot for each degree of the full 360º). With that info, and the reflectivity/absortion of each surface on the area, program calculates lighting figures on any point/plane of the area.

Ive seen some studies devoted to develop ray tracing software specific for plant's analysis, but I dont know if there is any actually already working. These calculations are very time consuming, and for me is enough to get a good approximation in order to design a grow area/experimental chamber, and later tune it in situ once built. I dont see the point of getting a very high accuracy on this, its just a tool to design lighting, thats all.

 

[knna]

Spur, I see you still think that is possible to integrate irradiance measurements to obtain the absolute amount of light falling on a given volume.

I strongly disagree this. Its a method that is you perform very carefully and with enough measurements, could be used with a decent rate of error. But apart of time consuming, its easy to get a result very far from reality. Depending of sensor used, light homogeneity, area geometry and way of measuring, margin error may be huge.

As we seem to disagree on this, all I can say to you is do it and check result with actual radiance data. Some things there is only one way to know them, in the practice.

Last I checked your directions you where using MSPaint, are you still using that program? FWIW, often times if you ask the lamp manufacturer for spectroradiometer raw data, what they used to make SPD, and they will send it to you. That way you don't need to digitize the SPD because you have the actual data you can simply input into your spreadsheet. That seems to be the most accurate method I have found to use your spreadsheet (instead of digitizing SPDs).

You can use any program able to resize graph to a given width of pixels and that tells you the pixel number when you put mouse on it. As almost all people has MSpaint in their computer, I suggest it.

I rarely use it, just when analyzing new developed lamps to have an idea. Usually I use directly measurements with my spectrometer, with a sheet adapted to it (bands of aprox 0.35nm instead of 1nm).

The Pn/Chl fluorescence chamber measures Co2/o2 fluxes as well

That is great! With fluorimetry and CO2/o2 fluxes is possible to track PSII activation state and check with gas evolution. I believe that it would allows to get a quick very accurate idea not only of individual waveband's efficacy, but of different wavebands together, without the need of performing whole grows under it

Now I understand your comment of the signal:noise of the spectroradiometer. For fluorometry, you need a very good one

Thanks, the integrating sphere needs to be used with their spectroradiomter, the combo is ~$45,000 USD. I should be able to buy it next year sometime. I will get the Chl fluoroemeter this year and the Pn/Chl fluorometer chamber this year, or next. I was planning on asking you to work with me once I have my tools, I think you and I could get some great things done working together (even though we live in different countries).

I would love to be able to participate on it, still on the distance. At least I always can send you a LED lamp with a very well known output and adjustable to exact needs, so you can work with narrow wavebands. I gladly offer any help, opinions or ideas. BTW, air travel is cheap lately

 

[sm0k4]

I have gotten through a bunch of the articles posted, Spurr, but I have some questions since the terminology gets the best of me for a lot of the chemistry related info.

From what I've been reading, it seems like UV-B is taken differently by all plants. Some can defend against it and some can't. Do you surmise that it is a defense reaction and Cannabis Sativa uses THC and resin production as a defense or way to absorb the radiation so it does not die? This might attribute to the effectiveness of shorter UV exposure times.

I'm interested in this topic and will continue reading, but this seems to be a similar conclusion from those reports. Also, some were done on 9 month old plants. Perhaps they could withstand it more due to age?

Definitely an interesting topic.

 

[B. Friendly]

sayin Dif LIGHTS AND SPECTRUMS will not effect colour, flavour, smell, taste, even the touch of your nugs, is like saying ah no dif as to what you put in your crop for FERTILIZERS.

that said. what goes in has a 100% effect as to what comes out.

how do i know this, easy, grown chem and grown organic, Used HPS and used MH, also used reptile lights and even energy effecient buds.

shit got pk goin now. the bud closest to the "energy effecient bulb" has purple hairs comin out, never seen that before.

anybody that trash talks this post does not grow mj. so that said, I don't care for your opinion, simply stating facts
will shoot pics manana
adios amigos

 

[B. Friendly]

bud that's closest to energy saving light.

 

[B. Friendly]

same plant grown under MH, hope the pics do some justice

 

[spurr]

Hey knna,

Ill put all the question in perspective, spurr, so you can understand better my reasoning.

Plants total photosynthesis is tightly coupled to total photons incident on leaves (total of plant). This is somewhat the axiom that support most botanical research.

Yup, that is what I thought you meant by "shadows", re whole canopy incident photons.

It is very different the approach to this depending of lighting used on the experiment. Sunlight is delivered on gigantic amounts from very far (1UA). Only way of calculating total amount of photons reaching a plant is by measuring irradiance and them making some calculations to approximate the total amount of photons. This calculation is always very approximative (more or less depending of how many measurements are taken). For typical studies measuring irradiance at top canopy, margin error is very noticeable, but botanist thinks that as anyway sunlight is inherently variable, that way is good enough and almost the best they can get for studies under sunlight.

Yup, and they also tend to not take many measurements over an area, because on a cloudless day photons striking all areas within a meter^2 will be fairly similar in quantity. That is a reason why many studies looking at PPFD under artificial light are flawed, often they too only use one measurement and assume all other areas in the meter^2 under a lamp in a reflector, or LED array, has the same quantity of photons, which is not correct.

Sunlight varies along the course of day and no day is exactly the same than other. Botanists works on the assumption that average along a period is somewhat linked to the single measurement. Lately has been developed data loggers that can track sunlight variation with time, but usually only on few point of a large field. Very good to track conditions on such field and to compare with other studies with similar measurements, but anyway it only allows to make approximative calculations of total photons falling on plants.

Yes, it's much better to use DLI (Daily Light Integral) than PPFD when measuring photons in terms of what a plant gets all day. DLI is the sum of PPFD over the day as mol/m^2/day. Under artificial light the PPFD all day is the same, thus using DLI is good. But under the sun, PPFD changes each day and throughout each day (i.e., PPFD is highest around noon, there is a bell-curve of PPFD under sun), so using 3-day DLI is good, i.e., mol/m^2/3-day.

DLI can also be calculated for any area using umol/second. I for one kind of dislike PPFD becuase by definition it is over a meter^2, but for indoor gardens, the canopy is often larger or smaller than a meter^2. That is why I like simply using irradiance as umol/second/X-area.

Which allows to make such calculations with decent accuracy is the fact Sun is so far that usually a measurement on one point gives a figure valid for almost all the field (only local conditions, as clouding, etc, could affect it).

Yup, that is why measurements using a quantum sensor or spectradiometer are only taken a one point, and assumed to be correct for the whole meter^2.

On the other hand, such homogeneity on light distribution is not present when artificial lighting is used. Thus in order to make such approximative calculation using irradiance data, it would be required to perform a lot of measurements each time. And still so, error margin increases noticeably.

Yes, like I wrote above. That said, if one takes enough measurements over a m^2 there is a very small error margin. Ex., as I measure PPFD, I take measurements every 3" over the whole meter^2 for a total of 144 measurements. Then I find the average of those measurements for the PPFD of the meter^2. The quantum sensor I use is about an 1" in diameter, so the final PPFD is accurate after taking measurements every 3". The assumption is, umol/second in the unmeasured 1-2", for every 3", is very close to the umol/second measurement for the 3"; with a good reflector that is a sound assumption. I have tested taking measurements about every 1" and the PPFD was very close to PPFD from measurements every 3".

But if known output lamps are used, total photons delivered to plants can be known way accurately. Very easy, and more yet, with higher accuracy or at least, similar than when doing a lot of irradiance measurements. Total amount of photons is tightly linked to total photosynthesis, so knowing it this way, with an small error margin (because little calculations are required) is very useful as a baking data for all other data obtained.

Yup, except when the lamp is in the reflector. The reason being irradiance is much different for an area under a lamp not in a reflector verses an area under a lamp in a reflector. That is the main reason I prefer measuring irradiance instead of trying to use models. Using a quantum senor we account for how photons travel once reflected from the reflector; as well as accounting for "re-strike", the act of photons bouncing off the reflector and hitting the lamp, which heats up the lamp and reduces irradiance (as well as changing the SPD a bit).

Its true that local photosynthesis rate (on a leaf) depends directly of irradiance. So any study for a single leaf must use just irradiance. But when studying full plant photosynthesis,total amount of photons delivered is the key data, and knowing lamp's radiance is the best way to know it.

I disagree a little, IMO the best way to find potential whole plant photosynthesis by means of total irradiance for the whole canopy is to measure irradiance at canopy, intracanopy and lower canopy. I.e., "transmitted photosynthetic photon flux density" (PPFDt) and "intercepted PPFD" (PPFDin); the latter being the difference between "incident PPFD" (PPFDi) and PPFDt. The reason I feel this way is that Leaf Area Index, openness of caonpy, leaf reflectance, leaf absorbance and leaf transmittance, as well as chamber/room reflectance and usage of a reflector, etc., affects whole canopy irradiance and I assume those factors would be hard to accurately model.

The main reason to measure PPFDt is blue and red photons have very-low rates of transmittance through leaves, green has a low-medium rate of transmittance (and a medium rate of reflectance downward into canopy), and far-red has high rate of transmittance. I assume that means we would need to account for light quality (spectrum) intra and lower canopy, if using a math model from radiance, and not measuring with a quantum sensor. The other main reason I prefer using a quantum sensor to find PPFDin is it accounts for reflection and lack of reflection, off of leaves, walls, floor, etc.

Along with leaf transmittance of photons and leaf/chamber/room reflectance of photons, LAI (Leaf Area Index) is a major factor that affects PPFDt and PPFDin. The openness of the canopy is also a major factor affecting PPFDt and PPFDin, e.g., a SCROG canopy is a "closed-canopy" thus it has lower irradiance intra and lower canopy verses an open-canopy.

see:

"CROP LOAD EFFECTS ON LEAF AREA EVOLUTION AND LIGHT INTERCEPTION IN 'MONTEPULCIANO' GRAPEVINES (VITIS VINIFERA L.) TRAINED TO 'TENDONE' SYSTEM" link

"Crop productivity in relation to interception of photosynthetically active radiation" link
​

Of course, there is a lot of things to study that need to know irradiance, and its a must to have track of it. As I said other times, each figure is useful on their own context and for its own applications. Its not to choose if using one or the other, but we need to use both when using artificial lighting.

I agree 100% that using both irradiance measurements and modeling from radiance is the best way to go for the most complete data sets. I however feel if a person had to choose only one, using irradiance measurements gives more accurate real-world data for incident photons over the whole canopy.

If you remember, this topic raised because of my calculation of the watts of a type of lamp required to use to obtain a given amount of UVB. On average irradiance, and not in true, actual one, which depends of the optics used. Its just useful to calculate aprox which you will need to use. Nothing else.

Good point.

For this, Ive used Dialux software. There is way better and higher accuracy ray tracing software available, but this one is free on pages of lighting companies, and although uses its own format (so you cant import directly lamps files on IES format), main lighting manufactures has their catalogs ready to use with it, and its easy to use. For LED lighting, Osram has available the files for Golden Dragons, so its possible to calculate vary accurately results using them before installing.

What other software do you think is "way better"? I ask because I could probably buy the software and send you a copy, that is, if the software is under a few thousand USD

This type of software uses a file of the lamp/bulb very well characterized, with a plot of the light intensity (cd) on each direction on space (a plot for each degree of the full 360º). With that info, and the reflectivity/absortion of each surface on the area, program calculates lighting figures on any point/plane of the area.

That is my main issue with such software, it uses 360 degrees, but a lamp in a reflector does not direct light 360 degrees. And the irradiance of a lamp in a reflector is much higher than the irradiance of the same lamp not in a reflector.

Ive seen some studies devoted to develop ray tracing software specific for plant's analysis, but I dont know if there is any actually already working. These calculations are very time consuming, and for me is enough to get a good approximation in order to design a grow area/experimental chamber, and later tune it in situ once built. I dont see the point of getting a very high accuracy on this, its just a tool to design lighting, thats all.

Yea, I agree.

Thanks, it's always a pleasure to read your thoughts and knowledge. Your posts always make me re-think my position, and have taught me things too.

 

[spurr]

Hey again knna,

Spur, I see you still think that is possible to integrate irradiance measurements to obtain the absolute amount of light falling on a given volume.

I strongly disagree this. Its a method that is you perform very carefully and with enough measurements, could be used with a decent rate of error. But apart of time consuming, its easy to get a result very far from reality. Depending of sensor used, light homogeneity, area geometry and way of measuring, margin error may be huge.

I do agree I should not have used the term "absolute", I should have written "very near absolute", i.e., the total irradiance as PPFD and as intercepted PPFD (PPFDin), over the whole canopy with a small error margin.

Properly measuring irradiance over the 'canopy' (area) for a small error margin is much less time consuming than properly measuring irradiance over the 'whole canopy' (volume).

The Pn/Chl fluorescence chamber measures Co2/o2 fluxes as well

That is great! With fluorimetry and CO2/o2 fluxes is possible to track PSII activation state and check with gas evolution. I believe that it would allows to get a quick very accurate idea not only of individual waveband's efficacy, but of different wavebands together, without the need of performing whole grows under it

Yup, along with measuring E, Gs, etc. Neat stuff for sure

I would love to be able to participate on it, still on the distance. At least I always can send you a LED lamp with a very well known output and adjustable to exact needs, so you can work with narrow wavebands. I gladly offer any help, opinions or ideas. BTW, air travel is cheap lately

That sounds great, I will take you up on the offer for LED arrays, for sure! I would love to order a few from you, and of course make it worth your time to build them and send them to me. I have made some notes on LED arrays I would like to have in terms of light quality, as long as they are capable of providing high irradiance, up to 1,500 umol/sec/area; an area of about foot^2 or two feet^2, or even meter^2. I would very much like to work with you, even if from Spain, you know a lot, and you know things I do not, so I think we would make a great team.

I have always wanted to visit Spain, I have even thought about moving there before due to the climate, sun, cannabis laws, women, beaches, wine, etc. If you are serious, I would love to come to Spain sometime near the end of this year, or the start of next year, and meet up with you. I could bring some of my equipment (once I buy them) like Pn/Chl fluorescence chamber, integrating sphere/spectradiometer (to make ASP for cannabis), etc., and we could work there for a couple of weeks.

 

[spurr]

I have gotten through a bunch of the articles posted, Spurr, but I have some questions since the terminology gets the best of me for a lot of the chemistry related info.

From what I've been reading, it seems like UV-B is taken differently by all plants. Some can defend against it and some can't. Do you surmise that it is a defense reaction and Cannabis Sativa uses THC and resin production as a defense or way to absorb the radiation so it does not die? This might attribute to the effectiveness of shorter UV exposure times.

I am not sure, I know many flavonoids are UV-b screening agents, they proect the plant from UV-b, but I do not know if THC is also a screening agent. It might be that increased THC production from UV-b could simply be a reaction (e.g., greater conversion of CBG into THC verses other cannabionoids) without a definite purpose; or it could be that THC is a UV-b screening agent (e.g., greater conversion of CBG into THC verses other cannabionoids). The paper by David Pate, titled something like "evolutionary impacts of UV-b on cannabis" I posted, has some insight.

IIRC the conjecture filled article "marijuana optics" (link) proposed glandular trichomes and possibly some cannabinoids screen UV-b. That article makes the incorrect claim that THC is derived from CBD, i.e., CBD is a THC precursor. Current scientific evidence finds that THC and CBD both come from the precursor CBG, and CBC also comes from CBG.

I'm interested in this topic and will continue reading, but this seems to be a similar conclusion from those reports. Also, some were done on 9 month old plants. Perhaps they could withstand it more due to age?

Definitely an interesting topic.

I do not think age is a factor, once plants are no longer juvenile. I supply UV-b during veg and all of flowering.

 

[hades]

Hi again Spurr,

Haven't had a chance to catch up, but plan on sitting down tonight. Just got a space, need to convert it into lab quality grow environment.

They listened to our petition over at the MNS camp, and you can now access any content over an HTTPS connection. They do use a self-signed certificate, which has benefits and drawbacks. You probably know this, but the first time you use it your browser will wig. It is safe to confirm and store the exception the first time you visit using HTTPS.

Probably going to start a thread on this topic soon over there.

Don't mean to hi-jack the thread, but I still can't PM and I had no other method of passing on the news...

Keep up the good work, I know I have a lot to read in many threads.

 

[spurr]

hey,

Good to hear they now have HTTPS, I will start posting there more, now they have HTTPS. I'm glad we were able to influence the use of HTTPS

I have been thinking about ways to increase the footprint of UV-b mercury vapor lamps, so it's greater than ~2' in circumference; and also so the footprint is more homogeneous in terms of irradiance. Mercury vapor UV-b lamps are directional, so I am thinking about using a reflector and pointing the lamp toward the reflector (away from the canopy) and using reflected light to irradiate the canopy, something like these designs:

I am thinking about building my own reflector using "spider reflector" geometry (link) to make the reflector, e.g., the first pic, and using this reflective aluminum that makes diffuse light: "sun sheet" (link). I am not very worried about re-strike, nor the the angle of reflectance that would be affected by a diffuse reflective surface. It's better to use a mirror surface (non-diffuse) if one is very concerned about re-strike and angle of reflectance.

I am also thinking about using a photography type of of reflector, re the second pic, and using angle of incident to find angle of reflectance, which will allow me to customize the footprint. In that case using non-diffuse reflection materiel (e.g., "Anolux MIRO IV - 4400GP"; link) is better, but using diffuse reflective material offers greater homogeneous irradiance.

I plan to test the footprint irradiance similar to the method used by Pico in his thread, using a Uv-b meter.

 

[B. Friendly]

every light spectrum is beneficial.
lightsabers check em out,
they are reptile lights,
from here http://www.exo-terra.com/en/products/compact_fluorescent_bulbs.php

 

[spurr]

B.Freindly,

See the paper I posted about those low watt reptile lamps on page 14 or 15. They emit very, very low UV-b levels, so low in fact, there is little reason to use them; especially if they are not so close the buds they are nearly though them. For sufficient UV-b we need high radiance UV-b lamps, such as the mercury vapor lamps used in Zoos.

I have been using 300w Osram UV-b lamps for some time; but all mercury vapor lamps have small footprints of ~2' in circumference, no matter how far they are placed from the canopy (due to their directorial radiance). That is why I plan to test my reflector ideas with a UV-b meter and both the Mega-Ray and Osram brands of high-output UV-b lamps.

 

[B. Friendly]

B.Freindly,

See the paper I posted about those low watt reptile lamps on page 14 or 15.
I have been using 300w Osram UV-b lamps for some time; but all mercury vapor lamps have small footprints of ~2' in circumference, no matter how far they are placed from the canopy (due to their directorial radiance). That is why I plan to test my reflector ideas with a UV-b meter and both the Mega-Ray and Osram brands of high-output UV-b lamps.

thanks bro,
and Energy Effecient Bulbs? I have a 42 watt goin under the shade also. I know a guy that uses only these bulbs and gets some good herb.
But are the Energy Effecient bulbs any good, i been tryin to get ahold of Phillips but the wont tell me the spectrum they use????????
and what's this i hear about black lights, is that a myth?

 

[spurr]

thanks bro,
and Energy Effecient Bulbs? I have a 42 watt goin under the shade also. I know a guy that uses only these bulbs and gets some good herb.
But are the Energy Effecient bulbs any good, i been tryin to get ahold of Phillips but the wont tell me the spectrum they use????????
and what's this i hear about black lights, is that a myth?

I doubt you would get noticeable THC increase (if any increase at all) from those low power CFL or fluorescent UV-b lamps. Using those lamps, if on during the whole daylength, could help reduce stretch and offer other benefits, like affecting cryptochrome mediated responses, though.

Black lights are a myth re increased THC. I don't think black lights even emit UV-b, I think they emit UV-a...