Sure, let me know when you are ready…
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Some more information regarding DLI. This is the abbreviation for daily light integral (DLI). From this point forward in this description, I’ll adopt the daily licorice intake alternative in honor of one of Overgrow’s DIY experts @anon32470837. I like that term much better.
Daily licorice intake is the total amount of light a plant receives in the course of a day. It is a relatively straight forward concept and is measured in mols of photons. Many lighting manufacturers will provide you with an estimate of the PPFD that the lamp will output. If you know what your light is producing in PPFD (umols / m^2 s), you can calculate the DLI of your crop.
For instance, looking at the sunlight example again, we see that we are receiving 1580 umols / m^2 s of light in the PAR range. IF this light intensity was consistent throughout the day (we’ll assume it is for simplicity, here), we can calculate the DLI. For a 12 hour lighting period, we have:
1580 umols * 3600 seconds/hour *12 * (1x10^-6) = 68.256 mols.
Likewise, if we look at a lamp, let’s say we have 900 umols of irradiation over a 12 hour period:
900 umols * 3600 seconds/hour *12 * (1x10^-6) = 38.9 mols.
So, in the case of sunlight we are seeing a DLI = 68 and for that of an example lamp, DLI = 39 mols.
Why is this useful?
An optimal amount of daily licorice intake will optimize the amount of product your crop will bare. For day neutral fruiting crops such as tomatoes, the suggested DLI is between 20-40 mols per day. We could run the lights for 18 hours, for instance, and we’d require:
(1x10^6 * 40 umols) / (3600 seconds / hour * 18) = 617 umols / m^2 s
For short day plants, such as cannabis, the suggested DLI may similarly be around 20-40 mols per day but, the length of the day during flowering must remain short. In this case,
(1x10^6 * 40 umols) / (3600 seconds / hour * 12) = 925 umols / m^2 s
As you can see, to optimize your crop lighting for short day plants, you’ll need to provide more light as compared to long day or day neutral crops.
Can I supply more DLI?
Sure, with a point of diminishing returns. The number of mols a plant can handle before entering into photo-inhibition, photo-respiration, non-photochemical quenching, or being damaged by too much light varies on the type of crop and the conditions of the growth environment. This may include considering the vapor pressure deficit of the environment, amount of CO2, temperature, etc. There are great discussions. many here on the Overgrow, surrounding ways to “push” your plants with a higher than normal daily licorice intake. There are also many research papers that discuss what happens with too much light. There are also suggestions / research that indicate photosynthetic efficiency may decrease as the light intensity increases beyond a certain light intensity and before damage occurs.
Example of photosynthetic conversion efficiency with increasing light intensity:
At low light, more than 80% of the absorbed photosynthetically active quanta can be used (18), but at one-half of the full sunlight (∼1000 μmol m−2 s−1), as little as 25% of the absorbed quanta are used; at full sunlight this value falls to <10% (69). “Improving Photosynthetic Efficiency for Greater Yield”, Zhu et. al. (2010)
Can I supply less DLI?
Absolutely. In fact there are some quite amazing results by some folk on Overgrow that are supplying exceedingly low DLI. It is likely that you will not see the plant reach it’s full genetic potential and may give up some potential dry mass and vigor. But, you will be saving a great deal on overall energy consumption and equipment. Figuring out the balance is the difficult part. Some take this to be a great challenge to tackle.
For natural light growers in the US, refer to the following paper for estimates of the DLI in your growth region Mapping Monthly Distribution of Daily Light Integrals across the Contiguous United States
Here is some information for suggested DLI for different plants:
Another suggestion on DLI for cannabis can be found in:
http://www.cannabissustainability.org/wp-content/uploads/2016/11/Energy_Neil-Yorio.pdf
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Glad I could be of assistance 
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SPYDR 2i has been ordered and I’m awaiting assembly and delivery. I can’t wait to contribute more data to this thread 
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Yoooo…am I using google wrong or is that a $1500 meter?
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Uh, yea. That’s a scientific spectrometer. Not your standard PAR meter and not for the faint of heart. Both from a cost perspective and set-up perspective (careful ebay-ing can get one cheaper). The fiber optic cable alone runs several bills. But, but, you can do some really cool and potentially valuable things with one.
There are other more cost effective options depending on what your goals are.
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Whatcha think about that meter?
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That’s considered a good PAR meter. 
Dr. Bruce Bugbee’s company. It will not tell you spectral content but it will give you the PAR.
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Cool! I’m going to order me one of those soon. For science
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As it turns out, I have a Ray 22 which I believe is the Physiospec Indoors, which will be off line for about 2-3 weeks.
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Are you looking to measure it? Could always swing by there at some point…
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Not for my needs, but, for science.
If it is of interest, it is available for the next 2-3 weeks.
Its a heck of a trip to put a meter under a lamp, but if you are ever in the area, would be psyched to catch up.
99
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Ok, cool. Let’s coordinate in PM and I’ll try to swing by there.
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Hey Northern, can I ask you about your PAR readings? How are you determining them? Single point measurement at the center of the field? Average of multi-point readings across an area? Without an integrating sphere, isn’t a singular PAR number misleading/inaccurate, or at least inadequate to measuring the “usefulness” of a lamp’s output?
Have you measured PPFD or done any mapping of the Fluence lamps? The company is quite cagey about its data these days, refusing to release PAR maps or PPFD data on its lights.
Seems to me, for plant growers, the key metric for evaluating output from a horticultural lamp is how well does the lamp deliver the maximum usable level of PA photons to every point (evenness) across a given area from a given height, i.e., the PPFD/PAR map. Is a singular PAR reading any more than a bragging number like horsepower to a car, it tells you something but hardly enough to base a purchase decision on?
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Yes, for the above plots, single point. 18 inches from the center of the fixture. Using an cosine detector (I also have a small integration sphere, fwiw) and a lab-grade spectrometer. Spectra power is numerically integrated across the spectrometer bins to determine a variety metrics such as the noted PAR, YPF, etc. e.g. “All spectrum set at 100%, open air, single point, 18” distance from center of lamp." It should be considered a “best” case type of measurement as far as intensity is concerned. The single point measurement is something of an industry standard, not really my doing.
A C++ version of the source code for the numerical calculation portion can be found here:
Not for the plots in the OP. Each set of data in the OP includes a statement on the measurement parameters.
Cosine detector. These are for measuring luminous flux and commonly used in radiometry for measuring spectral irradiance incident on a planar surface.
Misleading? Standard industry/scientific terminology and measurement techniques used throughout, to the extent of my resources.
Such data “could” be used to mislead if it is used out of context or the the measurement parameters are misstated, I suppose.
Inadequate. I assume when you say inadequate you mean “not enough information” to numerically design a grow room. E.g. PPFD over a defined area. I’d agree with that.
PPFD + PAR mapping is a desirable metric, and is correct if that is what your are referring to. It is additional work which, if someone requests it for a specific scenario, I’ll consider looking into it. In fact, I did consider spending the extra time but I have a variety of other projects that also need attention (plus, I needed to put the lamps into service). FWIW, open space, enclosed space, reflective walls, diffuse walls, etc have much more effect on the PPFD measurements than the single point, so the space would need to be well defined. Also, I’d argue that many other metrics are equally desirable, such as the actual spectral output, conversion efficiency (using the single point), and so forth.
edit: I’ve posted some additional notes on PPFD and how it relates in the thread below.
Well, this thread was not intended to provide such information. What it does provide is a piece of data for a limited set of commercial fixtures that might be useful in that scenario. Or, for whatever other considerations. It’s another tool in the toolbox.
What data is provided could be useful for making a rationale judgement as to whether the measured data, at least, lines up with the manufacturer claims. Or, it could be used to guide the tuning of the spectra in your grow environment. It’s data, not intended for use for pitching sales. The data can be useful in a variety of ways. It does require that the individual is able to interpret that data properly. As is true with most things in life.
The equipment required to measure spectra can be complicated and expensive and, as such, most do not have the resources and have little choice but to trust that the manufacturer is being truthful. And (how I feel about), making such data openly available certainly provides much more value than what many manufacturers provide for data which, in this industry, is the typical claim that the “car” has a V8 when in reality it has nothing more than a 4 cylinder.
To be thorough when evaluating a purchase, let’s see:
Cost
PAR spectra
Spectra outside of PAR
PPFD
Spectral Control (e.g. programmable spectra)
Control interface (dimming, etc)
Power dissipation / Conversion Efficiency
Waste heat elimination (passive / active)
Weight
Footprint
Safety Certifications
Environmental Sealing
Warranty
Wasn’t really the intent of this thread. It was mainly to provide spectral information on the fixtures I have access to. Perhaps adding additional fixtures as time and access allows. But, yea, we started to get into DLI and stuff…
Although, there may be a valid reason to go through the effort of compiling such information in a different thread. Just a bunch of work waiting for the value proposition.
Interesting, are you referring to their new generation of their lamps? If there is a concern about the accuracy of data on a specific fixture, we can set-up a scenario to gather our own data. That is, if the fixture is available.
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They tell you the total PPF of the light, that’s enough for me. IMO It’s the only stat that matters and many companies don’t give it to you. It defines the amount of light coming out of the fixture. The beam angle describes the coverage area. Just divide the total PPF by the area being covered to get the intensity on the plants.
For example this 900 umol/s fixture in a 4X4 tent (1.5 square meters) gives you 600 umol/s/m. 900 umol/s divided by 1.5. Cannabis needs 600 for flowering so it fits a 4X4 tent. I just ordered one these btw. 
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I think I understand what @Baudelaire is getting at.
PPFD is an easier way, perhaps more accurate way, to determine the irradiant energy at any point on a plane within a room. At least a general depiction instead of having to calculate the radiation angles.
It makes it easier to to design the spacing and number of lamps needed to gain even coverage in a room before purchasing fixtures. The energy is there, how it spreads can be more complicated.
I know for past fixtures, Fluence did provide PAR maps for for certain scenarios. I can see this being a concern for those who have a designated space and want to get optimal / even coverage right on the first try.
On the otherhand, measure, move, and adjust may be just as straight forward as long as the energy output is known beforehand.
mmmm, a bit jealous over here. Can I measure it 
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sure, but it’s Greenhouse, will probably be the same spectrum as yours. I’ve decided to go with white lighting in veg and flower to avoid stressing the plants. They weren’t liking the shift from white to 80% red light.
I’m still not understanding the PPFD concept, wouldn’t multiple fixtures intrude on each others’ footprints and throw off the PPFD map anyway? I’ve never had to design a light map for a room or calculate the best number of fixtures for a space, what is the metric you’d use with PPFD?
PS here is a geeky video on the new shorter Vypr from the University professor that I liked, you can see it in his tent:
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Yes 
Depending on spacing, you’ll have hot spots or cool spots. Goal is to get the intensity as even as possible over the area the plant(s) occupy. That’s all. So, you don’t get one area which is super intense. E.g. the Spydrs are trying to achieve that by spreading the light over a large area instead of having all of the power emitted from a point source.
By having the PAR / PPFD mapped, one can determine the spacing such that the variance in irradiance across the area is minimized (before installing the lamps). There’ll always be some variance no matter what. This amounts to OCD stage two 
For small scale / small enclosures, where the lights are close anyhow, I’m really not entirely certain of how much we truly gain from the effort since, realistically, plants don’t restrain themselves horizontally unless you are really talented at scrog The enclosing space can potentially throw off the maps as well.
edit: metric is PAR measured at equal intervals from the center of the lamp over some defined area with the lamp at a defined height above the plane of measurement. I don’t know off-hand if there are standard distances. There may be.
Looks something like,
Overlapping the blocks from another lamp would be additive.
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OK, I"m starting to get it, the PPFD map tells you how evenly the fixture is covering a given area. You can use the beam angle to get a general idea of what’s going on, but this quantifies how much the light is spreading out. If you get the maps at different heights from the canopy it will help you figure out the mounting height of the lights.
I do a poor-man’s version by holding a wooden yardstick over the canopy and checking to make sure the light is equally bright over the whole length.
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