chazbolin
Well-Known Member
RIU is blessed with some pretty astute readers and contributors. But I've always believed that when considering the variety of grow lighting technologies it has been a real challenge for the average person to determine what it is they need to understand when comparing different grow light technologies and/or brands. You really can't blame them when every manufacturer claims to make the 'best' grow light. So yes it is hard to know what to believe. I'm hoping to help eliminate much of that confusion through a simplified process of understanding the important metrics they should have been given from the grow lighting manufacturers.
If we were to take any grow lights performance characteristics down to 4 basic performance metric that every grow light manufacturer should provide us than we could talk about comparisons between technologies and brands without all the hype and misdirection. I believe this can be done as follows;
Photosynthetic Photon Flux (PPF): The total number of photons being emitted from the grow light within the 400-700nm Photosynthetically Active Region (PAR).
Spectral Power Distribution (SPD): As a relative PAR intensity shows the spectrums these photons emit.
Actual Watts (AW): The actual 'watts at the wall' value that at full power setting, the light draws at the plug.
Percentage of Area Covered Loss (PACL): Manufacturers will give a recommended area of coverage for their grow light to cover. This recommended area of coverage is determined by the manufacturer to be the "sweet spot" that the lamp:canopy distance should be set at so as to guarantee the greatest uniformity of coverage within that region. The problem is consumers are often left to take their word for that area coverage without any supporting data to confirm or compare. PACL will help to change that.
What PACL does is provides the highest to lowest intensity value within the area coverage region and represents it as a differential percentage. Since this is strictly an intensity value we're talking about here that value could be stated in lumens, lux or PPFD. It won't matter. What will matter is the uniformity of coverage within that stated area.
Here's how it would work from a testing standpoint. I'm a manufacturer that has my new grow light put into a calibrated integrating sphere. Usually this is done by a 3rd party lab so that there is no doubting the validity of the acquired data. PPF/SPD/AW is the standard data given from the lab in these reports. If the manufacturer requests a photometric report that is given as the number of photons being emitted from that light which strike a surface within a given area. In other words this is information that is included in these reports already. What a PACL value does is take the highest to lowest intensity and give that as a percentage of loss within the recommended area of coverage. The higher that number the worse the overall distribution is within that recommended coverage area.
Here's how it would work from a publishing /specification standpoint and what the end user could take away from knowing this value. In this exercise we'll take some random number high/low values that would be measured within the defined area of coverage. Let's say we have a high reading of 10 and a low reading of 1 uMol/M2-sec. This differential gives me a PACL rating of 90%. As it relates to uniformity of coverage this is either not a good fixture design or the area of coverage is being overstated. It may even be a combination of both. Nonetheless if it is being overstated as an area of coverage be aware that you will likely need to buy another one of these lights to accomplish uniform coverage to get the results you'd be looking for in both crop quality and yields. If it is poor reflector design than you are likely to have hot spots that makes for even more difficult field remedies. Either way the buyer should aware that is not uniform coverage coming from that light and make their purchasing decisions accordingly.
Let's also keep in mind that PACL is designed to be a worse case condition. As you add reflective surfaces the outer regions values, where intensities are usually lower, will be improved. Adjacent lights will work to improve the intensities within each others recommended areas of coverage. But do understand that these are not elements that should be counted on when considering a single grow light and the area that this one light is going to adequately cover for your gardens needs. So what should the ideal PACL value be? I'm of the opinion that if I state an area of coverage for a single light that PACL value should not be above 70% and ideally be in the 50% range.
So next trade show you're at why not ask the various grow light manufacturers what their PACL value is within the recommended area of coverage and see for yourself where that conversation goes relative to, among other things, the watts per sq-ft (m) that these products consume. If nothing else you will be a better informed consumer when deciding where to invest your hard earned money.
If we were to take any grow lights performance characteristics down to 4 basic performance metric that every grow light manufacturer should provide us than we could talk about comparisons between technologies and brands without all the hype and misdirection. I believe this can be done as follows;
Photosynthetic Photon Flux (PPF): The total number of photons being emitted from the grow light within the 400-700nm Photosynthetically Active Region (PAR).
Spectral Power Distribution (SPD): As a relative PAR intensity shows the spectrums these photons emit.
Actual Watts (AW): The actual 'watts at the wall' value that at full power setting, the light draws at the plug.
Percentage of Area Covered Loss (PACL): Manufacturers will give a recommended area of coverage for their grow light to cover. This recommended area of coverage is determined by the manufacturer to be the "sweet spot" that the lamp:canopy distance should be set at so as to guarantee the greatest uniformity of coverage within that region. The problem is consumers are often left to take their word for that area coverage without any supporting data to confirm or compare. PACL will help to change that.
What PACL does is provides the highest to lowest intensity value within the area coverage region and represents it as a differential percentage. Since this is strictly an intensity value we're talking about here that value could be stated in lumens, lux or PPFD. It won't matter. What will matter is the uniformity of coverage within that stated area.
Here's how it would work from a testing standpoint. I'm a manufacturer that has my new grow light put into a calibrated integrating sphere. Usually this is done by a 3rd party lab so that there is no doubting the validity of the acquired data. PPF/SPD/AW is the standard data given from the lab in these reports. If the manufacturer requests a photometric report that is given as the number of photons being emitted from that light which strike a surface within a given area. In other words this is information that is included in these reports already. What a PACL value does is take the highest to lowest intensity and give that as a percentage of loss within the recommended area of coverage. The higher that number the worse the overall distribution is within that recommended coverage area.
Here's how it would work from a publishing /specification standpoint and what the end user could take away from knowing this value. In this exercise we'll take some random number high/low values that would be measured within the defined area of coverage. Let's say we have a high reading of 10 and a low reading of 1 uMol/M2-sec. This differential gives me a PACL rating of 90%. As it relates to uniformity of coverage this is either not a good fixture design or the area of coverage is being overstated. It may even be a combination of both. Nonetheless if it is being overstated as an area of coverage be aware that you will likely need to buy another one of these lights to accomplish uniform coverage to get the results you'd be looking for in both crop quality and yields. If it is poor reflector design than you are likely to have hot spots that makes for even more difficult field remedies. Either way the buyer should aware that is not uniform coverage coming from that light and make their purchasing decisions accordingly.
Let's also keep in mind that PACL is designed to be a worse case condition. As you add reflective surfaces the outer regions values, where intensities are usually lower, will be improved. Adjacent lights will work to improve the intensities within each others recommended areas of coverage. But do understand that these are not elements that should be counted on when considering a single grow light and the area that this one light is going to adequately cover for your gardens needs. So what should the ideal PACL value be? I'm of the opinion that if I state an area of coverage for a single light that PACL value should not be above 70% and ideally be in the 50% range.
So next trade show you're at why not ask the various grow light manufacturers what their PACL value is within the recommended area of coverage and see for yourself where that conversation goes relative to, among other things, the watts per sq-ft (m) that these products consume. If nothing else you will be a better informed consumer when deciding where to invest your hard earned money.
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