I've been a lurker on RIU for a few months, soaking up as much information as I can. During this time frame I've built multiple grow concepts, re-built them, and now have one completed harvest under my belt. I'd like to thank the members of the forum for their contributions to my success. Because of this, I'd like to give back to this community with a tool I've developed called the Photosynthetic Spectral Quality Calculator. What is it? The Photosynthetic Spectral Quality Calculator (PSQC) is a piece of software I have developed to evaluate the photosynthetic "quality" of any spectrum of light. This tool can help you model different light concepts based on data from manufacturer datasheets. It's important to note that this tool is not specific to COB LED's, but rather any artificial light source. My goal for this project is to simplify the gathering of information and empower people to make their own choices with regards to their lighting. We all want the same thing... the best way to grow cannabis. What is it used for? The PSQC is used to evaluate the quantum efficiency of radiation (QER) and the luminous efficiency of radiation (LER). These two metrics are essential for modeling PPF and subsequently the PPFD of a light source. @alesh and @SupraSPL have already demonstrated the math behind this in this thread http://www.rollitup.org/t/math-behind.868988/ . Once you have QER and LER you can calculate the PPF of a light source using the following formula: PPF= (LE/LER)*P*QER LE= luminous efficiency of your light ie. the lumens per watt (lm/W) of your LED at a given drive current LER= luminous efficiency of radiation ie. the lumens per watt (lm/W) of a 100% efficient light source of the same spectrum P= the power (W) that you are driving the LED at (Volts*Amps) QER= quantum efficiency of radiation ie. the number of photosynthetically active photons per watt per second (umol/J) or (umol/W/s) PPF= photosynthetic photon flux (umol/s) Math...great...okay, how do you actually use it? Digitize the spectral distribution you want to analyze from the datasheet. I used WebPlotDigitizer http://arohatgi.info/WebPlotDigitizer/ and it made the job extremely easy. You should digitize the entire visible spectrum(~380-~780), not just the PAR spectrum (400-700). Create an excel file with a sheet called "Spectral Distribution" with column A being the wavelength in nanometers and column B the relative intensity of that wavelength in decimal form (not percent! ie. 0.22 not 22%). I've added a file called "Example Spectrum" so that you can test run the program and check your formatting. Install the software, run it, and load your excel file that you want to analyze Ensure that the spectrum looks correct Hit "Run Calculator" and the software automatically determines the QER and LER (may take a few seconds) Fine and dandy! Where do I get it? The software can be downloaded from this link https://drive.google.com/open?id=0B1eQNepXLsV0MU01U2h6VnNqRm8 OR you can download the attachment in this post. Installation Instructions Dependancies: MATLAB runtime (automatic download) and Microsoft Excel (to make the excel file with your spectral distribution) Download the PSQC_1.0.zip file and unzip it Run the PSQC_installer.exe file to install the program (This should also download the MATLAB runtime which is required to run the software, be patient, the runtime can take a few minutes to download) After installation you can run PSQC.exe from your program files or programs list Future Plans If people like the tool, then I am happy to make revisions/updates, which could add a greater degree of functionality. I do this stuff because I like to tinker, so please be patient (this ain't my day job). If people want to see the MATLAB source code then I will happily provide it, but I have no plans to convert this tool to C++ or Python because I'm simply not very adept with those languages. Feel free to comment on any errors you may see, I almost certainly will have made some mistakes.