Watts simply represent how much “power” our imaginary light is able to put out. We can use bananas as a unit of measure I could care less.
They all scale proportionally because light leaving a light source can be modeled by 1/x^2 from the x values of (0, ∞). By increasing distance and power, we’re effectively moving our canopy to an area of this curve where the change in average slope is more flattened. This translates to less of a PPFD drop off because now our canopy is situated in the part of the graph just above the x axis where the change in the average slope of the curve is minimal.
The closer to the y axis you get (aka canopy closer to the light) , the more it takes off exponentially and the values (PPFD readings) get exponentially further away from one another even over the smallest change in vertical hang distance (which is the x axis in our example).
Negative. Watts are a measure of power consumed to create light in this case, but there is no constant linear equation to the amount of light per watt. Some lights will emit 2-3x the amount of light per watt than others. You could change to bananas or anything else as you say, but it would still be wrong.
Only they don’t all scale portionally because ppf, ppfd, and nothing about all lights is ever the same.
I mean no disrespect but you’re fundamentally wrong. I have since vetted this thought-experiment with my entire Physics department, and they have verified that yes, higher is always better if you want less of a PPFD drop off on the edges and through the depth of the canopy (AND if you aren’t limited by the power of your light to achieve target PPFD from any hang height). This always holds true, and would challenge you to give a real life example of when this isn’t true. The example I gave with a PPFD reading at the top and bottom of a large tree being the same alone proves this point.
The professors I spoke with even said this would be a great exam question to ask since most people would think closer is better. The only downsides are: 1) requiring more power to achieve the same starting PPFD (at the top center of canopy) from a higher hanging height and 2) more heat will be generated as a result. I absolutely acknowledge that it’s not the best method with respect to energy savings, but that’s not the focus of this experiment.
I have provided real numbers and real readings that support that original hypothesis. Additionally, I’ve taken it a step further and underwent peer review of this idea from actual experts (since I am not one in physics). To continue to deny the results of an actual experiment and the confirmation from actual subject matter experts is really disappointing to see from a mod. I am still waiting for even an iota of evidence that contradicts this, other than just your word.
I wish you’d stop playing semantics with the word Watts and stop trying to pull attention away from what really matters — it literally has no bearing on what I’ve put forward as a principle of physics. It’s really sad to see a moderator acting like a such a sore loser, while also trying to draw attention away from the main point in a desperate attempt to save face or score some victory points in this conversation.
My guy you are so missing the point here. PPFD was the unit of measure I was using for the experiment since that what my instrument reads in, but the results wouldn’t have different, proportionally, whether I used lux, foot-candles, or some other measurement of light energy. Sure the values of the numbers would be completely different, but the actual percent drop off would be nearly identical but theoretically they’d drop off identically in an ideal system.
Seriously, run this experiment as many times as you’d like with any unit of measure you choose. The only conditions are that you have to start with the same center top reading in every hang height. You will not run into a single situation where you’ll get less drop off on the sides and through the canopy by running a light closer, assuming if we start with the same top center reading. It would quite literally break the laws of physics.
I don’t need to run it at all to know the flaw in your thinking. If you get your light too high you will lose photons that will never make it to your canopy. This will drop the ppf and subsequently drop your ppfd. That is pretty much the end of the story in making a blanket statement about getting your light higher always being better.
The rest of this is semantical, but circling back to unlimited watts, ppf, ppfd, or whatever can’t/won’t apply. Most people will run out of money to buy lights or cover the bill to run them. If you have unlimited funds, then you will run out of room to place lights. If you make the space bigger you will overload a circuit. If you add more circuits you will eventually overload your service. There is always a limit, the limit just isn’t the same for everyone.
If you go back to beginning of this thread you will see that I agree with a lot of what you’re suggesting. I suspect that your physics group didn’t consider the photon loss like the people engineering and testing these lights that depend on their success to advance their livelihood, and that’s ok. Not all of the people doing these things are great at it, but their recommendations for height above canopy have some merit, scientifical support, and logical real world applications.
