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Epistar 3W LEDs are that bad?

Thermodynamics is beyond my scope, but yes perhaps entropy ? Is that when energy moves from one form to another ?
 
Yes man, I've been thinking about the lens. But how can I know how far the light is reaching? I need to find some data about these LEDs and work some height for it.
 
Ohnestly, theres no easy way to estimate how light will behave. Some understsnding in light physics will give you some idea, but for the best calculation, the use of a model/simulator would be required. Which there probably are, but would demand accurate data on the light source to be calculated efficiently.

For some guidelines, LED's close together with narrow angle lens such as 60° will converge light more and focus heavily around the center, giving good vertical uniformity but horrible horizontal uniformity. Likewise, if you use LED's wide apart with wide angle lenses such as 120°, light will diverge more and you will get better horizontal uniformity, but worse vertical uniformity. Also the wide spread will cause some additional loss of light through reflection on walls or completely missing the intended canopy.

I think this may be partly the reason for why LED's are hung higher, they dont necessarily produce higher radiant flux, its just that the nature of solid state lighting and design, typically creates a light source that is heavily focused in the center, preventing the light from being closer.

I have always advocated that the ideal light source is one that is wide with narrow reflectors or lenses as this allows the light to be as uniform as possible.
What you will want to achieve is building the fixture as wide as possible (within the constraints of the budget) with the angle of the lens dictated by the size of the fixture. You could even go as far as putting wide angle strings in the center and narrow angle strings on the outside. Theres quite a few options. How you design this should also be built around how high you hang your light source, the higher the hang, the more narrow the directivity. The lower the hang the wider.

At the end of the day it would probably require just some trial and error. But man, the more and more i have thought about it, the more i see how not simple it is. Not that i thought it was easy but the diversity of thinking involved if you really want to do things right. Im sure a half asses build would do ok, but i aint that guy.
 
Today is holiday here in my country so I have some free time, I'll see if i can find some numbers having the ViparSpectra as a model. They have a map of umols for different heights and they use the same LEDs than me, but they are 5W not 3W and the lens are 90. I'll see if I can calculate it. Hope the map from ViparSpectra is trustworthy
 
A related bit of info: I switched from MH and HPS to LEDs last year and selected fixtures based mostly on price. At the time, that seemed to be the 'Roleadro' series, with a 300W fixture selling for $70 on Amazon. They did exceptionally well during the veg phase, and were MUCH cooler than the discharge bulbs which is very important in my location. Overall, a lot of bang for the buck and I'm still entirely happy with them. My plants definitely like them a lot. Their light looks almost white to human eyes, but actually has several spectral lines.

The one thing they did NOT do well was push plants into flowering mode. Just shortening the hours of light took way too long last time. This season I invested in a couple of obsolete (hence reasonably priced) fixtures with switches for both veg and flower. Adding two of those in their 'red' flowering settings made the transition very fast. Bottom line is you may find it easier to design your homebrew fixtures with the option to switch in extra red (and or blue) LEDs as required. The industry has moved away from this approach, but if it simplifies your circuit design, it may be worth considering.
 
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