Just a lil info on panels,
i will compare them to COBs and why COBs are better then panels tomorrow.
When you have a panel thats rated 100K Lm (overall), but it covers a 4 x 4 in size, you cant make the claim that you hit the entire 4 X 4 or even a certain spot within its size with anything near 100K Lm, because the diodes are spread across the whole fixture and shed light to every spot on the canopy not just one spot (as opposed to HID mainly and COBs also), You can understand from this that adding up Lm in a QB or panel fixture can never apply in real life applications or to give any credit to this kind of claims, a 800w led panel fixture (like i have right now) will give avg umol of 900 to every section of the canopy within a 4 x 4 when driven to max output and at a height of 8 inch.
What does all this mean ? basically, you are getting 900 avg umol with more then 750 watt of electricity and not less heat then a HID 600,
So far it all sounds nice, 900 umol at every corner of the canopy at all times ? hard to beat that !
The problem starts when you start to go deeper in the canopy, i have my 800w panel at 6-8 inch right now, but my buds are easy 15-20 inch long so my panel is actually further then 8 inch, only the tops get the 8 inch power, (and u see this mainly with QBs or panels, the tops look rather good and 2-3 inch below it starts to look like cabbage)
Wonder why ? its because in terms of Lm output (with additive Lm count of nearby diodes), the diodes dont have enough power (Lm) to push those values (PAR) further down the canopy, its a no brainer, if at 8 inch you got X Lm then to measure penetration you need to apply same math like you measure PAR values from light to canopy, the thing is because there is a canopy in the way, its not like doing it with no obstruction.
So if at 8 inch i got 900 umol, at 16 inch i got 650 umol, and thats without nothing in the way ! so you can understand why penetration is so important and why the light diminish so fast when going through canopy.
You can also understand by this, that even at 800w and 8 inch height i only get 900 umol ! and thats not just at the sides, its at the center aswell.
If i used a HID i will get lower values (PAR) at the sides and higher values at the center, how high you ask ? well at 8 inch height with 2 400w HPS you will get more then 3500 umol directly under it, only problem - HEAT.
The thing is, those 3500 umols are at a very localized spot (usually around 1 x 1), but with 2 of those you expand that to 2 x 2 coverage, so lets say we put this setup inside a 4 x 4, we cut the numbers in half, so we get something around 1000-1500 umol across the canopy (maybe more)
Sounds pretty much like the LEDs setup... arent we forgetting something ?
Well, those 400w each (i say each because we cant add their Lm, just total it) has 55K Lm that comes from 1 source and goes directly into the 2 x 2 under it, pushing those PAR values way deeper then any lower intensity light can ever push while maintaining a higher intensity down the canopy.
You need to understand that a single light source (no matter HID or LED, well, LED is more efficient) that push high amount of Lm will always be superior to a single light source or many that push low amount of Lm.
This is the reason large commercial ops are putting 1000W HID 5-10 FT from canopy and still get decent results, and why commercial ops that use LEDs put them no more then 12 inch.
You also need to realise im talking about quality, not qty, as qty is much more easy target to reach, i saw the other day some dude on other site that got 600g from a 280w UFO inside a 4 X 8, but brother, i tell you, i wouldn't smoke that shit even if u pay me
