BM9AGS
Well-Known Member
LED vs HID (THE GREAT DEBATE)
The intensity of hid is currently greater than LED due to the higher intensity at the beginning of the light itself. The inverse square law shows how all light doesn't diminish the same (linerally) instead light diminishes Logerithmacially just as sound does based of its intensity:
Meaning, the distance that a light source increases does not diminish the PPFD linearly with lights of different intensity. EXP: LED at 12 inches to 18 inches is only 6 inches of distance yet the PPFD diminishes from 940 PPFD to 445 PPFD a loss of 50% over 6 inches YET a Gavita 1000 watt DE at 24 inches to 36 inches is 12 inches while the PPFD diminishes from 1044 to 481 PPFD. a loss of 50% over 12 inches. This is a similar loss to the led but it takes the HID twice the distance to match the LED's greater loss.
Here are 2, 1 plant grow rooms for example:
Grow room 1 6 foot tall plant
A Gavita 1000 Watt DE at 24 inches above canopy, providing a center PPFD of approximately 1044 PPFD at the top colas, the lower colas 10 inches down are getting a PPFD of 500, which is great!
Grow room 2 6 foot tall plant
12 CXB 3590 at 600 watts at 12 inches is providing a center PPFD of approximately 940 PPFD at the top colas, the lower colas 10 inches down are getting a PPFD of 280 which is almost worthless
So you see the HID will crush the LED in this scenario.
It's all about cubic inches of ideal PPFD which I will say is 500-1000 PPFD
here's a new grow room using the sweet spots(500-1000PPFD) of each light in a sea of green:
A Gavita 1000 watt DE at 24 inches above canopy provides inside the 1 foot by 1 foot center square at a depth of 15 inches inside the 500-1000 sweet spot. outside the 1 foot by 1 foot square all the way to the 3 foot by 3 foot square there is an average of 5.5 inches of ideal PPFD depth. However outside the 3 foot by 3 foot square there is lower than ideal PPFD for flowering
total of 9,763 cubic inches of ideal grow space
12 CXB 3590 at 600 watts at 12 inches above canopy provides a nearly full 4 foot by 4 foot square of 940 PPFD yet only a depth of 16.5 inches, that's only 4.5 inches of ideal PPFD
total of 10,368 cubic inches of ideal grow space
So you see in this scenario the LED is pretty much equal to the HID light.
now we know we need more intensity with the LEDs. If we were to add a lens to magnify the CXB 3590, or we could also increase the power from 50 watts to 100 watts each but I don't have data for increased power.
So with the Ledil Stella HB Lens and 16 CXB 3590s at 50 watts each 15 inches apart we would have to move the LEDs to 18 inches from canopy otherwise we would get light burn or really Photon bleaching. so lets look at this set up
16 CXB 3590 at 800 watts 18 inches above canopy provides nearly a full 5 foot by 5 foot square of 1000 PPFD with a sweet spot depth of 7.4 inches
total of 26,640 cubic inches of ideal grow space! which is awesome for 800 watts
so to summarize HID is still king of huge colas on tall plants but it cant compete with today's sea of green short plants! the LED of tomorrow will have the intensity to maintain high PPFD at equal depths as HID and allow you to grow 6 foot tall plants....until that time comes stick with SOG for the more efficent but lower intensity of LED.....not to add in the heating issues of hid
The intensity of hid is currently greater than LED due to the higher intensity at the beginning of the light itself. The inverse square law shows how all light doesn't diminish the same (linerally) instead light diminishes Logerithmacially just as sound does based of its intensity:
Meaning, the distance that a light source increases does not diminish the PPFD linearly with lights of different intensity. EXP: LED at 12 inches to 18 inches is only 6 inches of distance yet the PPFD diminishes from 940 PPFD to 445 PPFD a loss of 50% over 6 inches YET a Gavita 1000 watt DE at 24 inches to 36 inches is 12 inches while the PPFD diminishes from 1044 to 481 PPFD. a loss of 50% over 12 inches. This is a similar loss to the led but it takes the HID twice the distance to match the LED's greater loss.
Here are 2, 1 plant grow rooms for example:
Grow room 1 6 foot tall plant
A Gavita 1000 Watt DE at 24 inches above canopy, providing a center PPFD of approximately 1044 PPFD at the top colas, the lower colas 10 inches down are getting a PPFD of 500, which is great!
Grow room 2 6 foot tall plant
12 CXB 3590 at 600 watts at 12 inches is providing a center PPFD of approximately 940 PPFD at the top colas, the lower colas 10 inches down are getting a PPFD of 280 which is almost worthless
So you see the HID will crush the LED in this scenario.
It's all about cubic inches of ideal PPFD which I will say is 500-1000 PPFD
here's a new grow room using the sweet spots(500-1000PPFD) of each light in a sea of green:
A Gavita 1000 watt DE at 24 inches above canopy provides inside the 1 foot by 1 foot center square at a depth of 15 inches inside the 500-1000 sweet spot. outside the 1 foot by 1 foot square all the way to the 3 foot by 3 foot square there is an average of 5.5 inches of ideal PPFD depth. However outside the 3 foot by 3 foot square there is lower than ideal PPFD for flowering
total of 9,763 cubic inches of ideal grow space
12 CXB 3590 at 600 watts at 12 inches above canopy provides a nearly full 4 foot by 4 foot square of 940 PPFD yet only a depth of 16.5 inches, that's only 4.5 inches of ideal PPFD
total of 10,368 cubic inches of ideal grow space
So you see in this scenario the LED is pretty much equal to the HID light.
now we know we need more intensity with the LEDs. If we were to add a lens to magnify the CXB 3590, or we could also increase the power from 50 watts to 100 watts each but I don't have data for increased power.
So with the Ledil Stella HB Lens and 16 CXB 3590s at 50 watts each 15 inches apart we would have to move the LEDs to 18 inches from canopy otherwise we would get light burn or really Photon bleaching. so lets look at this set up
16 CXB 3590 at 800 watts 18 inches above canopy provides nearly a full 5 foot by 5 foot square of 1000 PPFD with a sweet spot depth of 7.4 inches
total of 26,640 cubic inches of ideal grow space! which is awesome for 800 watts
so to summarize HID is still king of huge colas on tall plants but it cant compete with today's sea of green short plants! the LED of tomorrow will have the intensity to maintain high PPFD at equal depths as HID and allow you to grow 6 foot tall plants....until that time comes stick with SOG for the more efficent but lower intensity of LED.....not to add in the heating issues of hid
Last edited: