Move lights further away or drop intensity?

Meanmonsoon

Meanmonsoon

Active Member
Grow Lights Australia said:
TLDR version: if you have a large fixture (lots of LEDs) turn them down and hang them closer. If you have a small fixture, hang it higher for better (more even) canopy coverage.

We compared the Photone Ap against a $1600 hand-held spectrometer (Lighting Passport) and as long as you covered the phone camera with a piece of white paper to diffuse the light, it was quite accurate.

Lifting the light
Pros: Easy to do, easy to reference (by distance from plant canopy); can give a fairly uniform coverage of light over the canopy
Cons: Wastes energy and light; doesn't reduce heat in the grow area; may run out of head height; usually reduces penetration due to wasted light and wall losses

Reducing intensity
Pros: Increases efficiency of the LEDs; reduces energy usage and heat; usually increases penetration by increasing the angles of available light that can penetrate through and under the foliage; increases life of LEDs
Cons: Lights must be constantly adjusted for growing plants (easier for plants to grow into the LEDs); reduces light footprint, which can create uneven canopy lighting if the fixture is small and the canopy area is large

Light meters are great, but every plant is different and some respond better to higher levels of light than others (sativas vs indicas for example). For that reason, a simple Watt meter (also known as an energy cost meter or wall meter) can be invaluable for setting up your lights by simply turning them down to a suitable wattage until your plants are happy, and using that wattage reading as a reference for each time you need to turn the lights up and down.
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Were you comparing photone on your 420 board ? Im not sure what to make of the values when using different kelvins and cri with or without monos lol.
 
Grow Lights Australia

Grow Lights Australia

Well-Known Member
Special Kdog said:
8 inches is too low with good lights... Get you a laser thermometer too. 16-24 has been my sweet spot. With my HLG 550, 24 inches was the sweet spot cause of heat and high PAR. With cheap vipar 16 was better.
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You need to look at the specs of the Migro because it isn't comparable to the HLG-550: https://www.migrolight.com/product/migro-aray-240w-iiii-bar-light/

Migrow recommends 6-8 inches away and according to their PAR measurements that will deliver over 900 PPFD across the centre of the canopy – which we would assume is correct given they are only 240-265W spread over four LED bars (roughly 60W per bar).

The problem is, not all plants will like that intensity. I know a lot of people in the industry suggest 1000 PPFD at the canopy, but different plants have different requirements, so while a sativa dom may thrive under 1000 PPFD, an indica dom may be happier under 800 PPFD (but again, it depends on the plant).

Having now looked at the Migrow PAR maps I am going to revise what I said earlier and suggest raising the fixture slightly to give a better spread of light at lower intensity.
 
Grow Lights Australia

Grow Lights Australia

Well-Known Member
Meanmonsoon said:
Were you comparing photone on your 420 board ? Im not sure what to make of the values when using different kelvins and cri with or without monos lol.
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Yes. We measured PPFD and it was quite accurate. I was skeptical at first because as you rightly pointed out if an ap uses a standard formula to convert lux to PPFD that formula only works with certain types of light with the same type of spectrum. It was a customer's phone and ap that we used to compare so I can't vouch for its accuracy in all conditions, but I was surprised that the readings were close to our own. I'm talking around 50 to no more than 100 PPFD (+/- 5-10%) out of sync. The trick is to use a piece of paper in front of the camera. Without the diffuser the measurements were way off. We used normal printer paper.
 
strainguy

strainguy

Well-Known Member
8 inch? Its really too low for the high-quality light. Google it, but in most cases, you can find that the proper height for LED is around 15 inch (one of the sources to prove https://growcola.com/guide/cannabis-vegetative-stage-marijuana-grow-guide-part-3/) . In your case, i would move them further away but I and use full power. For your perfect distance measurements, spectrometer is a good tool to measure PPFD. If you growing without extra CO2, 1000 PPFD is more than enough.
 
Rocket Soul

Rocket Soul

Well-Known Member
strainguy said:
8 inch? Its really too low for the high-quality light. Google it, but in most cases, you can find that the proper height for LED is around 15 inch (one of the sources to prove https://growcola.com/guide/cannabis-vegetative-stage-marijuana-grow-guide-part-3/) . In your case, i would move them further away but I and use full power. For your perfect distance measurements, spectrometer is a good tool to measure PPFD. If you growing without extra CO2, 1000 PPFD is more than enough.
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The link you provide only gives general advice and dont take into account the form factor of the Migro array: since its better at spreading the light out than the standard boxy type led it can also be hung much lower.
 
Grow Lights Australia

Grow Lights Australia

Well-Known Member
strainguy said:
8 inch? Its really too low for the high-quality light. Google it, but in most cases, you can find that the proper height for LED is around 15 inch (one of the sources to prove https://growcola.com/guide/cannabis-vegetative-stage-marijuana-grow-guide-part-3/) . In your case, i would move them further away but I and use full power. For your perfect distance measurements, spectrometer is a good tool to measure PPFD. If you growing without extra CO2, 1000 PPFD is more than enough.
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Yes, if you are using CO2 then many varieties can grow well under 1300-1500 umol/m2. With more photons synthesised at a faster rate, fewer photons are absorbed as heat.
 
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