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Lighting questions for Theo (Gavita)

read the research… Of course it will not. But choosing a light source that has a lower efficiency (as in PPF/W) will give you less photosynthesis. The experiment was not about efficiency, but photosynthetic rates given the same PPFD.

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So if I put a 1000w HPS with no fan in a room, and an out of the box 1000w LED in another identical room, then the ambient temps of both rooms will be the same after 12 hours run time?

And if those two have different outputs, what should we be comparing with? Does a 1000w HPS match a 1000w LED. Or as much of the LED marketing seems to say that a 1000w LED is more equivalent to say 1500w HPS.

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nathan look up heat gain in HVAC systems. The efficiency of a light source doesn’t matter. Light doesn’t disappear, it converts into heat eventually. The light that is absorbed by a plant does not all get converted to chemical energy either. If I add 1000W of energy into a system, I must take out 1000W. So at same efficiency same power into the room for the same ppfd and same heat load.

btw did you know that it takes more energy to create a blue photon than a red photon, and that extra energy is not all used by the plant and dissipates into heat? Ergo: blue light will heat up our plant more than red?

Plants are photon counters. The energy of the photon is of no influence to the photosynthetic process. it takes about 12 photons to bind 1 CO2 molecule.

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@Theo - Here is a model I am testing at the moment. I would be interested in your professional analysis.

https://www.mars-hydro.com/ca/mars-ii-1200-led-grow-light-ca.html

Item NO.:Mars II 1200
BTU:1883
Compare to HPS/MH/HID:600w
certificate:ETL, CE, RoHS
Draw power:110V: Veg: 335w±5% / Bloom: 512.8w±5%|220V: Veg: 334w±5% / Bloom: 510.5w±5%
Amps:4.3A
Voltage: 85v - 265v
Decible value:60.4
N.W/G.W:26lb. 12KG.
Coverage:4’X4’ (122cm x 122cm)
Lifespan:50000hours
View Angle of leds:90°-120°
spectrum:440nm, 460nm, 630nm ,660nm,730nm(IR), 2700k-3000k
Plug Type:EU,UK,AU,USA,Japan
UPC Number:708747426007
Dimension:19" x 19" x 3" (46046090)mm
Hanging System:Seedling:24”-30“ Growth:18”-24“ Bloom:12"-18 "
Work Temperature Condition:85°F -105°F (30°C - 40°C)
Warehouse:CA
shipping_method:Canada post, Canpar
Chip Brand:Epistar

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If you guys prefer I can split the discussion with @nathan around the LED lighting into a separate topic, if that makes things easier to keep track of.

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I don’t mind. To me HPS vs LED is one of those issues I really struggle with. Both have their own unique benefits I think but it is great to get such detailed information from professionals such as @Theo and @clones

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lol rename the topic “Ask Theo”

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@Theo - that’s great feedback. I’m coming indoor from an outdoor and greenhouse background - testing to see what works but without the professional lighting background. Having more informed analysis to the claims is great which is why I think this thread is so important.

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Hi Theo,
Interesting observations.

Will you please share your knowledge of green light? Its significance or lack of significance?

What can you tell us about far red and its influences on Pr and Pfr?

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I would but we are getting much off-topic at the moment and I am already spending a whole free evening on a forum… time for a bit of quality time if you don’t mind.

I would really like to keep this one on topic.

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You can share your thoughts whenever you are free, we are collecting valuable opinions on lighting science and would like to hear your thoughts on green light and Far red!

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I would suggest to clean up the topic and start new ones. This is not good for the searchability of the forum.

I am sure many members can explain the Pr Pfr cycle, and there are also many resources on the internet about it. Let me google that for you: https://www.boundless.com/biology/textbooks/boundless-biology-textbook/plant-form-and-physiology-30/plant-sensory-systems-and-responses-184/the-phytochrome-system-and-red-light-response-701-11926/ :wink:

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Ok I’ll go ahead and split this topic off into it’s own topic and leave all the posts around the original topic here: Light. Specifying and measuring it: NOT so easy. I call shenanigans

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you missed one :wink:

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thanks - I wasn’t sure if that was in response to someone’s question or if it was on topic for the original thread.

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so where is the PPF in this spec?

It’s a 513 W fixture supposedly replacing 600W HPS (which HPS? Lots of 600W HPS systems ranging from 1000 - 1190 umol s-1) and for a 4 x 4. This gives it away a little: that is probably at a much lower ppfd. We recommend about 500W per square meter for high intensity, but in a small tent you have much losses. LED has an advantage there as less light goes to the walls, so less losses. To light it uniformly though you probably need to hang it high over your crop given the 90-120 degrees “view angle” (how professional) - so probably a much tighter beam angle as LEDs typical have a lambertian distribution.

I don’t know, I haven’t seen any real PPF specs.

Again, remember: a lower PPFD will give you a higher yield per Watt, but you need more space. The nugs may not be as compact as with high intensity lighting though. Scrog recommended.

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and number 2

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Absolutely correct Theo!

A watt is a watt and a watt is equal to 3.41 BTU’s. When designing spaces we round up to 4 BTU’s to allow for some additional heat sources such as burning Co2, fans, pumps and people. The real question is what are you doing with the watt and how are you delivering all the potential energy to the plant?

Brandon Kion
Excel Air Systems

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Of course, when you calculate the heat load you also take into account the climate, insulation of the room etc etc. You might need a lot more in south California. I had a great discussion in Washington with a dad and his son. He had told his son to paint the roof white to reduce the heat load, and insulate it, and his son did not believe that white pains thing. He also did not believe that a Watt is a Watt. We went to two HVAC manufacturers with him at the show to convince him. Dad was happy :wink:

I actually suggested to put some sedum on the roof. Excellent insulating properties.

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Gavita DE HPS + Gavita 300 watt Plasma model 41.01 = UVA & UVB medley + jazmonic acid = resin party = me passed out after 1 hit zZzZZZzZzzzzzZZZzZz

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