whats the most light you have given your plant?

[tyler_ hobbyist]

Whats the most light you have given ur plant and did u notice any difference in the growth?

[DrPhoton]

3.86x10 to the power of 26. Also known as the sun.
Joking aside, the sun actually provides more energy than a plant can handle and causes most plants to drive its photosynthesis down daily in order to protect itself.
More light will always increase growth up to the point of maximum photosynthesis allowed by a plant, which is different for every species. It has been shown in cannabis that around 700-1000umols photosynthetic efficiency goes down and starts photoinhibition.
How much artificial light is required to reach that point is really difficult to calculate and actually gave me quite a headache trying to work it out. Because my math is not very good. I even had to go back to my light physics book to work it out.

To compare sunlight to artificial light, you must use one or more of the light measurement techniques available today. Using Radiometry there are three basic quantities. Radiant flux, radiant intensity, irradiance. Now of course there are many more, but these three cover most of our applications. All that these measurement techniques do is measure EMR in the form of units, in different ways. To know more, read my write ups on measurement systems.
For measuring sunlight we can use irradiance with the unit umol. This measures light over a unit of area, typically one square meter. A form of irradiance measurement is the PPFD, which is a subset of radiometry called spectroradiometry.
Using PPFD shows our sun to emit around 2000-2200umols per second over one square meter.
Now we cannot perform the same test with artificial light, because it does not act like a point source and is not uniform in all directions. Because of this, we must use another. PPF. This measures total light output. Using PPF shows that a typical 1000w HPS light, will provide around 1300umols per second. So not quite as powerful as the sun when covering a specific unit of area, however more than enough for a plant area of one metre squared.

I understand that might not make sense, it rattled my brain for hours today, thanks to you . So it may all be for nought haha.

[Tazard]

Yes I have several that are to tall and receive more light than the sun transmits to a desert on a sunny summer day. They are currently at 115k lux from HPS light. Not sure that this is what you want but nebula has a GWE topic on it and over 70k in veg and 85k lux in flower are upper limits before light damage occurs. It would be calculated differently for LEDs however.

[tyler_ hobbyist]

Thank u very much do u notice any difference from 85lx to 115lx

[Tazard]

Yes. Light burn. I let my grow control me and I'm so crowded I think I am better off burning tops than laying them over and shading lower buds.

[Tazard]

How bad will vary by strain too.

[tyler_ hobbyist]

Do u use co2 at all just curious

[Tazard]

No. My understanding of CO2 is that it only helps grow leaves and stems. Most articles I have read suggests it only be used through week 4 of flower. Although some suggested it would help during later flower. I only vegged my Acid Dough 21days from adding water to seed my bagseed was vegged 3.5 weeks longer but only so I could flower them all together. If on the other hand you veg for 3months or whatever to get 1 plant to fill a 4x4 or something then that is where my research suggests CO2 would have great potential value imo.

[tyler_ hobbyist]

I personaly use co2 and I add it at 1500ppm from seedling to harvest and I get way bigger yields and little to never heat or light stress I even added 2, 1000watt hids in a 4x4x8 space and. Didnt get light stress because of the co2 and I always get a lot better yields with it than without. Just my personaly exspereince.

[tyler_ hobbyist]

Co2 is needed for photsysthesis but plants only are able to use co2 if there is blue in the spectrum as the stamata (cells) only open with warmth 80ish and blue light. Co2 can be used at lower temps but is more effeient at higher temps

[Tazard]

I am setting up a perpetual harvest once I get it running maybe I will try adding CO2 (like I said I looked into it and a controller is the priciest item) after week 6or7 once all leaf and stem growth has stopped. imo that would be the best evaluation for it's effect on the harvest that isn't due to a vegative advantage.

[tyler_ hobbyist]

Depending on ur grow size, depends on the tank u want a 50lbs is cheaper. 20lbs tank 200bucks where a 50lbs tank is 300 and a 50lb tank will last 2 full grows from seed to harvest in a 10x10x8 room and all I do is run a regulator set at 13scfm standard cubic feet per min and I set a 2min timer ever 4hours I dnt run controllers because there to exspesive but u can buy either co2 test kits (2test) for 20bucks or a co2 motior off ebay for 90bucks and that co2 monitor does rh temp and co2 so its a win win.