light question

[drjkl1]

My northern cheese haze changed from indica looking leaves to thin sativa leaves during preflower. Now it can't handle near as much light as before. I raised the light and fixed the problem. Then I switched to a mars ts 1000 and started it at 16 inches. The next morning I had some discolored leaves and looked like a little heat stress so I moved it up to 20 inches. It still looked like it was too bright so I turned it down to 65%. The color look a little better on the new growth on the sugar leaves but idk. Does 65% at 20 inches sound like much light?
I'm at d52 and my grow isn't really worth a journal but I think I'll do one with plenty of pics because idk what the hell I'm doing and could use some advice.

 

[Mañ'O'Green]

What we want to do here is "Acclimate" the plant to the light. Start with low light - Like the sun is at a greater angle to the earth in spring providing less light. Then raise the light to a medium level like early summer and then full level like high summer. We do not need to do this over months like the sun but over a week or so will give the plant a chance to adjust to the light intensity. When ever you have an environmental question just ask your self what does mother nature do. That often will help.

It is an awesome responsibility to be mother nature to your plants.

I start my plants from seed with Blue heavy light running 24/0 until the seedlings have their first true leaves (saw tooth edges). Then Autos get light on an 18/6 schedule for the rest of their lives. I ramp my lights power up pretty fast to about 40 DLI over the first week from 18/6 I an still running Blue heavy until she shows me she is a girl then I run without the added blue. My grow lights are heavy red for flower.

I get the extra blue from these pucks they are inexpensive and work a trick:

I actually have additional Far Red, UVA and UVB lamps that I use at diferent times in the grow to do different things but that is a bit much to get into at your level. Get a few grows under your belt first because being mother nature is a big enough job to learn already.

 

[drjkl1]

Thanks @Mañ'O'Green for the quick reply. Before i got the new light I was using screw in leds because thats what I had. I basically gave them all the light they could take without burning instead of what they needed. I'm trying to do the less is more thing in my grow but I'm doing a really poor job of regulating the light. I turned my light down to 50% at 20 inches for now.
After I go burn one I'm going to start a journal with detailed info and pics. I could really use some advice on lighting if you feel like looking at it tomorrow.

 

[Mañ'O'Green]

First of all you will need about 4ft² for each plant. Watts per square foot is Bro-science and has nothing to do with the spectrum and PPFD provided to the plant. The DLI (daylight integral) is the number of PPFD presented to the plant over a day. This is the science you want to look at. Cannabis performs best with 28 - 32 DLI as a minimum and will utilize up to 60 DLI but there is a diminishing return on the light over 50 DLI. You want your lights to be full spectrum. That used to mean PAR (photosynthetic active radiation) 400nm to 700nm wave length light but new science is extending that from 350nm to 750nm.

The green in the middle has now been proven to be used by the plant as well as ultra-violet 350nm to 400nm as well as far red 700nm to 750nm.

Most commercial lights do not include the ultra violet (or enough) but can be added with other sources later. Many lights do now include the far red.

This spectrum is Blue heavy and will be better for the vegetative cycle:

While this leans red heavy and is better for Flowering.

Many lights allow for different spectrum by turning on or off or otherwise adjusting the spectrum.

Reputable Light manufacturers will have this information for you. The PPFD (photosynthetic photon flux density a measure of the photons) foot print can be a shortcut to visually find a good light once the spectrum is correct. They look like this. It gives you the PPFD for a given area at a given height. You are looking for ~1000 PPFD in the center and as much as you can get on the outsides. 1000PPFD will produce about 32 DLI in 18 hours.

This is just an example of a PPFD footprint:

Two fixtures with close spectrum and PPFD can have drastic differences (efficiency) in the watts used to produce the same light. This is why watts per square foot is Bro-science.

Many really good fixtures are red heavy for better flowering and the ChilLed Growcraft lights I run are like this. I add Blue to the Veg and early Bloom cycle by running these Blue pucks.

A far red puck can be used to initiate stretch and flowering. Around the end of week 4 (autos) after they have already shown sex you can run a far red initiator puck for 10 - 15 minutes at lights out. But be careful as this can triple the plant height and make the internode length too large. This can also be used when you flip Photoperiod plants but once again be careful with the stretch as your plants will out-grow your available height.

There are UVB Leds available now but not with the output strength of the fluorescent lamps I run for the purpose of increased terpenes and THC. I run AgroMax t5 48" HO lamps. I have 2 UVB Plus 10,000K lamps that I run the last 3 weeks of flower all day and 1 Pure UVB (75% UVB 25% UVA) that I run a couple of hours in the middle of the day for the last two weeks of flower. These UV lamps are very dangerous to your eyes and the damage is cumulative so do not run them when you are able to see the light from them. The UVB lamp can give you a very serious "sun burn" in just a couple of minutes.

These lamps are only available in the continental USA.

 

[DCLXVI]

Great stuff Man O! I was just reading about uva/b and not seeing any uvb led modules yet. Thanks for posting the fluorescent tubes you're using! I see the rapid led uva pucks but no B wavelengths yet.