When to adjust light intensity?

[elusive]

So over the last year (when I first started growing), I didn’t really know when I should be adjusting the intensity of my lights (and it doesn’t help each light is set up differently than the next).

I kind of increased it here and there, then would dial it back if something seemed off, and then increase it again, etc. I’m sure this is highly inefficient for both my plants and my utility bill.

In my 2x2, I have a 2000/200 watt vivosun light that at its lowest setting is 40% intensity I believe, then goes to 50, 60, 80, and 100%.

In my 4x4 I have a 300 or 400 watt bar light that only has 2 switches. A turns on 5 bulbs, while B turns on 3.

I’ve seen all sorts of articles and videos on the topic, but a lot of variance between methods. Is there a “simplified” method? I.e., week 1-2 keep it at the lowest setting, week 3-4 turn it up to a mid setting, 5-6 crank it all the way up, week 7+ dial it down to 75% intensity, or something similar?

 

[MDK]

I'm in the same boat new light and kind of winging it. I figure next run I'll really get to figure it out better since I got this light mid grow.

I was at 50% up until Saturday when I went into flower and upped it to 75% but also raised it a couple inches. The light instructions say by flower ya wanna be at 100% but that would fry them right now...maybe in a few weeks or after stretch when the buds start to swell. I see other people mentioning not being able to do 100% and it wouldn't surprise me if I stay at 75% throughout flower this time.

 

[elusive]

Glad I’m not the only one feeling like this lol

Yeah, I think I had issues at 100%, but my 2x4 is pretty short which is why I’m keeping it autoflowers only since they don’t get nearly as tall, so I might be able to get away with it there.

I let my last crop go 8 weeks veg before flipping, and they got really close to the light in my 4x4, which is 6’ tall as opposed to 5’, so I’m thinking that keeping a 4-6 week veg should be long enough to prevent the height issue.

I’ve also been toying with removing the 4x4 since it’s in its own room and just using the room without a tent. How much do you think the reflective Mylar is helping vs plain walls?

 

[Rootsruler]

Glad I’m not the only one feeling like this lol

Yeah, I think I had issues at 100%, but my 2x4 is pretty short which is why I’m keeping it autoflowers only since they don’t get nearly as tall, so I might be able to get away with it there.

I let my last crop go 8 weeks veg before flipping, and they got really close to the light in my 4x4, which is 6’ tall as opposed to 5’, so I’m thinking that keeping a 4-6 week veg should be long enough to prevent the height issue.

I’ve also been toying with removing the 4x4 since it’s in its own room and just using the room without a tent. How much do you think the reflective Mylar is helping vs plain walls?

Aquaman mentioned this and I experienced it.

I go by DLI to determine how much light to give them in any given stage. I noticed, and Aquaman verified, that once you get your plants under the correct DLI they'll grow into the next phase unless your plants are growing so fast they've grown past the DLI number so you don't really have to do much other than check them with your light meter to make sure they're where they need to be.

White walls are plenty. You don't really need the mylar as reflective light doesn't add much to the overall DLI.

 

[Observer]

Or without sensors,

Read how the plants are perking up to the light or away from the light/down.

 

[Aqua Man]

Yes DLI is key but to little is far better than to much. Ppfd and duration are the key the intensity you need depends on the duration of the light cycle. Going 24-0 in autos you can get away with a surprisingly under rated light… when doing photos in flower is the only time those high powered lights are needed. Imo most push to hard with light… i cant stress enough if your going to error ir not sure then less is more.

Leaf orientation is a good visual indicator when you know your environment is good and plants are healthy.

Ill go into more details if you like after work

 

[elusive]

Yes DLI is key but to little is far better than to much. Ppfd and duration are the key the intensity you need depends on the duration of the light cycle. Going 24-0 in autos you can get away with a surprisingly under rated light… when doing photos in flower is the only time those high powered lights are needed. Imo most push to hard with light… i cant stress enough if your going to error ir not sure then less is more.

Leaf orientation is a good visual indicator when you know your environment is good and plants are healthy.

Ill go into more details if you like after work

More details is always better if you have time

 

[Rootsruler]

Yes DLI is key but to little is far better than to much. Ppfd and duration are the key the intensity you need depends on the duration of the light cycle. Going 24-0 in autos you can get away with a surprisingly under rated light… when doing photos in flower is the only time those high powered lights are needed. Imo most push to hard with light… i cant stress enough if your going to error ir not sure then less is more.

Leaf orientation is a good visual indicator when you know your environment is good and plants are healthy.

Ill go into more details if you like after work

Would this apply to SCROG growers where they are tucking branches so no vertical growth to grow into the DLI?

 

[Aqua Man]

Would this apply to SCROG growers where they are tucking branches so no vertical growth to grow into the DLI?

Its not a rule but generally speaking you don’t need to make many adjustments through the grow unless flipping to flower or if changing your lights on duration.

Again no hard rule but with a scrog you may want to increase intensity if the plant is small going into the scrog and is going to spend a bit growing out in the scrog. In veg intensity is less impact but in flower you want to maximize the light to the plant as much as possible without to much stress