Switching from 18 Hours to maybe 14 after Strech?

[automan2]

Being a perpetual grower for couple decades, I've not missed any yeild that may have occurred since I burned all the evidence anyway....
My first foray into autos was through 12/12 so I just rode along but being an old engineer, I always looked into how to get the most out of the least and with a perpetual grow, why not .....
Oh I've tried the 24/0, 18/6 etc...but found that the laws of diminishing returns applies to everything....the increase in yeild will not equal the increase in cost percentage-wise.....so it's not an even trade....
If you think you'll miss that meager amount in yeild, just plant another one.

 

[Cringer]

Understanding LED Grow Light Metrics

Metrics Matter… Wait, What Are Metrics? Trying to find the best grow lights for your application can be an overwhelming process. In fact, researching the topic might leave you with more questions than you started with. After all, not all of us are qualified engineers or plant physiologists, and...

chilledgrowlights.com

It's a lot of go over but those videos might help. These metrics will help you determine optimal lighting for your space. Do you have a link for the lights you own? I may be able to help you find the right amount of time or minimal that you can run with your current equipment.

4 x https://todogrowled.com/en/tgl-led-grow-lights-/189-tgl-star-60.html

 

[Death The Cultivator]

4 x https://todogrowled.com/en/tgl-led-grow-lights-/189-tgl-star-60.html

They don't have any ppfd charts, just general distances for each stage.

I think you have enough light in that space that you could flower at 12/12 but I don't have a definite answer without a PAR meter or a chart from the manufacturer

 

[Delps8]

Per the references that others have posted, DLI is similar to the amount of rain that falls in one area in one day, PPFD is how fast it's raining. Research shows, Bugbee being one researcher, that photosynthesis increases as DLI increases. The amount of foliage ("inflorescence") increases as photosynthesis increases and the amount of flower as a percentage of the inflorescent increases as PPFD increases. There's plenty of evidence-based information on this.

It is true that, as PPFD increases past about 500 PPFD, the rate of increase in photosynthesis/yield begins to drop compared to the rate of increase in PPFD. The "yield curve" does not flatten out (in a non-CO2 environment) until very light light levels (800 - 1000 µmols). Also, the quality of the crop increases as light levels increases, as long as light is the only limiting factor in the grow environment (ie nutes, temperature, RH, water, etc. have to be squared away).

Research indicates that, for commercial growers, it is cost effective to increase light levels to the light saturation point (800-1000 µmols without CO2 and 1200 to 1500 with CO2, depending on CO2 concentration). The reason for this is that cannabis is a very high price product so, even at high cost for electricity, the marginal revenue from the increase in yield far exceeds the marginal increase in production costs.

For the home grower, it may well be worth it to ensure that you maintain high DLI's. I live in Southern California and some electricity rates are 61¢ per KwH. Despite that eye watering cost, if I were to run my 320 watt light at 200 watts, I would save, at most, $50 per month yet that $50 per month will only get me ⅛ ounce of weed at the weed store. In Coloredo, in contrast, electricity is much cheaper and I can get weed for $110 per ounce. At that price, I cannot justify growing my own weed.

In short, if you decrease DLI, yield and crop quality will decrease. Whether it's worth it to any particular grower can only be determined based on the factors for that specific grower/grow environment/location.