Far red light

don't interrupt a dark cycle in flower, obviously.. light is used for photosynthesis. Recent studies show the wavelengths of what is typically referred to as "PAR" needs to be expanded a bit. bugby and likely others have shown some wavelengths above and below this range do impact photosynthesis. it should be with your light.. not some over-thought out complicated thing. And, it likely will not make any noticable different in the context of 2-10 plants in a small garden that a human can resolve without preceise measurements. The numerous variables at play would easily fog this out. A commecial op may not even be interested if the additional cost doesn't justify any potential improvement to productivity. You can spin around chasing your tail all day on this gimmick or that.. 90% of it is simply providing "max" dli, relative to your environment. focusing on that will give the most ROI than any other factor and 10x more important on sunday (jk.. it's the largest factor by far and away.. takling small percentage differences beyond that when worrying about CCT or this or that property of light.) bugbee has video of this expanded PAR range. i'm sure there are good tidbits to glean from that video. A statistically significant response does not mean it is something everyone should do... that depands on amplitude of the effect and cost to implement it. A correlation doesn't have to be worth it just because it is proven to exist. i used to fret about my newer lights being a "cooler" 3400K CCT compared to my previous diy lights that were 2900K. I have yet to see any difference in them. I even have both in use this grow. you can see half my garden is a bit yellow/red tinted and other side is more of a white light... have yet to definitively recognize any difference in results... that doesn't mean there isn't some measurable difference, ony that the measurable difference is so small it doesn't fucking matter much :P Provide max dli relative to co2 in your atmosphere, control your temps/rh (vpd) as best you can and small potatoe factors will never be able to be resolved with human senses in any normal context of a home garden...