When is the blue/red/anynm too much?
- Thread starter Nutria
- Start date
Rahz
Well-Known Member
Good questions, but most of the answers can only be found by testing and I don't think there's been enough testing to have definitive answers. Green is a useful part of the PAR spectrum. It drives photosynthesis, almost as well as blue and penetrates through the canopy at a slightly higher rate. However it's not the best at driving photosynthesis so there's no compelling argument to try and add more green than what is available in any of the cob options available IMO.
Anyway, I think blue/red veg/flower is left over from HID bulb selection. Some of the newer HPS bulbs and CMH have more balanced spectrums and pretty much any cob even as low as 2700K 90CRI has more blue that the older style HPS spectrum.
So, what is the best color ratio in veg? Some reading based on crop studies indicates there's no benefit (reduced stretch) to using more than 20% blue. The main driver of stretch is the percentage of deep/far red. In theory the obvious implication (if the 580-680nm range is considered highly desirable) is that 4000K 70-80CRI is the best veg spectrum as far as cob/phosphor selection is concerned. That spectrum contains plenty of blue, low deep/far red levels and more 580-680 than higher K options. Even 3500K 80CRI which contains 15% blue and similar deep/far red ratio to 4000K 80CRI would make a good dedicated veg lamp. I even know of someone running 3000K 90CRI as a dedicated veg spectrum and has no complaints.
They all grow bushes. The majority of stretch happens in the first month of flowering so if it's really a concern the plants should be hit with high K low CRI up to half way through flowering.
That's my take on it. Always interested to read other opinions or see some actual side by sides.
In the end, with any particular strain the difference on the extreme ends of spectrum choice is probably only going to be a few inches, maybe a bit more with stretchy sativas. Unless the grower is really height limited, just pick one and roll with it. Higher K and lower CRI does have more electrical efficiency but low K high CRI will have more photons per watt and the spectrum will be more photosynthetically efficient (in theory) so it's not simple math when it comes to guessing what cob will be the most efficient at producing plant mass.
Anyway, I think blue/red veg/flower is left over from HID bulb selection. Some of the newer HPS bulbs and CMH have more balanced spectrums and pretty much any cob even as low as 2700K 90CRI has more blue that the older style HPS spectrum.
So, what is the best color ratio in veg? Some reading based on crop studies indicates there's no benefit (reduced stretch) to using more than 20% blue. The main driver of stretch is the percentage of deep/far red. In theory the obvious implication (if the 580-680nm range is considered highly desirable) is that 4000K 70-80CRI is the best veg spectrum as far as cob/phosphor selection is concerned. That spectrum contains plenty of blue, low deep/far red levels and more 580-680 than higher K options. Even 3500K 80CRI which contains 15% blue and similar deep/far red ratio to 4000K 80CRI would make a good dedicated veg lamp. I even know of someone running 3000K 90CRI as a dedicated veg spectrum and has no complaints.
They all grow bushes. The majority of stretch happens in the first month of flowering so if it's really a concern the plants should be hit with high K low CRI up to half way through flowering.
That's my take on it. Always interested to read other opinions or see some actual side by sides.
In the end, with any particular strain the difference on the extreme ends of spectrum choice is probably only going to be a few inches, maybe a bit more with stretchy sativas. Unless the grower is really height limited, just pick one and roll with it. Higher K and lower CRI does have more electrical efficiency but low K high CRI will have more photons per watt and the spectrum will be more photosynthetically efficient (in theory) so it's not simple math when it comes to guessing what cob will be the most efficient at producing plant mass.
Photon Flinger
Well-Known Member
680nm and 700nm according to Emerson.