question about kelvins

T

theholahoop

Active Member
hey guys first off i wanna say you people are awesome.
but am confused about reading kelvin specs on lights.
like how much kelvin is 300 + 100k????
 
Y0da

Y0da

Well-Known Member
invisible lol :) Daylight is 5500k ( Flowering spectrum, red light eg sodium hid), vegging is at the blue end of the spectrum, say 2100-2700k eg metal halides
 
CaliJoe

CaliJoe

Member
My opinion on Kelvin is they are useless for what we do. 2 different bulbs with the same kelvin rating can have drastically different spectral outputs but when the phosphors are mixed they can have the same kelvin rating, meaning 1 bulb may work much better than the other even though they have the same kelvin rating. Most good bulbs have a spectral chart on the packaging, that is what I look at when selecting bulbs. Kelvin is used as a guide to how the human eye perceives the light, but that is completely different to how plants perceive the light.

Again, just my opinion, but if others have something to add that I may not be considering I am open to hearing it.
 
ZOMBIESxWEED

ZOMBIESxWEED

Active Member
CaliJoe said:
My opinion on Kelvin is they are useless for what we do. 2 different bulbs with the same kelvin rating can have drastically different spectral outputs but when the phosphors are mixed they can have the same kelvin rating, meaning 1 bulb may work much better than the other even though they have the same kelvin rating. Most good bulbs have a spectral chart on the packaging, that is what I look at when selecting bulbs. Kelvin is used as a guide to how the human eye perceives the light, but that is completely different to how plants perceive the light.

Again, just my opinion, but if others have something to add that I may not be considering I am open to hearing it.
Click to expand...
No, this is correct. Kelvin temperatures have nothing to do with what light the plant uses to turn into food. Plants only use the red and blue light spectrums to grow, so light outside of this spectrum is practically useless, like my roommate.
 
ZOMBIESxWEED

ZOMBIESxWEED

Active Member
Lumens are a measure of how powerful a light source is, 1 lumen = 1 candela (candle), lumen numbers also mean very little to growers except the higher the lumens the more penetration power and coverage the light has, or should have.

What dlftmyers has attached is a light spectrum chart showing what color spectrums plants absorb most, the color chart was converted to read approx kelvin temps in relation to the light color.
 
T

theholahoop

Active Member
okay so let me just clarify then, if i get a 5500 lm and 4200k light ill be fine. and is the 5500k read as 5500 + 100k or 550 + 100k or how?
 
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