What's More Important PPFD Or Umol?

Ok I'm a little old school & understand the principles of light for growing but some of the new terms like...

PPF & Umol - well we didn't get this with HPS, MH or CFL etc !

I have been looking at led panels with all relevant information relating to the above measurements, so what I'm trying to begin to understand are these measurements or balance of them to achieve a suitable harvest.

The old skool in me, relates this to what gets more yield a 250w or 600w HPS = that is easy answer.


Correct me if I am wrong ?

PPF is the light foot print over distance which degrades at various heights & if you may of been so lucky enough to see a grid reference of such Ya know what I mean.

How ever Umol has got me really stumped & I'm not sure how this plays out in growing or in related maths to the question at hand ?

Umol/joul is all about light pentration
PPFD is about temps
nows there is PDV or P ?? which is keeping the grow room at a specific temp and humity, foroptium growing (need an air-tight room ,excellant way to grow anf get monster yields !)

harris hawk said:

Umol/joul is all about light pentration
PPFD is about temps
nows there is PDV or P ?? which is keeping the grow room at a specific temp and humity, foroptium growing (need an air-tight room ,excellant way to grow anf get monster yields !)

Click to expand...

What? I think this is closer to correct.

Umol (micro mole) is a measure of light intensity.
PPF is the measurement of umol per second over 1 sq meter
PPFD is the instantaneous measurement of light over a square meter
VPD is vapor pressure deficit, which is calculated using heat and Relative humidity

I don’t know that one is more important than the other, they all are related. When looking at PPFD not only the light is a factor but the reflecting hood, wall, floor and ceiling color, etc.

Hook Daddy said:

What? I think this is closer to correct.

Umol (micro mole) is a measure of light intensity.
PPF is the measurement of umol per second over 1 sq meter
PPFD is the instantaneous measurement of light over a square meter
VPD is vapor pressure deficit, which is calculated using heat and Relative humidity

I don’t know that one is more important than the other, they all are related. When looking at PPFD not only the light is a factor but the reflecting hood, wall, floor and ceiling color, etc.

Click to expand...

Thanks ! you are correct -(my early morning thinking sucks !!!)

Hook Daddy said:

What? I think this is closer to correct.

Umol (micro mole) is a measure of light intensity.
PPF is the measurement of umol per second over 1 sq meter
PPFD is the instantaneous measurement of light over a square meter
VPD is vapor pressure deficit, which is calculated using heat and Relative humidity

I don’t know that one is more important than the other, they all are related. When looking at PPFD not only the light is a factor but the reflecting hood, wall, floor and ceiling color, etc.

Click to expand...

Thx!