LED and Lux Meter

Hello!
New grower here and first post! I have read that Lux meters aren't accurate to LED grow lights, but I put a new meter I got today under my LED and got readings! The light is a Platinum P300 LED and the meter is a Dr. Meter LX1330B. I got readings just under 40000 at about 14". While multiple sources state to keep the light away 18", the Lux meter gives readings in the mid 20000's which isn't exactly optimal and growth has been slow. I don't want to damage the plants either. With this light being a 12-spectrum 100-3w emitter, do you think the meter is accurate and trust it? I put the meter under a T5 as well as a 450MH bulb and got good readings..what do you guys think?

Bueller?...Bueller?..anybody?

If only one light meter is affordable then a PAR meter, also know as Quantum Flux meter, is the choice.

The lux meter is calibrated with the peak sensitivity at 555 nm green as that is what humans see best. Most LEDs are low in green is why the meters are not overly accurate with some brands. Residential lights are very strong on green.

The PAR meter measures all wavelengths from deep red to violet, giving a better overall picture of the light intensity.

If money is not a problem a set of red and blue meters to go with the green lux meter would allow pretty precise adjustments to be made.

Thankyou!

skimula said:

Hello!
New grower here and first post! I have read that Lux meters aren't accurate to LED grow lights, but I put a new meter I got today under my LED and got readings! The light is a Platinum P300 LED and the meter is a Dr. Meter LX1330B. I got readings just under 40000 at about 14". While multiple sources state to keep the light away 18", the Lux meter gives readings in the mid 20000's which isn't exactly optimal and growth has been slow. I don't want to damage the plants either. With this light being a 12-spectrum 100-3w emitter, do you think the meter is accurate and trust it? I put the meter under a T5 as well as a 450MH bulb and got good readings..what do you guys think?

Click to expand...

"The intensity of light is important for maximizing the rate of photosynthesis. The optimal light level for photosynthesis is 10,000 lux. Lux is a unit for measuring light intensity. Low light intensity lowers the rate of photosynthesis. However, after reaching an intensity of 10,000 lux, there is no increase in the rate. The rate of photosynthesis may in fact be lowered as chlorophyll is bleached from the chloroplast and the plant’s stomas are closed to slow down water lost through respiration."

I can only laugh at people who throw money and energy out the window trying to mimic an atomic explosion to grow plants. sorry.

most plants are accustomed to forests and not to deserts.
the world once was full of forests and were not a mown lawn of grass and monculture crops as far the eye can see burning in the hot sun.

I count my blessing then, the marijuana I grow is a desert plant, it does not like the shade a forest floor would have. In fact it will grow extremely poorly in the shade.

I try not to laugh at anyone who is attempting to learn, all of us are born as babies with our minds empty and waiting to be filled.

The maximum light a leaf can absorb cannot be used as the ambient light all day long. A bit under eight hours at maximum is all the plant can process in a 24 hour period.

Zero light at dawn blends to full light at noon and then drops back to zero at nightfall.

Simple math shows 50% of the max to be what the plants experience over the course of a full day.

Matching this can be done with a series of lights that come on brighter and brighter then go back to dimmer and dimmer as the day progresses.
Or, 1/2 of the max can be used from morning to night, eliminating the noon stress and feeding the plant right up until bedtime.

Meters are needed either way, the light the plants use is almost an exact opposite of the light humans use. Our eyes are unable to discern when the light is correct for the plants, some of the frequencies are invisible to us and others are exaggerated.

Almost all general purpose light meters are heavily weighted to green. Under natural light this method works because the ratio of colors in the spectrum remain unchanged.
Artificial light is the color the designer makes it and a green weighted meter will not have a clue about the total spectrum or whether the light emitted will grow a plant.

Pot is a weed and can grow under most any circumstances. Pot grown well is almost a separate species over randomly grown. This is why folks track my harvest times and wait in line for limited production. The difference is worth it.

Lighting sold as 'grow light' will grow plants, some better than others but all of them will function. The standard meters are close enough when using these lights to set up a proper growing area.
LUX, lumens, foot candles, umol, PAR, all of these use a different scale and the numbers get confusing.

Whatever meter is being used take it outside at noon and aim directly at the sun. Divide by two for a start point in the bud room.
Adjustments can be made from there for different strains, Sativa likes brighter than Indica. Most marijuana is hybrid so trial and error are used for fine tuning.

Playing with plants is not work, this is my retirement hobby and I enjoy it greatly. Smoking is a happy result but the garden itself is the mainstay of my twilight years.