Samsung 2700k led Spectrum:
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications.
classified by radio, microwaves, terahertz waves, infrared, visible light, ultraviolet, X-rays, and gamma rays
classified by radio, microwave, infrared, visible, ultraviolet, X-rays and gamma rays.
Full Spectrum Light:
Spectral range from Near Ultra violet 300nm to the end of the infrared spectrum 1000nm.
Spectral range from 10nm to 400nm.
Ultraviolet A (UVA) 315nm to 400nm
Ultraviolet B (UVB) 280nm to 315nm
Ultraviolet C (UVC) 100nm to 280nm
Near Ultraviolet Spectrum:
Spectral range from 300nm to 400nm
The portion of the electromagnetic spectrum that is visible to the human eye. A typical human eye will respond to wavelengths from about 390nm to 700nm.
Spectral range from 700nm to 1000nm (1mm)
A Black Body is reference to an opaque (unable to be seen through) and non reflective object which absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.
Black Body Radiation:
Every object radiates (and absorbs) electromagnetic waves. The spectrum of this radiation is not dependent on the chemical composition of the matter but it's only determined by its absolute temperature T. It turns out that all objects behaves like blackbodies, regardless if they are actually black or not. At ambient temperature the majority of the emitted spectrum is in the long wave infrared which is not visible. As the temperature rises, the spectrum shifts towards shorter wavelengths, this is known as "Wien's shift". At temperatures around 900 K, part of the radiation becomes visible since wavelengths in the 700 nm region are present and the object start to appear "red hot".If you think of a blacksmith working a piece of hot iron, the iron glows red because its temperature is around 1'000 K, but the charcoal in the furnace glows the same color because it's at about the same temperature, even if carbon and iron are chemically very different.
The picture below shows a nail glowing red hot when heated with a propane torch: one can clearly see the hottest part of the nail glowing yellow, the part that is just outside the flame glowing red and the rest being black because normal cameras cannot see infrared radiation. The nice blue color of the flame is not due to blackbody radiation: the temperature of a propane torch is around 3'000 K so the flame should glow yellow, but the chemical reaction taking place emits a much stronger blue radiation masking the faint yellow glow.
CCT (Correlated Color Temperature):
CCT refers to the color of the light itself. CCT does not refer to the actual temperature of the light source; instead, it describes if you were to heat a black body to 2700 degrees Kelvin, and then compare it with a light source with a CCT of 2700K, you would notice both objects glow with the same color.
CRI (Color Rendering Index):
CRI refers to how a light source renders the colors of other objects and surfaces. The CRI can reach a maximum value of 100, which means the light source in question has the same color-rendering capability as natural daylight. Color rendering is increasingly distorted as the CRI becomes lower, and there is no lower limit: negative CRI values indicate extremely poor light sources that completely distort color perception.
The lumen is a unit of measure of the quantity of visible light emitted by a source, Lumens are weighted according to a model of the human eye’s sensitivity to various wavelengths. This weighting means that light in the green-yellow spectrum will register significantly higher in lumens than red or blue light – the most important colors for photosynthesis in plants. While lumens may reflect how much light humans perceive, they do not adequately account for how much light your plants are actually receiving.
Luminous flux refers to how much light energy is emitted per unit of time in all directions, and is measured in lumens. To properly measure luminous flux, you would need to place your light in a device called an integrating sphere, which is able to measure all of the light that the source produces. Luckily, this value will be provided on the data sheet for your COB, so you can save the $10,000 you were going to buy the sphere with for something else. You can use luminous flux ratings to compare COBs against one another, so long as you have the voltage and current at which the reading was taken. If you compare 2 COBs and both are rated for 10,000 lumens, but one does it at 36 volts and 1 amp (36 watts), and the other does it at 36 volts and 1.5 amps (54 watts), the first one is more efficient and is a better choice.
Lux is a measurement of how many lumens fall on a 1 square meter surface, when lit by a source 1 meter away. 1 Lux is 1 lumen per square meter. Lux meters can be purchased pretty cheap online, but again – these are measuring lumens, and aren’t very useful for grow lighting.
A foot candle is a measurement of how many lumens fall on a 1 square foot area, 1 foot away from the light source.
PAR (Photosynthetically Active Radiation):
PAR is not a measurement of light, but a range of a light that factors in all wavelengths from 400nm (blue) to 700nm (red). The PAR range corresponds with the range of light that’s visible to humans, PAR does not intentionally weight various wavelengths of light differently like lumens do.
PPF (Photosynthetic Photon Flux):
PPF is a measurement of the total number of photons a light source emits per second that are within the PAR range. PPF is measured in micromoles per second (µMol/S). 1 Micromole is equal to 602 quadrillion photons (602,000,000,000,000,000).
PPE (Photosynthetic Photon Efficacy/Micromole per Joule):
Photosynthetic Photon Efficacy refers to how efficient a horticulture lighting system is at converting electrical energy into photons in the PAR 400nm to 700nm wavelengths measured as umol/j.
PPE = PPF ÷ actual wattage, the higher the better.
an LED light draws 300 watts and advertises 540 PPF
540 ÷ 300 = 1.8 umol/j
PPFD (Photosynthetic Photon Flux Density):
This is the measurement given from PAR meters. PPFD measures the average amount of photons in the PAR range hitting a certain area per second, PPFD is measured in micromoles per meter squared per second μmol/m2/s. Full sun on a clear day at noon is ~2000 PPFD.
Many commercial grow lights provide PPFD values, but omit critical information like the distance at which the PPFD reading was taken. Taking a single measurement of PPFD is also not worth much either – it’s better to have multiple measurements of PPFD in several different places below the light.
To Find PPFD Example:
a light advertises 500 PPF or μmol/s at 24" height.
First find out how many square meters your space is.
a 3x3 space = 0.836127 square meters.
Then take your PPF or μmol/s and divide by your square meters.
500 PPF or μmol/s divided by 0.836127 = ~598 average PPFD in a 3x3 area.
DLI (Daily Light Integral):
DLI is a cumulative measurement of the total number of PAR 400nm-700nm photons that reach the plants in a day and is represented in mol/m2/d. Plant growth is determined by the DLI. A clear summer day is 50-60 mol/m2/d, highest yields from many crops seems to be around 43 mol/m2/d according to NASA experiments.
How to Determine DLI With Grow Lighting:
A light produces 1000 PPFD which is measured per second, there are 3600 seconds per hour.
1000 PPFD x 3600 seconds = 3600000 PPFD per hour.
Divide PPFD per hour by 1,000,000 to convert umols to mols.
3600000 ÷ 1000000 = 3.6 mols per hour.
multiply the mols per hour by number of hours the lights stay on each day
3.6 x 12 hours per day = DLI of 43.2 mols/m2/d which is ideal for maximum yields according to NASA experiments.
Here is a chart of average daily DLI in San Francisco Bay in March, April, May, June, July and August:
Here are daily DLI yield results from NASA biomass production chamber: