How is light intensity meausured?
The lighting industry measures light intensity in lumens. Lumens represent how intense or bright a light source is to the human eye.
For plant growth, intensity should be measured in watts (ie: 600W or 1000W lamp) or watts per square foot. Typically 40-60+ watts per square foot should be used in a garden.
What Is VCF Light Grading?
This is a new measurement of light, that is far more relative to indoor gardening. This measurement takes particular spans of nanometers that are truly relative to plant growth indoors using artificial lighting. This is a new measurement scale Genesis is utilizing to provide a true and accurate value to indoor lighting.
(V) Vegetative 400-520 nanometers (C) Carotenoid 520-610 nanometers (F) Flowering 610-700 nanometers
How Do I Analyze the Quality of a Light Source?
The spectral distribution chart is the best illustration of the quality of the light spectrum.
What is a Light Spectrum?
Light spectrum is the many different wavelengths of energy produced by a light source. Light is measured in nanometers (nm). Each nanometer represents a wavelength of light or band of light energy. Visible light is the part of the spectrum from 380nm to 780nm.
You can use these charts to compare the energy levels of various light sources used for plant growth. They are the most practical way to compare the quality of light created by different light sources. The chart shows exactly which wavelengths of light (measured in nanometers) the plants are receiving.
What is the McCree Curve?
The McCree Curve represents the average photosynthetic response of plants to light energy. The McCree Curve, also known as the Plant Sensitivity Curve, begins at 360nm and extends to 760nm. This curve can be placed over a spectral distribution chart to see how well a light source can affect plant growth.
What is PAR?
Photosynthetic Active Radiation (PAR) was derived from the Mcree Curve. It is a total count of light energy (in photons) between 400nm to 700nm.
The PAR measurement is quickly becoming a popular metric of the growing power of a light source. However, the PAR measurement has two fundamental flaws.
Wavelengths between 380nm to 400nm and 700nm to 880nm are excluded from the PAR measurement.
All photons are weighted equally regardless of wavelength. The Mcree Curve clearly shows plants respond to energy outside the 400nm to 700nm PAR range. Plants respond differently to energy within the PAR range.
A PAR meter only measures photons between 400nm and 700nm. As you can see in the example above, PAR does not distinguish which photons of light are present; it only counts the total amount of photons present in those nanometers.
Plants Sense Light Differently Than Humans
The human eye might not notice any difference in light intensity or subtle shifts in spectrum over as few as six months. Your plants will.
Our research indicates that burning lamps for 12 or more hours every day diminishes both intensity and spectrum. This happens with all lamp brands, since the chemical reactions within the arc tube (which create the light and spectrum) deteriorate over time.
Man-made lamps do wear out, and plants are quick to recognize these subtle changes. For example, think of putting an outdoor vegetable garden in a semi-shady spot. Sure, the plants may grow—but not to their optimum potential.
For fuller, thicker vegetative growth and greater yield, lamp replacement should be part of a regular maintenance schedule. Keep old working lamps for troubleshooting your system or as a temporary replacement if lamps burn out.
Lamp Replacement Guide
When growing indoors, light intensity and spectrum become even more important. The quantity and quality of light are the most critical factors associated with successful plant growth. Regular lamp replacement is essential.
What Should I Use to Compare Light Sources?
The spectral distribution chart is the best way to compare light sources. Brands that do not publish spectral distribution charts should not be considered to be legitimate purveyors of lights sources for indoor plant growth.
The Color Rendering Index (CRI) is a rating system that measures the accuracy of how a light source makes specific colors look.
CRI tells us how accurately a light source displays specific colors. They are listed below.
If a light source displays these 14 colors perfectly the corresponding CRI would equal 100. If the light source did not display any color correctly its CRI would be 0 (zero).
The CRI index was created to help companies sell products. If a light source does not accurately display colors, the carpet that you purchased in the store may look completely different at home. A red shirt may look orange or pink. A white car may look grey or cream.
Do your plants care about CRI? Only if they are buying carpet, shirts, or cars.
Some horticulture lighting brands publish the CRI values. However, CRI value has little to do with lamp spectrum or its ability to grow plants.
Lamp Coverage Guide
This chart represents the maximum optimal footprint for each of our lamp wattage levels when used as a stand alone lamp. In a greenhouse application the foot prints can be doubled.
What is the Chlorophyll A and B within the Spectrum mean?
This is the area that best represent the plants photocatalytic response to particular points within the spectral distribution chart. Chlorophyll operates most efficiently with the red and blue spectrum to capture light. Pigments such as carotenes and xanthophylls are considered accessory pigments that contributing to the process of for photosynthesis providing a connection to certain green wavelengths (though particular green wavelengths are reflected by the plant). Carotenoids peak utilization in ranges from 440-525 (violet-blue-green spectrum).