In order to grow indoors we need to use artificial lighting.  Artificial lighting replicates the wavelengths (based on the Color Rendering Index [CRI]), and lumens produced by the sun.  Humanity has invented: fluorescent lights, High Intensity Discharge (HID), Light Emitting Diode (LED), Induction light, and Plasma light.  What makes learning lights challenging is new words, terms, and importantly companies will call the same technology different things.  Companies will make up new words or rearrange words for the same technology.

How do we even know which light to buy? So much information and so much to choose from.  You might be looking to save money and grow your own medicine, your own recreational use, are a care taker, or as an enthusiast we can easily stress ourselves out and feel overwhelmed with the amount of options available and so many internet sites lacking clarity or direction.  It’s ok. Captain Sunshine will share to the best of his ability.  Let’s start with some key terms, vocabulary, and basic science that is extremely important if you want to grow with unconditional love towards your plants.

Color Rendering Index

A scale from 0-100 that reflects the colors based upon the wavelengths or spectrum of the sun

  • The spectrum is known as the visible colors in the rainbow or the scientific term is the electromagnetic spectrum representing all the known frequencies and wavelengths of photons.
  • The idea for indoor growing lights is to imitate the wavelength or frequency of the light of the sun, in order to stimulate the plant to grow indoors, just as it would it would outdoors.
  • The trick is to find the cheapest light with the highest Color Rendering Index and highest lumen
    • Unfortunately there is no app to compare all the lights on the planet for cost, color rendering index score, and lumen score and analyze the scores mean, median and mode.
      • Thankfully, we have Captain Sunshine.


  • The light the human eye sees are wavelengths between 400–700 nanometers (nm).
    • Infrared has longer wavelengths and ultraviolet has shorter wavelengths.
      • We eventually learn that cannabis desires specific nanometers at different stages of the life cycle.
      • Ultraviolet light UV-A has a wavelength of 315 to 400 nanometers.

Ultraviolet light UV-B has a wavelength of 280 to 315 nanometers.

Blue light has a nominal wavelength of 475 nanometers in a range of 400-500 nanometers.

  • In the spectrum blue wavelengths are shorter.
  • Growers who use high proportions of blue during the vegetative phase report cannabis plants to produce big healthy leaves, shorter stems which focus on leaf production, producing a more round plant towards the base of the Earth.
  • The blue spectrum informs cannabis to grow, and which direction to grow in.
  • Cannabis growers who want to focus on the blue spectrum during the vegetative phase often use fluorescents and metal halides.
  • During vegetative growth cannabis has been reported to like 430-453 nanometers.

Red light has a wavelength of 650 nanometers.

  • Captain Sunshine and friends experiences report higher values of red nanometers in flowering increases density in the flowers.

Green light

  • Has a nominal wavelength of 510 nanometers in a range of 500 – 600 nanometers.
  • Cannabis appears green because the leaves of the plant absorb every color in the light spectrum other than green. The green color in cannabis leaves is therefore a reflection of the green spectrum.

Yellow light

  • Yellow light has a nominal wavelength of 570 nanometers.
  • Orange light
    • Orange light has a nominal wavelength of 590 nanometers.
    • Low-pressure sodium lamps can project orange wavelength near 589 nanometers.
  • Violet light
    • Violet light has a nominal wavelength of 445 nanometers.
  • Chlorophyll A absorption occurs at 430 nanometers and 662 nanometers
  • Chlorophyll B absorption occurs between 453 and 642 nanometers.

Forms of light used in growing

  • Black body light emission
    • incandesence
  • Electric Current/ Electric field
    • Light emitting diodes
  • Chemiluminescence
    • Chemical reactions. High intensity discharge.


Scientific term for the process plants use to convert light for chemical energy and energy transformation. Simply the process for how plants make their food.

Photosynthesis has two stages: Light-dependent reactions and Calvin Cycle.

1) Light-dependent reactions

  • Takes place in the thylakoid membrane inside of chloroplast.
  • Light wavelengths transform to Adenosine triphosphate/ATP (chemical energy) and Nicotinamide Adenine Dinucleotide Phosphate/NADPH (reducing agent).
  • Photosystem 1 chlorophyll absorb light at a wavelength of 700 nanometers
  • Photosystem 2 chlorophyll absorb light at wavelength of 68O nanometers


  • Photolysis
    • Occurs in Photosystem 2 where water donates electrons (reducing agent) with light. The result of photolysis is oxygen (O2), hydrogen ion (H+, protons), and electron (e-).
    • Oxygen and hydrogen ions are transported into the thylakoid lumen.
    • Hydrogen ions are the catalyst to produce Adenosine triphosphate/ATP.
    • Oxygen is released as excess after photolysis.

2) Calvin Cycle

  • The second stage of photosynthesis occurs in the stroma of chloroplast.
  • Adenosine triphosphate/ATP (chemical energy) and electrons from Nicotinamide Adenine Dinucleotide Phosphate/NADPH (reducing agent) transform carbon dioxide into glucose and more.
  • Six carbon dioxide molecules (6CO2) are required to complete photosynthesis.
  • Six carbon dioxide molecules (6CO2) produce twelve Glyceraldehyde 3-phosphate (G3P’s).
  • Two Glyceraldehyde 3-phosphate (G3P’s) molecules produce one glucose.
  • Ten Glyceraldehyde 3-phosphate (G3P’s) molecules regenerate of


Ribulose Bisphosphate (RuBP).

  • Leaf
    • Upper and lower epidermis
      • Upper epidermis facilitates water transpiration/ sweating.
    • Plants sugars are synthesized with carbon dioxide and water.
      • The leaves have holes on the bottom called stomata.
      • Stomata
        • Absorb carbon dioxide
        • Release oxygen
        • Release water
        • When a plants releases water through the leaves it is called sweating
        • Humidity levels will rise in a garden due to plants sweating
      • Mesophyll
        • Photosynthetic/parenchyma cells contain chloroplasts.
  • Vascular bundle
    • Consists of xylem and phloem vessels transporting food, water, and dissolved minerals.



  • The unit of measurement for luminous flux is the
  • Measured based upon the sensitivity of the human eye.
  • One lumen is equal to one candela which is equal to one square radian (sr).
    • Square radian is also known as Steradian (sr).
      • A = r2
        • Is one square radian
        • “A” stands for area
        • “R” stands for radius
      • One lumen is equal to one lux per square meter.
    • The International System of Units uses the square radian to measure a solid angle.
      • Solid angle
        • The distance from a fixed central point, where two or more curves, edges, or lines meet (vertex), measuring the area of the light when projected in a direction.
      • 4π steradians is equal to a complete spheres solid angle.
      • At the distance of one meter one lumen per square meter is equal to one candela.
      • A light that equally disperses one candela in 360 degrees has a luminous flux of 12.57 lumens.


Wow, that’s a ton of information.  Are we more overwhelmed yet?  Are we having fun yet?  Ok, here’s the walk away.  Do not focus on watts.  Focus on lumens and the color rendering index when purchasing a light.  So, you read this article and want to purchase a light but it does not list lumens. Perfect.  No not really but here’s what we do.

Luminous flux ΦV in lumens (lm) =’s power P in watts (W), multiply luminous efficacy η in lumens per watt (lm/W):

Easy right!

ΦV(lm) = P(W) × η(lm/W)

Are you seriously still reading?

lumens = watts × (lumens per watt)

It’s tricky because some lights will not list the lumens per watt.  Please see images and charts for an idea.  The formula above shows us there is no easy take away to find lumens. Captain Sunshine uses a watts-to-lumens calculator available at or



  • Can be purchased as: Compact Fluorescent Lamp (CFL), T5, T8, T12
    • Fixtures can hold LED lights
  • Lights are daisy-chainable. Daisy chain means you can plug one light into another light so that when one is powered on so is the other.
  • Come in strips and panel arrays.
  • Lamps match the fixture output.
    • High Output (HO) or Very High Output (VHO)
  • Growth stage used in
    • Seedling, clone, pre-teen
  • T8 Coloring Render Index (CRI) range 75-98
  • Captain Sunshine started off using T5’s in order to keep costs low, scale was small to inspired hobbyist. Highly recommended for beginners and novices.
    • Benefits of florescent lights on the market is many come packaged with the bulbs, ballast, and reflector.
    • Florescent lights do not require cooling, such as using an Ice Box.
      • An Ice Box uses is used as a cooling source for High Intensity Discharge lights.
    • Florescent lights can be found for US$2 a tube.
      • Produce negligible heat meaning ventilation is less likely to be required unless your space is too small such as a closet.

Growth stage used in

  • Light spectrum shed by this type of lighting arrangement is well suited for literally all growth stages.
  • As fluorescents diffuse light onto a large area the lights will need to be 3 inches from the cannabis top/ canopy.
    • Not all cannabis is equal. Strains will respond differently to the proximity of lights.
      • When leaves are too close to a light the leaves will curl in towards itself.
      • This means you need to mount lights so you can comfortably raise and lower them as desired.
      • Captain Sunshine and friends use pulleys. Amazon has the best package deals for pulleys.  Captain Sunshine and friends prefer to support local business so we purchase as many of our products from our favorite local hydro store, nurseries, aquatic/ reefer stores because we believe in supporting our local communities jobs.


High Intensity Discharge

Known as double ended fixtures (DE)

    • Require ballast, reflector, and hood.
      • Modern light fixtures accept Ceramic Metal Halide bulbs as well as High Pressure Sodium bulbs.
      • Capable of producing lots of heat.
      • You will need fan(s), a powerful fan to make sure the room temperatures are down.
    • Technologies include: Ceramic Metal Halide (CMH) and High Pressure Sodium (HPS).
      • Ceramic Metal Halide (CMH) is often referred as Metal Halide (MH)
      • There are unfortunately many names in the market for Ceramic Metal Halide lights.
      • Also known as: Ceramic Discharge Lamp (CDL), Light Emitting Ceramic (LEC),
      • Ceramic Metal Halides use a ceramic arc tube
      • Metal Halide lamps are scientifically more accurate to the spectrum of the sun than High Pressure Sodium or Mercury Vapor lamps and Quartz Metal Halide lamps.
      • The industry standard is to produce Metal Halide tubes using ceramics.
      • Metal Halides Contains Ultra Violet radiation (UV)
        • Recommended for inspired hobbyists with money to spend, and experienced growers.
        • Ultra Violet radiation is a deterrent for pests, molds and quantitative evidence suggests Ultra Violet radiation promotes oil production, aroma, and taste.
        • Metal Halide technologies include Quartz Metal Halide (QMH), and Ceramic Metal Halides (CMH).
        • Ceramic Metal Halides are 10-30 percent more efficient on the light spectrum and lumen quality than Quart Metal Halides.
          • Quart Metal Halides have a Coloring Render Index (CRI) range of 65-70.
        • Ceramic Metal Halides have a Coloring Render Index (CRI) of 80-96.
          • Delivers the most scientific accuracy to the spectrum of the sun (until we invent something new).
          • Two times more efficient in the light spectrum than High Pressure Sodium.

Growth stage used in

  • Vegetative growth
    • Metal halides provide primarily the blue spectrum.

High Pressure Sodium (HPS)

  • Produces yellow / orange light that simulates fall equinox sun.
  • Growth stage used in
    • flowering
  • High Pressure Sodium and Metal Halide lamps are used by some gardeners as a team in order to moderate the light spectrum for the garden.
  • Coloring Render Index (CRI) range 22.


Light Emitting Diode

  • LED’s
  • Release electrons in the form of photons.
  • Emits light based upon the electric current.
  • More energy efficient for watts per lumen than incandescence
  • More energy efficient than High Intensity Discharge lights, yet offer less lumens
  • Some gardeners use Ultraviolet LED’s at a wavelength of 365 nanometers for the purpose of disinfection and sterilization
    • This is advanced.
  • More LED’s are coming into the market offering Ultraviolet B.
    • The team is currently experimenting with Ultraviolet B (UVB), yet it is not a controlled experiment. Looking forward to reporting in the future.
  • Induction light
    • Also known as an Induction lamp.
    • Captain Sunshine believes the market will eventually drive down the costs of these lights. However, these lights are for the expert growers or cash to spend inspired hobbyist.
    • Gardeners claim these lights will contribute to 20-40% greater Root Mass than all other technologies.
    • Gardeners claim these lights will contribute to 30% more internodes.
    • Gardeners claim these lights will contribute to the lowest carbon footprint for lights.
    • Captain Sunshine has not grown with these lights yet and looks forward to conducting a controlled experiment.
    • Growth stage used in.
      • vegetative growth, flower
    • Plasma(s)
      • Plasma types Light Emitting Plasma (LEP), Sulfur Plasma, LIFI
      • Higher efficiency than High Intensity Discharge for lamp life, depreciation, and output spectrum
      • Lacks cost effectiveness per unit and is recommended for experienced growers only or cash to spend inspired hobbyist.
      • Growth stage used in
        • vegetative growth, flower


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