Lamp Science


Lamp Anatomy

HID (High intensity Discharge) lamps are a type of electrical gas-discharge lamp which produces light by means of an electric arc between tungsten electrodes. These electrodes are housed inside a transparent fused quartz or translucent fused alumina arc tube. These lamps produce a high amount of photons per amount of energy input (watt) and are the primary type of artificial light source used to support plant growth.

Sunmaster lamps are designed  specifically for horticulture purposes and manufactured using ISO 9001 processes.

1. Boroilicate Outer Envelope – protects arc tube, filters harmful UV
2. Mechanical Support – supports and positions Arc Tube
3. Barium Peroxide ‘Getter’ – removes impurities to provide long lamp life and proper performance
4. Alumina Oxide Coating – a thermal insulator to keep the ends of the arc tube warm, keeping halides in the arc stream
5. Quartz Arc Tube – houses unique Sunmaster chemical compound, electrodes and filled to a precise pressure
6. Mica Heat Shield – thermally insulates the base end of the lamp
7. Base – provides electrical interface with socket to ballast
8. Ceramic Insulator – Isolates the electrical contacts
9. Halide Pool (appears to be a lamp defect) – Unique blend of metal salts that modify lamp spectrum and aid in lamp life
10. Doped’ Quartz Outer Envelope – protects arc tube, filters harmful UV
11. Mechanical Support – supports and positions Arc Tube
12. Button ‘Getter’ – removes impurities to provide long lamp life and proper performance
13. Ceramic Arc Tube – houses amalgams, electrodes and filled to a precise pressure
14. Molybdenum Foil – provides electrical connection while supporting hermetically sealed quartz envelope
15. Lead – provides electrical interface with socket to ballast

Photons & Wavelength

 Light is energy and, simply put, nature’s way of transferring energy through space. A photon is a particle representing a quantum of light or other electromagnetic radiation. Not all photons are created equal, at least in terms of how much energy they contain. A photon carries energy proportional to the radiation frequency, or distance between wavelengths.  Therefore a photon in the blue wavelength has a different energy level than a photon in the red wavelength.

Lumens / CRI / CCT

 Lumens, Color Rendering Index (CRI) and Correlated Color Temperature (CCT) are common terminology used to describe general lighting output but are not nearly as significant in reference to plant growth. Sunmaster coined the phrase ‘Lumens are for Humans’ years ago just for that reason! Even so, some lamp brands marketed to the horticultural industry still advertise lumens, CRI and CCT which, especially in relation to general lighting applications, mean the following:

Lumens is a measurement of light output that basically relates to brightness. It refers to a unit of luminous flux that is equal to the amount of light given out per second by a uniform source of one candela radiating equally in all directions. Historically, lumens have been used as an indicator for a lamps’ ability to grow plants, meaning the brighter the lamp, the better the lamp was for growing plants. However, numerous studies have shown that lamps with color spectrum tailored to the needs of plants, or even specific genus or species of plants, will perform much better than a lamp that simply has high lumen output. Luminous flux, which is a photometric quantity, represents the light power of a source as perceived by the human eye, which has a peak sensitivity in the yellow-green region (around 550 nanometers, or the “optic yellow” color used for highly visible signs and objects). The unit of luminous flux is the lumen. Technically, a monochromatic light source emitting an optical power of (1/683) watt at 555 nanometers has a luminous flux of 1 lumen. Since the human eye is more sensitive to light in the green wavelength, more weight has been given to ‘green’ than other areas of the visible spectrum when calculating ‘lumens’. Therefore, lumens have become an antiquated method to fairly determine an artificial light source’s ability to grow plants.

Color Rendering Index (CRI) is a subjective measurement of how well a light source renders colors. More technically, CRI is a measurement of the degree of color shift an object undergoes when illuminated by a light source when compared to a reference source of comparable color temperature.

  • Incandescent light is assumed to have a CRI of around 100 so it will render all colors correctly.
  •  Metal Halide lamps typically have a CRI of about 70. Certain Sunmaster lamps such as the ‘Full Nova’ family employ special chemical doses that significantly  broaden the lamps’ spectrum with some surpassing 90 CRI.
  • HPS lamps typically emit a CRI of about 22.

While CRI is an indicator of how balanced a spectrum is, CRI alone is not a fair parameter to measure a light source’s ability to provide energy in the proper wavelengths for plant growth (see PAR below).

Correlated Color Temperature (CCT) is the relative white quality of a piece of tungsten steel heated to that temperature in degrees Kelvin. HPS has a warm (red) color temperature of around 2700K as compared to that of a typical metal halide lamp (4,000K to 10,000K), which has a cooler (blue) color temperature. CCT represents the combined spectral output of a lamp and provides a picture of the exact wavelengths and strengths of each wavelength that has been combined to create the CCT.

Sunmaster FULL NOVA spectral output

As an example, a full spectrum lamp such as Sunmaster’s FULL NOVA family, has a CCT of approximately 6000K while a cool spectrum lamp such as Sunmaster’s COOL family, has a CCT of approximately 5500K. So, while the light output of these lamps differs by only ~500K, the spectral qualities of these lamps are much different. Therefore, CCT is not the best measurement criteria to determine a light source’s effect on plant growth.


Sunmaster’s COOL spectral output

Lamp Life

Lamp life is an important consideration when purchasing lamps. Two very different and distinct terms describe life: “rated life” and “economic life”.

Rated Life

Rated life for HID lamps is a value of lamp life expectancy based upon laboratory and field tests of representative lamps, operating on approved ballasts, with a burn cycle of at least 10 hours per start. The lamp life is determined when 50% of HID lamps initially installed are still operating.

 Economic Life

Economic life refers to the hours of operation during which a lamp is designed to provide optimum light output and color quality as well as lowest replacement cost. Economic life describes actual lamp life better than rated life because rated life does not account for the lumen depreciation and color shift that occur as lamps age. The economic life of lamps is generally 60% to 75% of the lamp rated life. Though economic life is important when considering a lighting system, lamp data tables show rated life because they provide a standard comparison with other lamp manufacturer’s ratings.


Lamp Spectrum

 Lamp spectrum is heavily dictated by the specific technology behind each lamp family (ie metal halide, CMH, HPS). For discharge lamps, spectrum can be modified via different methods within each of these product families. Optimizing spectrum for specific plants or for specific growth phases is critical to the performance of artificial light sources.

  • Metal Halide  – Spectrum can be heavily modified by adding various halide salts
  • High Pressure Sodium – The ability to alter spectrum in HPS lamps is somewhat limited but can be accomplished through the  amalgam within the arc tube as well as the arc tube fill pressure  and geometry
  • Ceramic Metal Halide – Typical CMH lamps have a broad spectrum
  • Target = focus the energy where plants need it


 Photometry is the science of the measurement of light, weighted in terms of perceived brightness to the human eye.  The measurement of light sources (e.g. lamps and LED diodes’) is typically conducted within an integrating sphere.  While most integrating spheres output data in general lighting terms (lumens, CRI, CCT, etc.), mathematical functions can be applied to properly convert this data into measurables related to plant growth (µmole/sec, PPF, YPF, etc.)

Not all integrating spheres are created the same, nor do various users utilize this  type of equipment in the same fashion.  Venture Lighting, Sunmaster’s parent company, owns and operates spheres that are calibrated to National Institute Standards (NIST).   All sphere data is properly converted to plant growth measurable data (µmole/sec, PPF, YPF) according to International Commission on Illumination (CIE) standards.

Matching Lamp to Ballast

 SUNMASTER grow lamps are HID lamps. This means that for each lamp to operate it must use the coordinating ANSI code ballast, as designed and assigned by the American National Standards Institute.  The key to HID lighting is the synergy of the lamp and ballast system, which offers a much higher efficacy (or total system efficiency). If you have questions, feel free to contact SUNMASTER for more information about achieving the best lighting for growing.




High intensity discharge lamps are currently the artificial light source of choice for over ninety percent of the horticultural market.   That being said, Light Emitting Diodes (LEDs) are increasingly becoming more efficient as well as being optimized to supply the precise spectrum needed for various types and stages of plant growth.   Sunmaster recognizes that, as LED technology continues to advance, they will have an increasing role within the plant growth market.  As such, while Sunmaster continues to optimize /advance HID lamp sources, the company is in the process of designing/developing new products incorporating LEDs.

HID Strengths

  • High PAR values as measured in µmol/sec
  • Good for lighting large spaces
  • Ability to tailor spectrum for specific plant needs
  • Lowest cost solution

LED Strengths

  • Specific wavelength, if desired
  • Options to provide selective wavelengths
    (deep blue or red)
  • Low heat, allowing light source to be in close
    proximity to plants
  • Good for early vegetation period or for herbs
    and vegetation