Daylight & Full Spectrum Lighting Glossary

If you're new to the topic of full spectrum daylight bulbs, chances are that one could get easily confused with the different terms used such as Kelvin, Color Rendering Index and so on.

This is exactly why we made this small glossary for you - to easily find your way around the world of full spectrum lighting and to as quickly as possible know what to look out for. Here we go:


Siehe auch  Ballast

Base / Cap

This is the part of the lamp that connects into the light fitting, sometimes also reffered to as socket. Caps come in different shapes and sizes, to learn more check out this overview.

Bayonet (BC)

The BC stands for "Bayonet Cap" and basically means „push and twist“. It's most common in Australia, New Zealand, Ireland India, Cyprus and the UK. The standard B22 bayonet bulb is 22mm in diameter.

Beam Angle

Halogen spotlights come in different angles which is measured in degree (°). Smaller angles (eg. 10°) are particularly used to highlight single objects, whereas wider angles are used as general light source. The most popular wide flood beam angle is 36°.


A device for starting and regulating fluorescent and discharge lamps that limits the ultimate current to an appropriate level. Two types of ballast are available – magnetic and electronic. Older style magnetic ballasts (also called electromagnetic) typically contain copper windings on an iron core. Electronic ballasts contain electronic components, are smaller, more energy efficient and produce no lamp flicker.

Colour Rendering Index (CRI or RA)

An international method used to measure the quality of light and to rate a lamp's ability to render object colours. The higher the CRI the richer colours generally appear. The values range from 0 (worst) to 100 (sun light).
CRI ratings of various lamps may be compared, but a numerical comparison is only valid if the lamps are close in colour temperature.

Colour Temperature (CCT)

A measure of the colour of a light source relative to a black body at a particular temperature expressed in degrees Kelvin (K).
Lamps with colour temperatures below 5000K tend to be more yellow/red („warm“), lamps rated between 5000 and 6000K are viewed as white („cool“), while lamps above 6000K tend to have a blue cast. Cool-coloured light is considered better for visual tasks. Natural sunlight has a colour temperature of 5500 K (same as the Viva-Lite® Full Spectrum lamps).

Compact Fluorescent Lamp (CFL)

A type of fluorescent lamp that is single-ended and screws into a regular light bulb socket (eg. E27). In contrast to incandescent light bulbs, CFLs have a longer life and use less electricity.

Daylight Lamp

Typically used to describe lamps with a 6500K colour temperature rating. But because of the blueish light from these lamps colours tend to look washed out and dull compared to a true full spectrum light source. Daylight spectrum is also referred to by some companies as "balanced spectrum", "wide spectrum", "natural spectrum" and so forth but there is a significant difference between so-called "Daylight" and "Fullspectrum".

Dimmer (Dimming Control)

A device used to lower the light output of a source and thus vary the brightness of a light.
Fluorescent light fixtures cannot be connected to the same dimmer switch used for incandescent lamps.

Edison Screw (ES)

Developed by Thomas Edison in 1909. Used worldwide.
The standard E27 bulb is 27mm in diameter and used for all types of lighting.
The smaller E14 bulb (SES) is 14mm in diameter and particularly used for smaller decorative fittings, chandeliers, and appliance bulbs.

Electromagnetic field (EMF)

A physical field produced by electrically charged objects. Electromagnetic fields are invisible to the human eye but are naturally present everywhere. Man-made sources include cell phones, power lines, computers and anything electrical or electronic.
The potential effects of electromagnetic fields on human health vary widely depending on the frequency, intensity of the fields and the studies & research you read.

Electronic Ballast (EB)

Siehe auch  Colour Rendering Index (CRI or RA)

Energy Saving Lamp (ESL)

Like a Compact Fluorescent Lamp (CFL) - generally with an integrated Electronic Ballast.

Siehe auch  Daylight LampEnergy Saving Lamp (ESL)


Also called light flicker, refers to quick, repeated changes in light intensity. It is caused when the voltage supplied to a light source (mainly fluorescent lights) is unsteady or when the power line voltage itself fluctuates.
These fine but annoying changes can cause headaches, eye strain and concentation difficulties.
New electronic ballasts convert the flicker frequency to such a high level that the human eye cannot detect any fluctuation in the light intensity – and therefore feels at ease.
The use of high frequency electronic ballasts (minimum 20,000 Hz or higher up to around 50,000 Hz) in fluorescent lights may result in more than a 50% drop in complaints of eye strain and headaches.

Siehe auch  Colour Rendering Index (CRI or RA)

Fluorescent Lamp (FL)

A type of high efficiency lamp that uses electricity to excite low pressure mercury vapor in argon or neon gas, producing short-wave ultraviolet (UV) energy. This energy then causes a thin layer of phosphor on the inside of the glass tube to fluoresce which transforms invisible UV light to visible light.

Full Spectrum Lighting (FSL)

A term associated with light sources that produce a light spectrum that covers the entire range of visible light (380-700nm), parts of the UV spectrum (some UVA and very little B) without gaps in its spectral output, a colour temperature of approximately 5500 K and a minimum CRI of 91+

Siehe auch  What is Full Spectrum Light...

Halogen Lamp

An type of incandescent light bulb in which a tungsten filament is sealed into a compact transparent envelope filled with an inert gas, plus a small amount of halogen such as iodine or bromine. Halogen lamps get hotter than regular incandescent lamps because the heat is concentrated on a smaller envelope surface, and because the surface is closer to the filament. This high temperature is essential to their operation.

Halogen Spotlights

The most common halogen spots are either push fit (GU4 or GU5.3), low voltage type or twist and lock (GU10 or GZ10) mains versions. PLEASE NOTE the subtle difference between GU10 and GZ10. The GU10 has a bevel around the base but the GZ10 has a square corner. This stops the GZ10 being used in a fitting designed for a GU10 but allows the GU10 to be used in either. Spotlights operate under different voltages and should therefore be handled with care.

Incandescent Lamp

A source of electric light that works by incandescence. It consists of an outer glass bulb with a filament of tungsten wire inside, through which an electric current is passed. The bulb is filled with an inert gas (eg. argon) to reduce evaporation of the filament.
Incandescent light bulbs are gradually being replaced in many applications by fluorescent lamps, LEDs, and other devices for energy efficiency reasons. 
Some governments have passed laws and regulations that ban them completely.

Infrared (IR)

Infrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light (400-700 nm). Infrared is not visible to the human eye but can be felt as heat.

Kelvin (K)

The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero (0 K).
It is parallel to the Celsius (or Centigrade) scale. 0 C is 273.15 K.

Siehe auch  Compact Fluorescent Lamp (CFL)

Light Spectrum

Typically the portion of the electromagnetic spectrum that is visible to the human eye (380 nm to 750 nm), sometimes also called the optical spectrum or visual spectrum.

Light Therapy

Consists of exposure to daylight or to specific ranges of light wavelengths or very bright, full-spectrum light, for a prescribed amount of time (in some cases also at a specific time of day). Light therapy has proven effective in treating conditions such as seasonal affective disorder (SAD), depression, sleeping disorders, skin diseases (acne vulgars and psoriasis), neonatal jaundice and jet lag.
Light therapy is also called phototherapy.

Siehe auch  Premenstrual Syndrome (PMS)

Lumen (lm)

A measure of the luminous flux or quantity of light emitted by a source. For example, a candle provides about 10 lm, whereas a Viva-Lite® T8 36W tube currently provides 2300 lm.
Lumen can be used to measure light bulbs as stand alone light sources while lighting fixtures are measured by lux ouput which is lumens per square meter.

Lux (lx)

A unit of illuminance or light falling onto a surface. Typically used to measure the light intensity produced by a lighting fixture. The higher the lux reading the more light the lighting fixture is producing over a given area. One lux is equal to one lumen per square metre.


A hormone derived from serotonin and naturally produced by the pineal gland. It plays a role in sleep, aging, and reproduction and is important in the regulation of the circadian rhythms. Production of melatonin is inhibited by light and permitted by darkness.

Nanometre (nm)

Used to measure the wavelengths of light. One nanometre is equal to one billionth of a meter. The lower the wavelength eg. 400nm the more blue and stronger the light source. Longer wavelengths such as 700nm are red and contain less energy.

Neodymium Lamp

An incandescent lamp containing neodymium (an earth element) in the glass to filter out yellow and red light, resulting in a whiter light more like sunlight.

Phosphor (Phosphorus)

An inorganic chemical compound processed into a powder and deposited on the inner glass surface of fluorescent tubes and bulbs. Phosphors are designed to absorb short wavelength ultraviolet radiation and to transform and emit it as visible light. Ordinary fluorescent lamps use two to three phosphors while full spectrum lamps use a minimum of five phosphors.


Siehe auch  Lumen (lm)

Premenstrual Syndrome (PMS)

Physical, psychological, and emotional symptoms such as irritability, food cravings, tension, abdominal cramps and headache that are related to a woman's menstrual cycle. Generally, symptoms vanish just before or after the start of menstrual flow.
Light therapy can help alleviate the symptoms of PMS in some women due to the connection between serotonin and changes in visible light.
Premenstrual Dysphoric Disorder (PMDD) is the more severe version of PMS and may also benefit  from light therapy.

Seasonal Affective Disorder (SAD)

Also known as winter depression or winter blues, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter.
There are many different treatments for SAD, including light therapies, medication and icognitive-behavioral therapy.

Spectral Chart

A chart showing the relative spectral output of a lamp or light source.

Spectral Glasses

Specially designed prism glasses where the white light is dispersed into the colours of the optical spectrum (rainbow colours).

Siehe auch  spectral glasses in the online shop...


Siehe auch  Light Therapy


A fluorescent lamp that is five-eighths of an inch (16 mm) in diameter. These lamps are among the newest form of fluorescent lamps with energy efficient high light output characteristics. Tend to create more heat and have a shorter lifespan than other fluorescent lamps. Require an electronic ballast to operate.

Siehe auch  Energy Saving Lamp (ESL)Full Spectrum Lighting (FSL)


A fluorescent lamp that is eight-eighths of an inch (26 mm) in diameter. These lamps are more energy efficient than the older T12 lamps but do not have the lumen output that newer T5 lamps produce. Require an electronic ballast to operate.

Siehe auch  Energy Saving Lamp (ESL)Full Spectrum Lighting (FSL)


A fluorescent lamp that is twelve-eighths of an inch (35 mm) in diameter. These lamps were very common until the mid 1990s when more energy efficient T8 and now T5 where introduced.

Siehe auch  Full Spectrum Lighting (FSL)


Although the invention of tri-phosphor lamps can be seen as a real improvement compared to older standard fluorescent tubes, they only use three phosphors instead of minimum five used by full spectrum lights. Triphosphor lamps usually achieve a CRI of maximum 85.

Siehe auch  Phototherapy

Ultraviolet Light (UV)

The portion of the electromagnetic spectrum with wavelengths shorter than that of visible light, but longer than x-rays, in the range of about 100 to 380 nm. The name derives from the fact that UV light has frequencies higher („ultra“) than those that humans identify as the colour violet.
UV light is found in sunlight and has many effects, both beneficial (vitamin D) and damaging (sunburn), on human health.
UV light is typically broken into three parts, UV-A, UV-B, and UV-C.

Siehe auch  Visible SpectrumUV-C (280–100 nm)UV-B (315–280 nm)

UV-A (380–315 nm)

Also called Long Wave or "black light" because it is invisible to the human eye. Can cause skin irritation and fading of fabrics. Does not cause sunburn but penetrates deeply and new studies show that it can even repair damaged skin.

UV-B (315–280 nm)

Also called Medium Wave. Can cause sunburn and other damage to the skin and human eye.

UV-C (280–100 nm)

Also called Short Wave or "germicidal" for its ability to destroy even bacterial life forms. Screened out by ozone layer.

Visible Spectrum

Siehe auch  Light Therapy

Vitamin D

Vitamin D is a fat-soluble vitamin derived from foods (only few) and sunlight. Its synthesis in the human body is triggered by sun exposure (especially UV-B rays) to the skin. Vitamin D plays an important role not only for bones and teeth but also in the prevention of diabetes, cancer and heart attacks.

Volt (V)

The unit of "electrical pressure" = electromotive force (voltage) between two points. The higher the voltage, the more current will be pushed through a resistor connected across the points.

Watt (W)

The unit for measuring an amount of power, especially electric power. Lamps are rated in watts to indicate the rate at which they consume energy when in operation. The energy cost of operating an electrical device is calculated as its wattage times the hours of use.

Winter Blues

Typically used to describe the symtoms associated with SAD such as feelings of sadness and lethargy, increased appetite and increased sleepiness. Can be treated with light therapy.

Siehe auch  Spectral Chart

PL-L = Long version

Siehe auch  Daylight Lamp

PL-S = Short version

Siehe auch  Daylight Lamp

PL-C = Carré (4 legs)

Siehe auch  Daylight Lamp

PL-T = Triple (3x2 legs)

Siehe auch  Daylight Lamp

PL-Q = Quadrant shaped

Siehe auch  Daylight Lamp

PL-R = Radius model (relating to the round socket)

Siehe auch  Daylight Lamp

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