Joel Cummins
- May 15, 2018
- 4 min read

Lighting 101

This is an outline of the terms and descriptions lighting people throw around all the time. Some of these are my own interpretation, some are scientific (with links for digging deeper). There is a vast amount of data available, this list is aimed at simplifying it all.

Circadian Rhythm: Circadian rhythms are physical, mental, and behavioral changes that follow a daily cycle. They respond primarily to light and darkness in an organism's environment. Sleeping at night and being awake during the day is an example of a light-related circadian rhythm.

Credit: National Institute of General Medical Sciences

Visual representation:

Credit: Yasine Mrabet

References:

https://www.nigms.nih.gov/education/pages/Factsheet_CircadianRhythms.aspx

https://sleepfoundation.org/sleep-topics/what-circadian-rhythm

Color Shift: The transition of a light's color across a span of time. Intentional Color Shift changes from warm to cool and back to warm to mimic the sun's color throughout the day creating a natural lighting feel indoors. Unwanted color shift occurs when light sources degrade with age and appear dissimilar to other surrounding lights.

Color Temperature: On a scale of 1K to 10K (K=1000 degrees kelvin) 1K is orange and 10K is blue. Lower numbers are generally referred to as "Warm" and midrange numbers as "Cool" and higher numbers as "Daylight". For reference think of the Sun at noon (5000 kelvin) as the middle of the scale. The color of the sky in Vail (10,000 kelvin), a cloud covered sky (6000 kelvin), an incandescent light bulb (2800 kelvin) or a candle (1900 Kelvin). In lighting, We tend to like warmer tones in residential and cooler tones in workspaces. These variations can affect productivity and sleep cycles (See Circadian Rhythm).

Color Temperature Visualized:

Credit: Green Efficient Living

References:

https://www.lumens.com/how-tos-and-advice/kelvin-color-temperature.html

https://www.olympus-lifescience.com/en/microscope-resource/primer/lightandcolor/colortemp/

CRI (color rendering index): According to the Lighting Research Center- "In general terms, CRI is a measure of a light source's ability to show object colors "realistically" or "naturally" compared to a familiar reference source, either incandescent light or daylight."

Credit: Lighting Research Institue

Sample:

Photo Credit: http://www.digiolighting.com/cri/

The image above represents low CRI and poor color rendering in the top half, and high CRI and good color rendering at the bottom.

A lamp or fixture will typically have a CRI number, the higher the number the better the quality of light. 90+ is very good. Fluorescent lights usually have miserable CRI and do not render colors very well making things look greenish-blue (this is not flattering). Early generation LEDs also suffered in this area and would ofter make everything look yellow.

Another measure of color accuracy is TM-30. While this may be a more complete approach it is not as commonly used at the time of this post. If you want to dig- check out https://alphabetlighting.com/tech-tm30

References:

http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/lightsources/whatisColorRenderingIndex.asp

Digitally Addressable Fixture: A digitally addressable fixture exists as a departure from conventional wiring and control. Instead of having 6 recessed cans wired to a dimmer for example, these fixture have a source of constant power and a communication wire, each fixture is manufactured with intelligence so that fixture performance is maximized, fixtures can be controlled individually or as zones of light together with multiple fixtures. Dedicated LED engines provide higher lumen output, color shifting, and superior dimming than their conventional predecessors. Stand-alone addressable lamps like Philips Hue create a personal wireless lighting system. For new construction- Lutron's Ecosystem digitally addressable fixture technology provides industry best capabilities without clogging your home's WIFI network. These systems offer never before seen flexibility and LED performance. Ecosystem technology is available in hundreds of fixtures built by many of the worlds leading brands.

Reference:

http://www.lutron.com/en-US/Products/Pages/LightingFixtures/LutronFixtures/FinireCategoryPage.aspx

https://www2.meethue.com/en-us

Light, Fluorescent: Efficient, poor light quality, dims badly, difficult to dispose of. (you guessed it... I am not a fan) this technology is on the way out.

Reference: (if your kid needs to do a report for school)

http://www.edisontechcenter.org/Fluorescent.html

Light, Incandescent: The original "Edison" designed light bulb, incandescent light is the industry standard since it's introduction in 1879. They contain a tungsten filament that glows brightly when electricity is applied in a vacuum.These lamps are being phased out by federal mandate (2012) in favor of more efficient light sources (namely LED)

Reference:

https://www.sylvania.com/en-us/products/incandescent/Pages/default.aspx

Light, LED (light emitting diode): LED lighting products produce light approximately 90% more efficiently than incandescent light bulbs. How do they work? An electrical current passes through a microchip, which illuminates the tiny light sources we call LEDs and the result is visible light. To prevent performance issues, the heat LEDs produce is absorbed into a heat sink.

Credit: Engerystar.gov

For our purposes LED light is fast becoming the standard light source for almost all applications. Even the concept of "screw-in" replaceable lamps is disappearing as manufacturers across lighting industries are producing fixtures with dedicated LED modules native to their products.

What is most exciting about this technology is the introduction of color shifting LED and digitally addressable fixtures (also described on this page). These features are creating truly customizable light that will change throughout your day to meet your needs every step of the way.

LED retrofit lamps like the Soraa MR-16s below are available to replace their incandescent predecessors.

Reference:

https://www.energystar.gov/products/lighting_fans/light_bulbs/learn_about_led_bulbs

https://www.soraa.com

Light, Natural: Natural light exists in few forms, stars (like our sun) produce the lion's share of our natural light. Moonlight reflects the sun's light back to us at night. Fire produces natural light. Anheuser-Busch makes Natural Light- an inexpensive and not very good light beer in a can., it is my dad's favorite.

Lumens: Simply put, a lumen is a measurement of light delivered. As a baseline, a 60 watt incandescent light bulb (like the one pictured above) delivers roughly 800 lumens. There are various metrics for measuring light output: Lux, foot-candles, candle power, radiance, but the one most commonly used in labeling is definitely LUMENS. See "reference" for the science. If you ask the question,"How many lumens do I need?" this may more broadly evaluated by lighting professionals as there are numerous factors: What task are we lighting? Is the space full of dark surfaces like stone or stained wood? How high are the light sources? 1000 lumens can seem like a lit match in a very high ceiling surrounded by dark walls and floor. 1000 lumens can also be blinding if it's right in your face.

Lumens are not watts; watts are energy (electricity) used. Lumens are light output. LEDs use far fewer watts than incandescent lights to produce equivalent light output (lumens).