I don’t mean to be critical of the site for propagating slightly inaccurate information because the post is very good information for the amateur photographer, however I believe that they oversimplify and repeat some misconceptions about light color that serve only to obfuscate one of the most fundamental aspects of image capture.  Camera manufacturers are somewhat complicit in this simplification of lighting color by using Kelvin numbers as white balance settings, but it’s important to remember that “Color Temperature”, “Color Balance” and “White Balance” are all different things.

As the article states (emphasis included from the original post):

“Light comes in a variety of colors. It’s not just “white”. Tungsten light bulbs, for example, are yellow/orange in color. Fluorescent bulbs are somewhat green. Daylight is blue. We know this is the case because of how these types of light reflect off a white surface… and we call this color cast the color temperature of the light.”

Color Temperature is essentially a shorthand measurement of spectral radience based on Planck’s Law.  Although it’s used to describe nearly all light, the color temperature scale relates only to incandescent sources.  Arc and gas discharge sources like fluorescent, sodium vapor and HMIs do not incandesce and the color temperature scale does not apply to their illumination.  A Correlated Color Temperature, used for non-incandescent sources, is generally used in the same descriptive terms as traditional Color Temperature (though as I note in this post, the color rendering of each lamp can be widely divergent from incandescent sources).

What’s confusing in understanding Color Temperature is that it’s a measurement of the emission of light, NOT the reflection of light as the article suggests.  Color balance and white balance are electronic adjustments performed to the captured measurements of reflected light intended to achieve a perceptually neutral image. 

In this sense, white balance CAN be described as the color of light reflecting off a white surface, however Color Temperature cannot be described the same way.  Furthermore, in many situations, adjusting a neutral white point can still leave color casts in neutral mid-tones which affect color balance.  In an 8-bit colorspace, there are only 256 values per channel to describe a color,  providing a very tiny range of adjustment when limited to the white values of an image.  This simplification of white balance as an overall color balancing tool can lead one to believe inaccurately that in-camera white point adjustments will reliably result in balanced color across the entire range of tones.  In practice, measured adjustments of neutral black, mid-tone grey and white points will often be needed to produce a truly neutral image.

In summation: 

• Color Temperature is a descriptive term relating to the emission of a given light source.
• White Point/White Balance is an electronic adjustment of RGB values to neutralize the light reflected from a white surface within an image.
• Color Balance is the overall neutrality of an image exhibited by neutral values in pure black, mid-range grey and white points of a given image.

Intertwined, yes, but all different concepts. 

For a much better explanation of basic color temperature, I’d read this article here.

Since I’ve challenged myself to try and create a lighting solution similar to the Lowel Ego light, understanding some basic fundimentals of fluorescent light will greatly help in choosing an “off the shelf” system that will produce optimal results.

The color of visible white light is commonly described using a standard of Color Temperature measured in degrees over the Kelvin scale.  In photography, we are generally divide light into the two ranges of “Tungsten” at 3200° Kelvin and “Daylight” at around 5600° Kelvin, but since those measurements only apply to incandescent lighting, all too often the concepts of the Color Temperature scale are not fully understood.  At it’s basic level, color temperature is exactly as the name describes: color of the electromagnetic radiation (light) similar to that emitted by a pure black object heated to a given temperature.

Color | Temperature.

Woah, woah, woah…what’s this black body?

Well, in physics, they visualize color temperature through heating a “theoretical” black body radiator.  If you want to go steady with a physicist, I’d that you read up on Planck’s Law, but if you’re an average Joe like me, I’d suggest that you just try and absorb these CliffsNotes.  I say “theoretical” because this object does not actually exist, it’s an ideal form of matter that absorbs all electromagnetic radiation and reflects nothing.  When this black body is heated it gradually begins to emit thermal radiation.  As the temperature of the body increases, that object begins to incandesce, emitting radiation as visible light. 

An instant analogy are the coils you see in any electric oven, space heater, or toaster: at room temperature, the coils appear close to black, but as they heat up they become incandescent, emitting some of that thermal radiation as a warm red light.  For an ideal black body radiator, as the temperature reaches 3200° Kelvin, the light that is emitted is visually similar to the color of light emitted by a photographic quality tungsten-quartz lamp. As that temperature approaches 5600° Kelvin it emits light similar to average daylight.  So, the color temperature scale is a relative or comparative scale that indicates the visual similarities between this black body radiator and a given light source. 

Why is this important when considering fluorescent lights for photography?  Well, it’s important because fluorescents are NOT incandescent lights.  Unlike tungsten lighting, there is no solid filament within them that is being heated to produce illumination through incandescence.

Since Color Temperature is the measured color of incandescence, it does not apply to discharge illumination sources such as fluorescent lights.

Wait, what?  Yes, that’s right.  If you see a specific color temperature on the packaging a fluorescent light, you can be assured that the measurement is a lie. 

Next, we’ll start to explore the magic of the Correlated Color Temperature (CCT).

**I updated this post this morning to correct a few spelling errors and add in wikipedia links.  I’ll try a to have a little less vodka before posting next time**