Fluorescent lighting has become ubiquitous in our daily lives as an energy-efficient and cost-effective lighting solution, but that familiarity can lead one to believe incorrectly that fluorescent light is interchangeable with other common sources.  The truth that both pure sunlight and electric incandescent lighting are fundimentally different from fluorescents, and to completely understand the potential pitfalls of fluorescent lighting, one must come to understand the basis of these differences.

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**