by Eric Strandberg LC, Lighting Design Lab
As a lighting consultant I often hear people say, "I hate fluorescent". Have you ever said it?
Many of us think of cold, institutional spaces when we think of fluorescent (FL) lighting. This is because of
- the poor color qualities of the old style lamps (T-12),
- the noise and flicker from magnetic ballasts
- the indifferent lighting design applied to many commercial spaces.
Justifiably, we object to buzzing ballasts, flickering lamps, and poor color quality.
Today's fluorescent products (T-8 lamps with electronic ballasts) can solve of these problems… except indifferent design.
Color quality of light has two parts.
The most obvious is color temperature, this is whether
the light appears 'warm' or 'cool'. Color temperature is expressed in Kelvins
(a scientific scale) with 3000K being similar to incandescent (yellow/warm)
and 5000K being similar to sunlight (blue/cool). FL lamps come in these and
other color temperatures. Which one you choose is subjective, like paint colors.
Today, the most popular color temperature is 3500K, not too cool, not too
warm. This color is often preferred for retail, office and high activity residential
spaces. (I use it above my drafting table at home).
The other part of light quality is color rendering, this is the ability of a light source to reveal the "true" relationship between colors. Light sources with poor color rendering cloud the difference between similar colors. For example a slate green wall may appear to be the same color as a gray blue wall, or dark amber paint may look the same as light brick. Color rendering is expressed numerically on the color rendering index (CRI), which is a scale from 0 to 100, with higher values being better. Most old style FL lamps have poor color rendering (50 - 60) which makes people and surfaces look unfavorable (dull colors & gray complexions). The newer FLs have a very good CRI (from around 75 up to as high as the 90s), which reveal colors very accurately.
Flickering lamps and buzzing ballasts are legitimate problems that
can both be solved. All FLs use a ballast, (an electrical device) to operate
the lamp. Historically these ballasts have been magnetic devices, (core &
coil), that operate at 60 cycles per second, which some people perceive as
flicker. Also, the magnetic ballast can physically vibrate which causes an
audible buzzing or hum.
Electronic ballasts, (solid state), operate at 24,000 cycles per second and
higher, eliminating the flicker completely. Also, with electronic ballasts
there is no blinking when the lamps are being lit, they just turn right on.
This is not a big factor commercially since the fixtures tend to stay on all
day but in peoples homes the lack of blinking can go a long way toward acceptance.
Also, because the new electronic ballasts are solid state there is no audible
hum or buzz.
Because they are large radiant tubes, FL lamps are good at providing general or ambient light, and evenly washing large architectural planes (walls and coves). An abundance of even, shadowless light is just what we want in many spaces like kitchens, home offices, and workshops. Appropriately applying fluorescent lighting in living or dining areas where more drama and atmosphere is usually wanted can be a challenge. Indirect cove lighting, luminous soffits, and light shelves are all ways of creatively using linear fluorescent lighting in living areas.
If the heart of a lighting system is the light source then the body and soul is the light fixture and the designer's artful use of it. Knowing how to get a proper balance of ambient, task and accent light in our work and living spaces is part of the designer's art. Often, when we criticize poor lighting it is really bad or indifferent lighting design as much as bad light sources that we object to.
