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Compact Fluorescent Light Bulbs!  (CFLs) 

Imagine that we are at Home Depot shopping for light bulbs!  The aisle stretches the full width of the store with a dizzying array of incandescents, halogens, CFLs and LEDs.  Once again we have to expand our vocabulary in the new jargon on light bulbs.  Today we will simply focus on CFLs and try to unravel the mystery of lumens, kelvins, CRIs, foot candles and color temperatures.  

Fully armed with our keyword, lumens, we have already stepped out of our comfort zone and are now looking for:  800 (75W) 1000 (100W) 400 (60W) 200 (40W) 100 (25W) lumens.  These are approximations since the manufacturers have been introducing energy efficient incandescents with higher light output for similar usage of electricity.  Thus if you start looking at GE’s Reveal and Philips Eco Advantage, you will simply be adding to the confusion.  Best therefore, once again, adjust your needs to lumens, and you can’t go wrong. By the way, did you know that there are also standard sizes for light bulbs with designations A19 (for the most common) A15 (somewhat smaller) and A21 (bigger), which will begin to matter for fitting a bulb into specific types of lamps.   

So far many consumers are not happy with CFLs for a number of good reasons: the light is too harsh, not bright enough, slow to light up, incompatible with dimmer switches and dangerous because of the mercury they contain. Manufacturers have started to address these issues resulting in a large selection of CFLs.  To make the proper choice, we need to learn a few more keywords.  

Our next keyword is color temperature which is expressed in degrees Kelvin (K) on light bulb labels.  Color temperature is a description of the warmth or coolness of a light source, but it is not an indicator of lamp heat. 

2700K CFLs produce a warm yellowish light, similar to that of incandescent bulbs.  They are good for rooms featuring amber or mahogany colors.  Warm light is preferred for living spaces because it is more flattering to skin tones and clothing.
3500K CFLs make rooms with bright reds or greens look their best. 
4100K CFLs make rooms with lots of birch or bleached wood look great.  Cool light is preferred for visual tasks because it produces higher contrast than warm light.
5000K CFLs (and 6500K) produce a bright light similar to daylight – particularly appropriate for rooms full of grays or slate.  There is some concern that they could interfere with sleep cycles more than bulbs lower on the color temperature scale.  Therefore, consider not using these bulbs near bedtime or in bedrooms if you have trouble falling asleep.   

In addition to color temperature we must consider the color rendering index (CRI) describing a light sources ability to accurately render the colors of people and things.  CRI is measured on a scale from 0 to 100.  The higher the CRI, the better the lamp will make things appear with a better visual perception of colors.

90 CRI 5000 K for an artist’s studio would render colors most accurately.
70 CRI 3000K, a light which is visually warmer would soften contours and surfaces and is appropriate for a kitchen and bath.  The lower CRI would shield people and food from too harsh an appearance.   

Bulb shape.  Most consumers don’t like the look of spiral-shaped CFLs, and they don’t work with clip-on lamp shades.  Therefore, bulb makers now offer a variety of cone-shaped bulbs that are also available for recessed fixtures and flood lights.    

Dimming ability is crucial if we want to adjust our ambient lighting.  CFLs are not dimmable unless the packaging tells you so.  To be compliant with the new regulations (once they are in effect), we need to replace our dimmer switches with new ones that are designed to be compatible with CFLs and LEDs. 

To complete our survey of light sources and measurement, we would like to mention footcandles (fc), which measure the light level of surfaces and reflections.  With a light meter as we used before automatic cameras and which is still the tool of professional photographers, we can take readings that will give us the following guidelines:

Outdoor light at noon                         summer 10,000 fc                winter 1,000 fc
Gathering rooms & hallsways                            25 fc
Bedrooms                                                                  12 fc
Kitchen and bathroom                                         50 fc
Task lighting                                                            50-100 fc  

Sort Through the Light Bulb Array
With Help from Pyramid Feng Shui!