Mar 2013

Light Sources Part II – Fluorescent & CFL

Fluorescent lighting has gotten a bad reputation over the years because lots of people associate fluorescent lighting with flicker, bad CRI and cold color temperature. All that is valid because fluorescent lighting had all those qualities a few years ago. But most of today’s higher quality  fluorescent tubes and CFL’s have overcome all those problems. They use better ballasts to prevent the flicker and they use good phosphors to improve both CRI and color temperature.

Fluorescent lighting is almost as efficient as LED and it is about 4 time mores efficient than incandescent lighting. One drawback is the mercury that fluorescent light bulbs contain. Another drawback to fluorescent lighting is that it can not be dimmed as easily as LED or incandescent, but there are dimmable ballasts available for both CFL and tubular fluorescent light bulbs.

A typical CFL.

All fluorescent light bulbs are a hollow glass tube which is coated on the inside with a rare earth phosphor and filled with a gas that contains mercury. Fluorescent light bulbs have a ballast, either integral to the light bulb or enclosed in the fixture, which converts AC current to high frequency and applies that current to the glass tube. The current excites the gas in the tube which causes the phosphor coating the inside of the glass to glow. The quality of the light is directly related to the quality of the phosphor. Cheap phosphors result in poor CRI and bad color temperatures whereas more expensive phosphors produce pleasing high CRI light. There is a reason good quality is more expensive.

Pictured here are two different CFL’s
and two sizes of fluorescent tubes.

CFL’s have become more commonplace over the past few years. Some fit into regular screw-in sockets and some have dedicated sockets with different pin configurations. Most of the ones that screw in have their own ballast while the ones with the pins rely on the ballast in the fixture. More and more fixture manufacturers are producing fixtures that require the pin base because they meet the Government’s requirements for energy efficiency and also meet standards for LEED certification.

Fluorescent is a great light source and is much more affordable than LED. It is not recommended for use in exterior fixtures in cold climates because it takes a few minutes for fluorescent lights to warm up to full output on a really cold day.