Cheers

John

Lawrence

When I built my Upper Peninsula “Workshop in the Woods” I placed both incandescent and electronic ballast T-8 fixtures on the ceiling. This elevates the CRI in the shop, and frankly I feel that this is the most important index for woodworking shops, especially if colors of finishes are to be seen true.

I also followed Henry Ford’s advice, “You can paint your shop any color as long as it’s white”. (At least I think he said something like this) Regardless, white walls and ceiling really help to reflect light and reduce shadows.

Ralph

Regarding output, I’m not aware of a problem with the lumen outputs marked on CFL bulbs, though it doesn’t address dimming over time. But the so-called equivalencies are bunk. A standard single life 100W bulb generates 1700 lumens and yet you’ll see CFLs marked as “100 W equivalent” that only produce 1500 lumens, or less. If you compare lumen output directly and ignore any alleged wattage equivalency you should be able to get it right.

msiemsen:
Incandescent lights generate heat at 100% efficiency, if you measure efficiency by the conversion of electric energy to heat. This is a really bad way to use electricity, because that electricity was generated from some other energy source and then sent through lossy wires at probably something like 20% efficiency. A gas furnace can be 95% efficient. A heat pump is much more than 100% efficient (if you measure efficiency by the energy consumed divided by the energy added to the house). If you are in fact heating your house with resistive electric heat, like a giant light bulb, you should give some serious thought to switching.

I have no connection to GE, but I’ve found their catalogs informative. Below are links to their compact fluorescent catalog and their linear fluorescent catalog:

http://www.gelighting.com/na/business_lighting/education_resources/literature_library/catalogs/downloads/Lighting_and_Ballasts_Section_5_Compact_Fluorescent_Lamps.pdf

http://www.gelighting.com/na/business_lighting/education_resources/literature_library/catalogs/downloads/Lighting_and_Ballasts_Section_5_Compact_Fluorescent_Lamps.pdf

If you look at the lumen numbers, you’ll note that they give an “initial” lumen value and a “mean” lumen value. The “mean” value is labeled as the light output at 40% of bulb life. For a randomly chosen CFL I observed an initial lumens output of 1350 and a mean output of 1135. What does that mean? It means that when the bulb is 40% through it’s life it’s only producing 84% of the light it produced initially. And this will presumably decrease *roughly* the same amount again going down to the end of life, meaning something like 68% of full output at that point. This is quite a significant change, and one that could be troubling even to young eyes.

If you take a look at a 4 ft long T8 bulb, the standard nominal 32 watt fluorescent you’ll notice that the lumen output only falls to 94% for the mean output. So there’s another reason beyond simple efficiency to really use the linear fluorescent fixtures if you can rather than using CFLs.

I’m hoping for good, dimmable, LED lighting. But it doesn’t seem to be here yet. I’m curious, though, about color rendering. How can LEDs produce a good CRI without using the same phosphors as the fluorescent lamps? I thought that white LEDs worked essentially the same way, with a high frequency output being modified by phosphors. In fact, I heard that at least in some cases the LED might last 100,000 hours but the phosphor coating would only last 10,000 so the light wouldn’t maintain it’s color over time.

Add more lights to your workshop.

So year by year things will indeed be dimmer in your workshop even if you change the bulbs every couple of years.

I am in love with the new fluorescent, electronic ballast 4 foot long tubes. I have changed my whole workshop out to 5000K fluorescent light bulbs and tubes.

It’s a downside to CFL bulbs that you can’t replace the ballast. I use them throughout the house and basement but I replace them every two years. For spot lighting I stick to old fashioned carbon arc bulbs. Just kidding. GE daylight.