BabyPeanut wrote:Well I got my bulb. It has a beam spreader that is rated at 80 degrees... At 2 - 2.5 watts it will take all day to use a fraction of the energy a compact fluorescent would use overnight on a timer plus there's no timer using electricity.
Your case sounds like area lighting (vs task lighting), and I might have recommended a 3W compact fluorescent bulb. They are available, and probably put out considerably more light over the desired area than your LED with a spreader.
IMHO, putting a spreader on a LED is not the best thing to do. You lose it's biggest advantage -- tight focus, without gaining the advantage of fluorescent lighting -- high efficiency over a wide area. And mimicking fluorescent's wide angle with a spreader comes at considerable financial penalty, as well.
The 3W CFBs I use came from China via Home Depot (unfortunately) and have a miniature, "christmas bulb" base, which would probably have to be adapted to your fixture, which is another consideration.
If someone bugs me, I'll go in the lab and make some actual measurements to report. (I've done this before to my satisfaction, but can't find the back of the envelope where I put the data... :-)
Efficiency ratings in lumens is deceptive. For task lighting, illumination should be compared in lux, which is illumination over a given area. "Luminance" is measured in lumens, and measures the light given off by a light source. "Illuminance" is measured in lux, and measures the light falling on an area.
For example, if one device produces 100 lumens, uniform over an entire sphere, and another device produces 10 lumens, but directs it all to 1/10th the area of a sphere, they produce the same illumination over that 1/10th of a sphere, but 90% of the output of the 100 lumen source is being wasted. This is why fluorescent bulbs seemingly have greater luminous efficiency than LEDs, but may actually have far less illuminous efficiency over the desired area to be illuminated.
At first glance, <i>samllpoxgirl's</i> figures appear to give fluorescent light up to a 6x improvement in efficiency, but in reality, concentrating a fluorescent's total lumination into 1/6th of a sphere illumination is not trivial, and as the desired beamwidth narrows beyond that, LEDs hold increasing advantage.
<b>Summary:</b><i> area lighting, think fluorescent; task lighting, think LED, or halogen with integrated reflectors.</i> A single 20W reflector-halogen illuminates my desk with more light than a four-tube, 200W fluorescent fixture mounted on the ceiling in the center of the room.
Hope this clarifies things a bit!