Re: e-watt LED light bulbs - what has been your experience
 

FWIW:


60 watt incandescent 840 lumens

40 watt incandescent 490 lumens


LED T-67004M (Cool White 5000K) 560 lumens

LED T-67004S (Warm White 2700K) 450 lumens

Re: e-watt LED light bulbs - what has been your experience
 

In the picture I posted--
--the bulbs are horizontal
--the frosted glass shade is below them
--there is no shade above them
--the ceiling is moderately dark (main reason why this room is hard to light)

So maybe my "test" should include a situation such as in a table lamp, where the bulb is upright and lights up the ceiling and walls. One thing I haven't done is to try it at night, when there is no outside light. To be truly "scientific," though, I would have to remove all the furniture and somehow take a picture of the floor, but how could I do that without blocking the light with my camera? Oh, well. I guess the main thing is whether we decide we like it in our house.

Re: e-watt LED light bulbs - what has been your experience
 

I know, but all that really tells me is that a lumen rating is a poor indicator of how a bulb 'looks' in a room...

Re: e-watt LED light bulbs - what has been your experience
 

This is an extremely true statement. While lumens are an important metric when evaluating light, there are often many other factors to consider.

When dealing with LED bulbs in particular, higher CCTs (color temperatures) result in a higher light output (for the same drive current). Essentially, higher CCT LEDs are more efficient than lower CCT LEDs because the phosphor conversion of blue light to white light is less dramatic.

Many companies will try and squeak a few more LPW (lumens per watt; essentially how efficient the bulb is) out of their fixtures and bulbs by bumping the CCT up a little bit and essentially gaining free light.

CRI (color rendering index) is another very important measure, albeit a controversial one at times. CRI basically tells you how well the light coming out of the bulb/fixture renders colors. The higher the CRI (max=100) the closer it is to natural sunlight in terms of color rendering. You can read more about CRI here: http://en.wikipedia.org/wiki/Color_rendering_index

One last measure which has a lot of play in LED lighting is lux. Lux is a measure of ILLUMINANCE, not LUMINANCE. Lux takes into account how much light is being emitted over a certain area. In situations which are a direct replacement for incandescent or flourescent bulbs (such as the FIRST bulb) it is not as useful, but for other LED retrofitting applications it is extremely useful. One example of where lux is extremely important is in streetlighting. Streetlighting has very specific requirements for lamps to meet so roads/sidewalks/parking lots are lit correctly. Just putting a big light source in a fixture will not necessarily give you the correct light output. To ensure the beam is being spread and shaped correctly, measuring lux at specific areas of illuminance will tell a better story of how well the light fixture is working.

These are some more metrics that can be useful when evaluating light, and LED lights in particular. As with most things, there are direct tradeoffs between things like cost and efficiency, CRI and output, etc. It is our job as engineers to find a balance that consumers will enjoy!

-Brando

Re: e-watt LED light bulbs - what has been your experience
 

... and they do the opposite (lower the color temperature) with incandescents to create "long life" bulbs.

60 watt standard 840 lumens

60 watt "long life" 770 lumens


Don't forget that the user can easily lower the color temperature and/or change the lighting pattern by selecting a different lamp. A different lamp can completely change the look and feel of the same bulb in a given room. A glass bowl or reflector which directs the light upwards to reflect off the ceiling produces a completely different lighting pattern than a lampshade that is narrow at the top and wide at the bottom to direct the light downward. And a white lampshade produces a different "feel" in a room than a dark color.

Re: e-watt LED light bulbs - what has been your experience
 

I have way less of an understanding of how incandescents work so I cannot speak to them as well as LED, but how do you tune the CCT of an incandescent bulb? Just curious, it seems like a pretty interesting thing to do.

Lighting is all about "feel" as you have said. Unfortunately its extremely difficult to put measurable metrics on feel, which is why lighting is sometimes a very tough market to penetrate. As you said, options must be available for users to make their own choices of what feels right to them.

I do have to say however, since I began working on LED lighting around 3 and a half years ago, I now prefer cooler feel temperatures (higher CCT). Nothing in the 4500K+ range, but a 2700K temp actually feels wrong to me now.

-Brando

Re: e-watt LED light bulbs - what has been your experience
 

The user can change the color temperature of an incandescent bulb by dimming it.

The manufacturer makes long-life incandescents by changing the filament slightly so it doesn't burn as hot. That gives a yellower light, and the filament lasts longer. And the bulb is less efficient (fewer lumens per watt).

Re: e-watt LED light bulbs - what has been your experience
 

Reported

Re: e-watt LED light bulbs - what has been your experience
 

What kind of watt meter would you use?
What brand? Where would you purchase it?

Re: e-watt LED light bulbs - what has been your experience
 

Our display has places for 4 bulbs so we can compare the color and directionality of the bulbs. Maybe we should get incandescent bulbs with the warm and cool designations to use in the display.

Karen - I can't tell the difference in your photo. You may have found the perfect application for a 40 watt LED that looks like 60 Watt in one direction!


When I next see our display and /or the builder of it, I'll get the details on the watt meter. All I remember it that it plugged into the outlet and had a digital read-out!

Re: e-watt LED light bulbs - what has been your experience
 

Budget-conscious consumer electronics vendor Vizio is getting in on the act... reported here: http://www.engadget.com/2011/06/22/v...es-a-light-bu/

"...A Vizio price..."

Re: e-watt LED light bulbs - what has been your experience
 

Well, I got my first bulb yesterday, and boy are they directional. I have a standard lamp in the living room, and the LED bulb does not cast enough light downwards to read by - while a 60W incandescent is almost too bright.

On the other hand, in a downward-facing ceiling fixture, they are excellent.

Thank you PaW for the Vizio link; using a cheap bathroom light bar as my demonstration board will save me a bit of grief.

As for wattmeters: I am planning to get four $3 Harbor Freight digital multimeters, connect them to show Amperes for each of the four bulbs I want to display (LED, CFL, 40 or 60w Incandescent, 45 or 65W R30). People will see bigger numbers for the Incandescents, that'll be all they need. Done, & done.

Re: e-watt LED light bulbs - what has been your experience
 

I wish I could try one in our table lamp. However, we generally use a 150-watt 3-way bulb, so trying any 40-60-watt bulb replacement would not be a fair test!

Re: e-watt LED light bulbs - what has been your experience
 

For a user friendly meter you could also use something like this for $21.

Re: e-watt LED light bulbs - what has been your experience
 

I would watch out for those meters. I looked at some of the reviews and a lot of them said the meters were prone to breaking. And trying to show a potential costumer watts with a broken meter may not help you sell this product.