With all the discussion about the new Cree LED lightbulbs, I decided to buy a Cree 9.5W (60W) warm bulb and compare it to a 13W (60W) compact fluorescent light (CFL) and a regular 60W bulb (incandescent).
The Cree 9.5W (60W) warm bulb is rated at 800 lumens and 2700K on the package, the Sylvania 13W (60W) CFL is also rated at 800 lumens and 2700K, and the Philips 60W incandescent is rated at 830 lumens. There’s no temperature given for the Philips although it is designated “soft white” (as is the Sylvania CFL).
I put each bulb in a lamp in a dark room with the sensor of my luxmeter at the base of the lamp. I set the meter to record at 2 second intervals, turned the light on and recorded an hour of data for each bulb. I then put it all in one spreadsheet and made this graph (not by hand my meter writes to an SD card).
I measured lux over time at the base of the lamp, not lumens, and this is a comparison of my three bulbs only. It wouldn’t be correct to say for example that all 60W replacement CFLs are brighter, only that this one was. Or even that all CFLs ramp up like this because some of the newer ones are closer to “instant on.”
What I find most interesting is not their relative lux readings but how their outputs varied over time and also how consistent (or not) each bulb was. The Cree in particular stabilized to the point of flatlining just after the 30 minute point here and during another test I ran. I collected 3 hours of data on the Cree during that other test and it remained within a 2 lux range for the final 2 1/2 hours.
I was just mumbling about those new led lightbulbs, and you shared some light on the subject, LOL!
Interesting to see also how over-rated all those bulbs are: they average 600 lumens when they are sold as 800... not very honest... maybe the producers learned very well the syndrome of chinese-lumens!!
Lux value apart, how would you judge and compare by eye the quality of lighting in the room with the three bulbs? differences? Does the led bulb achieve an even light spread?
Imagine for example an incan light hanging from ceiling having to enlight the whole room: a led bulb would be ok or is it more suited to spot lights?
According to the Cree data sheet it is: “Made with a glass bulb like an incandescent, the light from Cree® LED bulbs comes on instantly and is omnidirectional.” http://www.cree.com/lighting/landing-page/cree-bulb
With that said, it’s probably not precisely omnidirectional but for my purposes it’s close enough. For the above reason and more importantly because 85% of the light hitting the sensor is reflected downward from the lamp shade. That number comes from readings taken with the shade on and off.
Take the relative lux readings at face value. Obviously placing a sensor under a lamp isn’t an integrating sphere but it was in the same place for all three bulbs and, as I said in the OP, that’s not the most interesting aspect of the readings anyway IMO.
i’ve seen pictures of it lit, and it closely mirrors the led placement inside, which i think is disappointing, i would prefer it to be omnidirectional like a cfl or incandescent.
Its no surprise the brightness falls after its been turned on, its an open secret about LEDs, but if i were considering it i would buy one and make sure it suits my purposes before purchasing more
since its not omnidirectional, we can’t assume the total lumens are lower then advertised based on your test, but we can say its lower lumens then the competitors in the test zone
You’re welcome. The main subjective judgment I can make is it does seem a little less bright than the CFL and I say that because after the tests I put it in a lamp in my living room where I’ve had a CFL for years and every time I see it I get that impression. But overall I’d say the quality of the lighting is excellent. I haven’t hung a Cree LED bulb from the ceiling but I think it would work well because Cree claims they’re omnidirectional and mine looks like it is.
And your basis for disagreeing with Cree that it’s omnidirectional is that you’ve seen a picture of one? I actually have one and it looks at least as omnidirectional as a CFL or an incandescent to me. Maybe you should buy one and see for yourself. Also I made no claim about lumens.
I bought a couple to play with… not impressed… the heatsink is WAY too small and that silicone condom over the glass bulb is … icky …
Note that the absolute values of my lumen numbers may not be correct since I have to stick the whole bulb into the sphere and all my calibration sources emit only from the inside wall of the sphere.
my meter writes to an SD card).
I actually have one and it looks at least as omnidirectional as a CFL or an incandescent to me. Maybe you should buy one and see for yourself. Also I made no claim about lumens.