Sunday, August 25, 2013

Cree "60 Watt" LED Bulb

Here is an exercise in use of Brightness Numbers to compare point source bulbs with  LED downlights.

This post was originally offered on 8/25/2013, for comment about a bulb newly   fussed-about      "60 W" bulb from CREE.  I bought one of these at Home Depot, for $12.97, in May, 2013. My findings damn the product and impugn the judgement of those praising it. I have felt OK about keeping mum, for a few months.

A 60 watt equivalent bulb already existed, and was the subject of the initial L-Prize. The prize-winning Philips bulb presently costs more, perhaps $38 vs. $13, with poorer efficiency, drawing 12.5 watts vs, the new CREE at 9.5 watts, 65 lumens per watt, and with same claim of durability, life more than 25,000 hours.  The CREE at reported 800 lumens, is 84 lumens per watt, but I doubt that high number, where 65 lumens per watt seems ordinary current manufacturing technology.

A 22 watt similar Philips is reported 1780 lumens, 81 lumens per watt, and costs $69 each at Amazon right now.

The new CREE bulb is progress, for residential decorative illumination. It is not progress in residential task lighting, where Glimpse or Sylvania projecting planar LEDs serve best. I offer side-by side comparison of illumination, including statement of Brightness Numbers, where a CFL or LED bulb is accepted as an illumination  match with a stated-equivalent incandescent bulb. May, 2013 observations here don't include yet-to-be offered Sylvania 70732, 900 Lumens, too bright for sight comparison.


I don't really accept that the Cree 60W LED bulb has brightness 2.4. The 4" Glimpse, dimmed to B2.4, would give 270 lumens. If a 100 watt incandescent gives 1490 lumens, a 60 watt equivalent point source is about 900 lumens. I think the Cree product is advantaged for some reason, by at least 10%. B2.4 times 800/900, is B2.1, and that is still not a credible number. Way too high.

Here try comparisons at same color temperature, full power. Imagine the 4" Glimpse dimmed to B2.2 at 60 watt equivalence. The Cree 60W LED would surely still be less bright. B2, or whatever, the Cree 60W LED is not useful illumination.

Within 24 hours of purchase, this CREE 60 watt LED was broken. My test stand thudded to the floor in a 6" rotation, and the glass globe separated from its base. What a pitiful light. Perhaps carelessness came from poor attitude. But, now I get to look inside.

The broken CREE 60 watt LED bulb is a pretty toy for a moment. Then comes sadness. An LED light should live for very many years.

Posted photos are from this captioned web album.

At November 2013, this post is edited to employ phrase "projecting planar LED." With the notion no light should be recessed, seek an antonym, and coin that phrase. Do you like it? The aim is to define lighting that may be retrofit with future organic LED lighting, OLED. Surely OLED will never be tricked to act as a point source. Where OLEDs are best buy, we will increasingly throw out our dear bulb fixtures.

The original post used phrase "plate LED," intended as a brief statement that the luminaire is fully revealed upon the ceiling surface and may be wired directly into a junction box.  That phrase  is confused with license plate lighting, and is not accepted elsewhere.

At end-October 2013 I edited in phrase "surface mount LED," in some of my posts. Then I realized that even an incandescent bulb on a porcelain holder, is surface-mounted.

Projecting Planar LED lighting is not recessed for foolish styling reasons, to look like a can-mount downlight. Can-mount downlights were a consumer adaptation of theater downlighting, where upon a black ceiling, there is nothing bright to divert attention from a stage. In any circumstance other than a stage center, there has never been a bit of virtue in recess setting of a light. It has been quite disastrous in our waste of the Earth's ready fuels, that many have loaded their can lights with bulbs that are simple point sources, with no reflector bouncing to usefulness, the light that otherwise does not beam downward; all such light and heat energy, totally wasted.


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