Usually ultrabright 5mm LEDs are about 18000 mcd bright. I found some on ebay which claim to be 40000 and even 140000 and 290000 mcd bright. That is about 16 time as bright as a normal ultrabright LED. Is that a scam or is it true. If yes, why would anyone still sell such dim ones as 18000mcd? Thanks examples:
Usually ultrabright 5mm LEDs are about 18000 mcd bright. I found some on ebay which claim to be 40000 and even 140000 and 290000 mcd bright. That is about 16 time as bright as a normal ultrabright LED. Is that a scam or is it true. If yes, why would anyone still sell such dim ones as 18000mcd? Should I get 290000mcd LED for building a photographic light panel? Will they suck much more juice? Thanks
examples:
As long as they dont tell you for how long they survive, any LED can be sold for any brightness(almost).
I dunno if you noticed that the LEDs you referenced are 10mm (about 3/8") diameter. These are typically called Jumbo LEDs, which are fabricated with numerous individual chips in one acrylic capsule.
If you look closely at a common 5mm clear acrylic LED with a magnifier, you'll notice that there is a small chip located on top of one of the terminals, with 2 very fine gold wires bonded to it (and the terminals).
In the Jumbo LEDs, there are more than one chip, the second eBay listing below states that there are 5 chips in each of those Jumbo LEDs.
I haven't tried any of the Jumbo LEDs to experiment with, but I would expect the amount of light to be equivalent to 5 super bright common 5mm LEDs. If you have any inexpensive flashlights with about 5 super bright LEDs, that's probably approximately what can be expected.. brighter than 1, but not necessarily a high intensity light.
Numerous common 5mm LEDs provide more light for illuminating a small, close area, but the higher power LEDs (1W, 3W, 5W) are capable of producing higher illumination at a distance. The high powered LEDs require heat sinks, but the 10mm eBay LEDs don't. That might give you an indication of the differences in intensity.
The high power LEDs are impressive, and perform even better with a suitable reflector. The wide reflectors for incandescent flashlight bulbs/lamps aren't as effective with a high power LED as reflectors with a narrower angle, IMO.
-- Cheers, WB .............
Here is a good article on LED's and the problem with their brightness in this month's IEEE Spectrum... It discusses why LED brightness is limited, if you are interested.
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