Okay, you make a good point. I didn't expect that would inspire anyone would stare at a bright LED. I have for reasons of liability recommended to a client to hang a warning about staring into the grow lights with a PDF of the warning sign attached. And I said light bulb not LED. Although I have not found any lighting LED that exceeds a "moderate risk" group ranking.
The specific brightness was a legitimate find and I appreciate that. I tried and could not verify it to be true but I will go as far as to say it is not true. But I have to say it's not very likely to be true. Something I would file under "someone said in the Internet".
Still it does not help SneekyNinja though. Specific Brightness according to that scienceworld.wolfram site is an alternate term for Intensity. Only further confuses what SneekyNinja said.
The problem with the "definition from scienceworld.wolfram is it is nonsensical.
The brightness
(more properly known as the specific brightness) is the intensity of a radiating source (i.e., the energy flux per solid angle per unit of frequency), also called the radiance or surface brightness.
As far as surface brightness, I believe the author meant black body temperature, or color temperature (e.g. 4000K). The term "per unit frequency" makes little sense in this context. Energy Flux is not a common phrase. Intensity is flux per solid angle. Flux is energy per unit time. That screws with the time domain. Then adding unit frequency blows the time domain out of the water. Unit frequency is weird term. A unit of frequency would be Hz.
For sure, intensity is NOT the same a radiance.
