This post will evolve over several weeks. Please watch it grow. And, know conclusions have already been expressed here over the four or five years largely mis-spent since excellent LED disk downlights became available for home installation. LED lighting will improve global quality of life and productivity, while hugely contributing to saving of grid electrical power used for residential lighting. Only about 10% of the potential has been achieved so far in the USA. Ref: Adoption Report, USDOE, 2017 .
Here are discussions in this blog:
Focus please on the word Brightness of the post title. Go with me to the linked Wikipedia article, and find disastrous confusion sowed by the US Federal Trade Commission in the matter of Lamps, the topic here:
The United States Federal Trade Commission (FTC) has assigned an unconventional meaning to brightness when applied to lamps. When appearing on light bulb packages, brightness means luminous flux, while in other contexts it means luminance. Luminous flux is the total amount of light coming from a source, such as a lighting device. Luminance, the original meaning of brightness, is the amount of light per solid angle coming from an area, such as the sky. The table below shows the standard ways of indicating the amount of light.
Today, dictionary.com has
1. any of various devices furnishing artificial light, as by electricity or gas.
There can not be a justification by FTC, to imagine and apply only light bulb point sources as lamps. And, of course an LED light bulb is not a point source. An LED bulb hemispherical lens glows to the side with task lighting efficiency of less than 30% of total lumens. About 70% of typical A-type LED bulb illumination is sent from a circuit board parallel with the base; a nasty and dishonest trick when upright in a table lamp or horizontal in a ceiling fixture. A large fraction of emitted light is lost in the thick diffuser. A wasteful device must not be promoted as other than decoration, without offer of purchase incentives.
A cheap and short-lived A-type LED bulb has sideways illumination like that of the old 100 watt incandescent, and is 40% brighter end-on. If used in a table lamp for reading, 40% of power is wasted.
Here is proof from test stand comparisons. At left "100 watt" incandescent bulb. At right EcoSmart ICES-003/B LED, 800 lumens, 10 watts, 3000°K. At full power. The EcoSmart is turned 90° to illuminate the screen with cast from glow of the lens hemisphere as it might in a table lamp or horizontal ceiling fixture. The EcoSmart side illumination is about 500 lumens, equal to that of a "100 watt bulb."
At left "100 watt" incandescent bulb. At right EcoSmart ICES-003/B LED, 10 watts, 3000°K. At full power. The EcoSmart is now straight-ahead to the screen and quite superior to a 100 watt bulb, the effect of 800 lumens, not the useful 500 lumens of a 100 watt bulb. Judge that the EcoSmart if placed upright in a table lamp or horizontal in a ceiling fixture is with usefulness ratio 500/800, about 40% energy waste.
We must go back to the correct usage of brightness as luminance, to inform our decisions, as we develop and select luminaires that ever-better, make light a cost-free resource to enrich human activity. Luminance is first a measure of the illumination to our eyes, of tasks at hand. Nearly as important, it is the test of glare as we gaze upon the luminaire. Glare as a nuisance or hazard, is not regulated and not listed in competition for purchases. Lights continually cheapened and glaring, discredit the switch to LEDs for energy conservation. Where best LED lights will serve essentially forever, we can afford that they be built without weak electronics, easy to look at.
Following the FTC mis-direction, we are taught that lumens count, luminous flux in all directions, is the modern way to compare lighting choices.
Here is an example:
C/Net, Smart Home
Watts vs. lumens: How to choose the right LED light bulb
Article by Alina Bradford, May 9, 2017
These comparisons are meaningful only for light in antique candle form, as point source illuminating a beam angle of about 320°. Achievable brightness of such old-fashioned bulbs actually can't exceed that of the well-known "100 watt bulb." Wiring that fed a 150 watt bulb was usually destroyed by heat. The table perhaps consciously under-values LED lighting, where LED tricked to look like point-source incandescent and CFL bulbs, has not been offered at more than about 15 watts. All LED luminaires of higher wattage are of other form, as directional flat plates, the natural display from diodes on circuit boards; and do not belong in this table. Disregard as ridiculous, "corn" LED bulbs at the high end of table wattage.
About half of point-source light is fully wasted where the purpose is task illumination as in reading. The comparison prevails where something is sought to fill A-Series light bulbs with their global confusion of sockets, in USA and other countries with 110 volt mains, E26 threaded.
We have long had lighting that is not dissipated as point-source, to confuse a relationship of watts to potential task illumination.
Again, before LED lighting became practical, interim CFL point-source and flood or spot bulbs, muddied watts as a measure of brightness.
The wrong teaching is in failing to distinguish lumens count from a directional light such as an incandescent flood, from wastefully-thrown light of point source bulbs.
Hereafter let Luminance be a controlling factor in luminaire planning and design.
Look at luminance numbers for some existing edge light LED examples:
Cooper SLD6: 0.064 lumens/ mm2
Conturrent 4": 0.074
Lithonia WF3: 0.228
Lithonia WF4: 0.124
EiKO 5": 0.059
Try imposing a uniform lens luminance limit of 0.05 lumens/ mm2
Tabulate lumens and lens diameter at this limit: