The Brightest and Most Efficient LEDs and where to get them!

Latest update 9/23/2001.

Back up to my LED main page, ledx.html.

News and links!
General Notes and Disclaimers
Red LEDs - 11-22+ lumens/watt by Agilent, and a mystery 23-24 lumen/watt orangish red, soon 42 by Lumileds.
Red-Orange LEDs - 21-22 maybe now 28.5 lumens/watt by Agilent, 15 by Toshiba, soon 53 by Lumileds.
Truly Orange LEDs - 18-22 lumens/watt by Toshiba, 18-21 lumens/watt by Agilent.
Yellow and "amber" LEDs - 14-16 lumens/watt by Toshiba and Marktech and maybe AND, soon 35-35 by Lumileds with 20-21-plus known achieved, 13 to maybe now 14.5 by Agilent.
Yellow-Green LEDs - 3-4 lumens/watt by Toshiba and AND, but there is a way to get 20-40.
Green LEDs - 25-32+ sometimes 42 lumens/watt by Nichia, 16-plus by Toyoda Gosei, maybe Agilent.
Nichia green LEDs get 30-55 lumens/watt at 5 milliamps
Blue-Green LEDs - 25-28 lumens/watt by Nichia, soon 25 by Lumileds.
Blue LEDs - 7.5-probably 8, rarely 10 lumens/watt by Nichia, 5.5-plus by Toyoda Gosei, maybe Agilent, soon 9-plus by Lumileds, soon 12 by Cree.
White LEDs - 15-16 sometimes 18 lumens/watt by Nichia, and 10-plus by Toyoda Gosei and Agilent, soon 15 by Lumileds, maybe soon 20-25 for ones with new Cree chips.
General info on Nichia Gallium Nitride and InGaN LEDs.
Increased Efficiency of InGaN LEDs at lower currents
Important Notes on Gallium Nitride and InGaN LEDs!
Photon "Micro Lights" Keyring LED flashlights.
LEDs with high candela "beam candlepower" figures
LEDs with high total lumen output
Notes on Where To Get Bright LEDs
Converting / comparing lumens, candelas, millicandelas

News and links!

UPDATE 8/29/2000 - Agilent and Philips Lighting have a joint venture Lumileds. Their web site has some higher output LEDs that I could not find in any site.

UPDATE 2/13/2001 - Lumileds announces on 2/9/2000 a 25 percent efficient 425 nm blue-violet LED. Their previous record was 22 percent.
This is "wall plug efficiency" or conversion efficiency, the percentage of energy going into the LED that gets radiated as opposed to quantum efficiency, which is the ratio of outgoing photons to electrons passing through. If the photon energy in electron volts equals the LED voltage drop in volts, then the wallplug efficiency and the quantum efficiency are equal. In GaN and related LEDs, the wallplug efficiency is noticeably lower than the quantum efficiency.
The 25 percent efficient 425 nm device seems to be a high power one, with an optical output of 200 mW for 800 mW of electrical power. According to the above Lumileds article, this device was demonstrated to handle even higher power, producing 525 mW of optical output at a current of 1 amp.

UPDATE 4/18/2001 - Lumileds has a prototype high power white LED producing 17 lumens of light at 350 mA with a voltage drop of 3.2 volts. The overall luminous efficacy is 15.2 lumens/watt. More in this 2/26/2001 press release.

UPDATE 8/28/2001 - PDF Datasheet on Cree "Mega Bright" blue dice/chips. Typical optical output 10-11 mW at 20 mA.

UPDATE 2/11/2001 - Cree has a 2/8/2001 press release claiming 32 percent quantum efficiency for a 390 nm deep violet-borderline-UV LED. The claim includes 21 mW out at 20 mA.

UPDATE 7/30/2000 - Cree's previous record of 22 percent percent conversion (wallplug) efficiency and 28 percent quantum efficiency - info at the web site of Compound Semiconductor magazine. 17 mW of 400 nm deep violet, presumably at 20 mA, details in a July 28 2000 press release at Compound Semiconductor magazine.

The above near-UV to violet-blue LEDs have a main future application of being combined with phosphors for producing white light.

UPDATE 12/1/99 Agilent has some improved models working in the lab already. Odd shaped LED dice such as a truncated inverted pyramid let more light out than rectangular ones, often nearly doubling light output and efficiency. Since less of the input power becomes heat, input power can be increased for even more light output.

Look in for more details - including claims of overall luminous efficacy as high as 102 lumens/watt for orange and 68 lumens/watt for orange-amber in laboratory test versions of these LEDs.

Compound Semiconductor magazine (the May/June 2000 issue) has mentioned surface texturing to increase efficiency. This seems to be another approach to reduce total internal reflection trapping of photons. Total internal reflection is a serious issue in many LEDs due to the extremely high refractive index of some LED materials.

Hewlett Packard's LED manufacturing is now part of a spun off company known as Agilent. Links updated/checked 4/29/2001.

Agilent LED top page,

Agilent white LEDs
Agilent pure green LEDs, traffic signal green LEDs, blue LEDs

Agilent Orange-Red, Reddish Orange, Orange and Amber "Sunpower" LED Lamps of beam angles 6, 15, 23, and 30 degrees.
Agilent HeNe Laser Red, Reddish Orange ("taillight red"), and Amber "Sunpower" LED Lamps with "AlInGaP-II" of beam angles 15, 23, and 30 degrees.

Now for a link to a Cree datasheet with their latest and greatest production LED chips (no whole lamps). Overall luminous efficacy is better than before but still below that of Nichia. Includes 460 nm deep blue with overall luminous efficacy of 4.7 lumens/watt but with "blue impact" (usefulness as a blue primary for RGB devices) like that of 470 nm blues that get 8 lumens/watt. Here is the link to the PDF datasheet:

Click Here for

You definitely want to look at Craig Johnson's LED Page. Mostly subjective but useful results of many LEDs including some of the champs below are included. Beam pattern illumination of a test target is shown for many of them.

General Notes and Disclaimers:

I don't know everything, and I only mention LED brands and models I know of.

Luminous efficacies were largely determined by one or more of several methods, mostly almost laughably crude. I give NO warranty as to accuracy. I have at times slightly changed my estimates for some models. Your mileage may vary.
Unless otherwise noted, luminous efficacy is stated for a 25 degree Celsius (77 degree F.) ambient with a current of 20 milliamps in an environment that does not build up heat around the LED. Red, orange, yellow, and yellow-green models mentioned here generally have maximum efficiency at currents around 20-25 milliamps. Efficiency of these is less at low currents of a few milliamps or less. The decrease is not as bad with GaAlAsP and "T.S." AlGaAs and Agilent's most efficient InGaAsP red ones as it is with most other InGaAsP (orangish red through yellow-green).
Indium gallium nitride types (most ultrabright blue, blue-green, non-yellowish green, and white types) usually have efficiency that increases with decreasing current, although the increase will reverse as current decreases below something like 2 mA.
Please beware that performance of many LED models at currents below a few tenths of a milliamp may be unreliable.
There may be significant tolerance in light output. Your mileage may vary.

Some of these LEDs radiate light of slightly different colors in different directions. This is most apparant with white models and narrow-beam yellow models, as well as the most efficient yellow-green models.

PLEASE NOTE that the lumen per watt figures in this document are lumens of light produced per watt of electricity delivered to the LED. Many LED manufacturers state much higher figures indicating the lumens per watt of radiated light. The latter, high figure is typically in the ballpark of 65-100 for red, 130-180 for orange-red, 220-265 for red-orange, 440-500 for yellow, 400-plus to 660 for green, and around 50-90 for blue. If the conversion efficiency and the "high" lumen/watt figures are both known, multiply them to get the lumens out per watt in.

Beam brightness and width figures below are mostly ones claimed by manufacturers/distributors and I have NOT confirmed most of these.

UPDATE SPRING 1999 - The brightest Agilent / H.P. HLMP-D??? models have been superceded by models with HLMP-E??? part numbers. These seem to be pretty much the same thing, but with subtypes graded on measured beam intensity and in some cases on color. Check into the Agilent "Sunpower" links above.

Agilent distributors such as Newark Electronics, Allied Electronics and Hamilton Hallmark will not have all of these most amazing Agilent LEDs in stock. Special orders could require a substantial minimum order, like 500 pieces, and also lead times of a couple months!

Red LEDs - 11-22 lumens/watt by Agilent and a 23-24 lumen/watt mystery LED.

UPDATE 7/5/2001 - I just got some datasheets from Lumileds on their Luxeon series that is about to go into production. The "high dome" red Luxeons will supposedly produce 30.6 lumens minimum, 44 lumens typical at 350 mA with a 2.95 volt typical voltage drop. This is 29.6 lumens/watt minimum (assuming the typical voltage drop), 42.6 lumens/watt typical. I expect overall luminous efficacy to be even a little higher at somewhat lower currents around 200 mA. I am guessing that this model uses those truncated inverted pyramid dice mentioned above.

The "Low Dome" is not as efficient and produces less light. My guess is that the high dome but not the low dome use truncated inverted pyramid dice.

UPDATE 12/28/2000 - an orangish red LED that Craig Johnson sent me just checked out at 23-24 lumens per watt but he has been unable to identify it. This part is a usual size 5 mm clear LED lamp with a beam about 23 degrees wide. The dominant wavelength was about 626-628 nm, orangish red. Optical output was 7.3 mW at 20 mA with a forward voltage drop of 2.4 volts. I believe the luminous efficacy of the emitted light had to be 150-160 lumens per watt, more likely closer to 160.
With a majority of that approx. 1.1 lumens being in a 23 degree beam, the brightness would be somewhere around 5 candela. And the 15.2 percent conversion efficiency is impressive!

Back to known bright and efficient red LED lamps:

The HLMP-DD16 is a very slightly orangish red LED lamp with an overall luminous efficacy ranging from 18 to 22 lumens per watt according to my tests on samples in July 1998. The conversion efficiency is the best I have seen of any bright LEDs - varying from 13 to 16 percent.
UPDATE 1/1/2000 - I got some more from Newark Electronics and tested some of them - efficiency was mostly around 15 lumens/watt, as high as 17 and as low as 11. However, another H.P. model that I got through Newark (HLMP-DJ24 true orange) exceeded my expectations.

This is a 5 mm. (T1-3/4) lamp. Rated brightness is 3.6 candela and the nominal beam diameter is 15 degrees. Peak wavelength is 639 nm and the dominant wavelength (color matching wavelength) is 630 nm.
UPDATE 3/26/2000 - Agilent HLMP-E*** types mostly come in 2-3 brightness-sorted subtypes. Check out the Agilent links above.

Other bright red models:

UPDATE 5/27/2001 - Toshiba TLRME20T, Hosfelt 25-405, 12.5-14 lumens/watt, claimed brightness 8 candela. Not as orange as other Toshibas below.

Toshiba TLSE20T, Hosfelt 25-406, - not tested, interpolated 14-15 lumens/watt. Very orangish red, claimed brightness 9 candela.

UPDATE 1/4/2001 - a few various Toshiba orangish red LED lamps with dominannt wavelength around 626 nm seem to get around 14 to maybe sometimes 15 lumens/watt. This is for some samples sent to me by Craig Johnson. Models of samples that did about this good include TLRH180P and TLRMH151P.

UPDATE 3/16/2000 TESTED Toshiba's TLSH180P (Hosfelt 25-359, US$ .79 as of their 2000-A catalog) 8 candela 6-8 degree beam VERY orangish red more like red-orange - 15-16 lumens/watt! Similar but untested is AND's AND180HSP (Newark 52F6144).

Agilent HLMP-8103, 9 lumens/watt, 3 candela, 7-8 degree beam, peak wavelength 650-654 nm, dominant wavelength 640-644 nm.
Agilent HLMP-C116, 9 lumens/watt, 2 candela, 14 degree beam.
Agilent HLMP-C124, 9 lumens/watt, 24 degree beam.
Radio Shack 276-203, 8-maybe 8.5 lumens/watt, slightly oval basically 5 mm. diameter, .4 candela, pointed-oval beam 70 by 30 degrees.
Radio Shack 276-309, 8.5-maybe 9 lumens/watt, 40 degree beam, 800 mcd.
Radio Shack 276-307, 8-maybe 8.5 lumens/watt, 7 degree beam, 3,000 mcd, $1.99.
Radio Shack's 276-086A 8 lumens/watt, 10 mm. jumbo lamp size, 5 candela, 4 degree beam, peak wavelength 665 nm, dominant wavelength 648-650 nm deep red, conversion efficiency 12-13%
Radio Shack 276-086 (without the A) 7-8 lumens/watt.
Radio Shack 276-087 (without the A) varies widely 3.5-8.5 lumens/watt.
Radio Shack 276-087A 6-7 lumens/watt. 7-8 degree beam 2 candela.
> Chicago Miniature CMD53SRC/E, approx. 8-8.5 lumens/watt. (October 1997)
Chicago Miniature CMD53SRD/G, approx. 8.5-9 lumens/watt. Claimed 1000 mcd 60 degree beam but I found the beam to be narrower. Consistency was notably and unusually good. (October 1997)
AND's AND180HRP 8-8.5 lumens per watt. Claimed peak wavelength 644 nm, approx. dominant wavelength 632 nm. Newark Electronics catalog number 92F2646.
Toshiba TLRH190P (untested) presumed similar in color and efficiency. 10 mm jumbo, claimed brightness 15 candela, Hosfelt catalog number of 25-339, price US$ 3.49 according to their 2000-A catalog.

Others with luminous efficacy around 8 lumens/watt or less:

Panasonic LN261CAL(UR)/Digi-Key P408ND
Toshiba TLRA191P / Hosfelt Electronics cat. no. 25-246.
Toshiba TLRA180AP / Hosfelt Electronics with cat. no. 25-249.
Electronic Goldmine G9601, approx. 5 lumens/watt.

Most Efficient Red-Orange LEDs - 21-22 maybe now 28.5 lumens/watt by Agilent, 15 lumens/watt by Toshiba, soon 53 by Lumileds.

UPDATE 7/5/2001 - I just got some datasheets from Lumileds on their Luxeon series that is about to go into production. The "high dome" red-orange Luxeons will supposedly produce 39.8 lumens minimum, 55 lumens typical at 350 mA with a 2.95 volt typical voltage drop. This is 38.5 lumens/watt minimum (assuming the typical voltage drop), 42.6 lumens/watt typical. I expect overall luminous efficacy to be even a little higher at somewhat lower currents around 200 mA. I am guessing that this model uses those truncated inverted pyramid dice mentioned above.

The "Low Dome" is not as efficient (typically 25 lumens/watt at 350 mA, probably more at 200 mA) and produces less light. My guess is that the high dome but not the low dome use truncated inverted pyramid dice.

UPDATE 8/29/2000 - Lumileds HPWT-PH00, formerly a Hewlett Packard part number, datasheet at

. This datasheet says 3.75 lumens typical at 70 mA with a 2.5 volt voltage drop which works out to 21.4 lumens/watt.

UPDATE 9/4/2000 - The above datasheet has a set of curves that indicates light output at 25 mA is about 44 percent of that at 70 mA. I think these curves are a bit off in the low current end (I know efficiency actually decreases as current is decreased to just a few mA) but it seems reasonable to expect 40 percent of the 70 mA light output at 25 mA. The voltage drop at 25 mA is 2.1 instead of 2.5 volts, so you get 40 percent of full light at 30 percent of full power. 4/3 of 21.4 is 28.5 lumens/watt.

There are even greater red-orange LEDs at Lumileds - the HPWS-FH00 and the HPWS-TH00. According to the datasheet linked just below, the standard grade produces 6 lumens minimum and the highest projected-available grade (HPWS-FH00-N4000 and HPWS-TH00-N4000, supposedly available 2002) supposedly will produce 10 lumens minimum at 150 mA with a typical forward voltage drop of 2.55 volts. The high grade figures work out to 26.1 lumens/watt minimum and the 2000-available standard grade works out to 15.7 lumens/watt minimum. I expect significantly higher efficiency at currents below the 150 mA maximum, such as 60-110 mA. Now for the datasheet:

As for a T1-3/4 / 5 mm. model Agilent model? This is the HLMP-DH16 and related models. My tests indicate an overall luminous efficacy ranging from 17.5 to 22 lumens/watt. The HLMP-DH16 supposedly has a 4000 mcd 15 degree beam.
For info on bright orange Agilent LED lamps check out the Agilent links above.

Note that many of these LED lamps are sorted into brightness grades with different suffix portions of the part number.

UPDATE 8/20/2000 Agilent's HPWT-BH00-00000, HPWT-DH00-00000, HPWT-MH00-00000, and HPWT-RH00-00000 are very reddish orange (more like orange-red) "AutoLEDs" of color good for taillights. Agilent's data sheet claims a typical light output of 3.75 lumens for 70 mA with a typical voltage drop of 2.5 volts. This is 21.4 lumens per watt! Overall luminous efficacy is probably maximized around 24 lumens/watt at lower currents around 20-40 mA.

UPDATE 3/16/2000 - Hosfelt Electronics 25-359, Toshiba TLSH180P tests as 15-16 lumens/watt. Hosfelt mentions it as red but I found it to be a very red orange. Beam is 6-8 degrees and 8 candela at 20 mA.

Toshiba's TLOA190P(WX) is a 10 mm diameter jumbo orange LED with an overall luminous efficacy of roughly 14 to maybe 15 lumens per watt. These are available from Hosfelt Electronics, catalog no. 25-276, price US$ 3.49 each according to Hosfelt's 2000-A catalog. They have a very narrow main beam that is roughly 2.4 degrees square with a dim spot in the center (my finding). The beam brightness at 20 mA seems to meet the claim of 36 candela.

Radio Shack's 276-206 10 mm jumbo has an overall luminous efficacy of roughly 12-13 lumens per watt. It has a somewhat irregular main beam that is roughly a 2.5 by 3.7 degree rectangle with a claimed brightness of 12 candela at 20 mA.

Other orange models worth mentioning:

Toshiba TLOA180AP, 10-11 lumens/watt, and supposedly have 3 candela, 18 degree beam, Hosfelt Electronics Cat. # 25-277, US$ .75 according to their 2001-A catalog.

Note that the above orange LEDs have a red-orange color, with dominant wavelengths generally around 610 to 617 nm. Some of these sometimes look more red than orange. Some LED lamps in this color class are red enough to be used for automobile tail lights!

Most Efficient Truly Orange LEDs - 18-22 lumens/watt by Toshiba, 18-21 lumens/watt by Agilent.

UPDATE TESTED 5/27/2001 - Toshiba TLOE20T, Hosfelt Electronics 25-407, $1.45 as of the 2001-A catalog, two pieces tested at 18 and 22 lumens/watt! Dominant wavelength 605-608 nm slightly reddish orange. Claimed brigtness 10 candela.

Agilent has the HLMP-DJ** LEDs, which are truly orange. The dominant wavelength is supposedly 605 nm, which is about that of an NE-2H neon lamp, and less red than the color of most other orange LEDs. The HLMP-DJ08 supposedly has a 9.5 candela 6 degree main beam.

RE-TESTED 5/27/2000 - HLMP-DJ24, 18-21 lumens/watt! I did say 16-19 before. The color was extremely slightly more red than that of an NE-2H neon lamp and much less red than that of other orange LEDs. I got these from Newark Electronics. The HLMP-DJ24 is a 23 degree model with a typical beam intensity of 2 candela.

Also note that these brightest HLMP-D*** part numbers are obsoleted and the current ones have HLMP-E*** part numbers. Look in:

Agilent Orange-Red, Reddish Orange, Orange and Amber "Sunpower" LED Lamps of beam angles 6, 15, 23, and 30 degrees.

Most Efficient Yellow / Amber LEDs - 14-16 lumens/watt by Toshiba, Marktech and maybe AND, 13 to maybe 14.5 by Agilent, soon 34-35 by Lumileds with 20-21-plus known achieved.

UPDATE 7/5/2001 - I just got some datasheets from Lumileds on their Luxeon series that is about to go into production. The "high dome" "amber" Luxeons will supposedly produce 23.5 lumens minimum, 36 lumens typical at 350 mA with a 2.95 volt typical voltage drop. This is 22.7 lumens/watt minimum (assuming the typical voltage drop), 34.8 lumens/watt typical. I expect overall luminous efficacy to be even a little higher at somewhat lower currents around 200 mA. I am guessing that this model uses those truncated inverted pyramid dice mentioned above.

The "Low Dome" is not as efficient (typically 20 lumens/watt) and produces less light. My guess is that the high dome but not the low dome use truncated inverted pyramid dice.

UPDATE 7/23/2001 - TESTED - An older Lumileds prototype that a web site fan sent me, apparantly a prototype form of the LXHL-ML1D - "high dome" with the truncated inverted pyramid die. At 175 mA, voltage drop was 2.27 volts and light output was approx. 8-8.5 lumens, for an overall luminous efficacy of 20-21 lumens/watt.

UPDATE 5/27/2001 - TESTED - Toshiba TLYE20T, Hosfelt Electronics 25-408, $1.45 each in their 2001-A catalog, 2 pieces tested 14 and 15.5 lumens/watt. Claimed brightness 9.5 candela.

UPDATE 1/4/2001 - I just did tests on a Marktech 54E38xx (apparantly a Toshiba model) sent to me by Craig Johnson. My tests indicate a good 16 lumens per watt overall luminous efficacy by that sample. This seems to have about a 15 degree beam probably around 10 candela at 20 mA.

Another aparantly Toshiba model sent by Craig Johnson tested at 15 lumens/watt on 12/28/2000.

UPDATE 9/4/2000: Agilent's HPWT-ML00-00000 and related types may well typically get 14.5 lumens/watt at 25 mA as well as 11 lumens/watt at their maximum current of 70 mA. Typical light output is 2 lumens at 70 mA and probably .8 lumen at 25 mA. Typical voltage drop is 2.6 volts at 70 mA and 2.2 volts at 25 mA. For more info, look in this PDF datasheet:

This sheet shows curves for light output as a function of current. They show 44 percent of the 70 mA value at 25 mA but I think they are a bit optimistic on low current and I think more like 40 percent at 70 mA. These LEDs have efficiency actually decrease when current is reduced to a few mA.

Agilent's "amber" HLMP-DL16 has an overall luminous efficacy of about 13 lumens per watt accodring to my tests. This is a 5 mm. model with a supposedly 4.5 candela 15 degree beam.
For info on current Agilent / HP LED lamps of this general type, check out the Agilent links above.

Note that at least some of these come in 2-3 brightness sorted subtypes with different suffix portions of the part numbers.

There are amber "autoLEDs", HPWT-DL00 and HPWT-ML00. The data sheet works out 11 lumens per watt for a typical overall luminous efficacy. The typcal light output is supposedly 2 lumens at 70 mA and the typical voltage drop at 70 mA is supposedly 2.6 volts. Overall luminous efficacy is probably maximized closer to 13 lumens/watt at lower currents of 20 to 40 mA.

Other notable yellow LEDs:

Toshiba's TLYH180P and the suspiciously similar AND AND180HYP both have luminous efficacy around 11 lumens/watt and 8 candela 6-8 degree beams.

Agilent HLMP-DL08 and HLMP-DL10, 9500 mcd 5 mm. lamp size, probably around 11 lumens/watt.
Toshiba TLYH190P, supposedly 23 candela beam which is about 2.4 degrees roughly square. Hosfelt Electronics catalog no. 25-342, $3.49 according to the 2000-A catalog. Overall luminous efficacy only about 6 lumens/watt.

Radio Shack wide angle yellow LED lamp 276-302, approx. 10 lumens/watt. 500 mcd 40 degree beam. Very orangish amber-yellow, dominant wavelength approx. 594 nm.

Radio Shack 276-301, roughly 6 degree square beam with a dim spot in the center (my findings), a few thousand mcd, approx. 7 lumens/watt. Very orangish amber-yellow, dominant wavelength approx. 594 nm.

Radio Shack 276-350 widebeam yellow 5 mm lamp - preliminary findings of 5.5-6 lumens per watt overall luminous efficacy.

Radio Shack 276-205 10 mm jumbo, about 4-5 lumens/watt. The beam is irregular and roughly a 2.5 by 3.7 degree rectangle and supposedly 6 candela.

Most Efficient Yellow-Green LEDs - 3-4 lumens/watt by Toshiba and AND, but there is a way to get 20-40.

Some Toshiba LEDs and AND ones that look like Toshibas have an overall luminous efficacy around 3-4 lumens per watt. These are very yellowish green LEDs with a dominant wavelength around 570-573 nm:

Toshiba TLGA183P, Hosfelt Electronics catalog number of 25-341, US$ .99 according to their 99-B catalog, beam approx. 7-8 degrees, claimed brightness 3 candela.

AND's AND183HGP, Newark Electronics catalog number 92f2644.

UPDATE 9/7/99 - Toshiba TLGE185EP, Hosfelt Electronics 25-366 has a better defined beam of supposedly 3.5 candela (I think 2-2.5) and maybe about 15 degrees but no higher efficiency. $.99 from Hosfelt with a catalog number of 25-366 according to their 2000-B catalog.

LEDs of similar color but with overall luminous efficacy slightly higher than that of white ones can be made by suitably adding a suitable fluorescent dye to white or blue ones. That means about 20 lumens/watt! The Cree "Mega Bright" blues combined with green-fluorescing yellow material may get 40 lumens/watt! If you put a white or blue LED into a piece of green-fluorescing yellow acrylic this will probably work! Go Here for LED Hacking for Fun and Danger.

Most Efficient Green LEDs - 25-maybe 32 lumens/watt average and sometimes 40 by Nichia, 15-16 (maybe now more) by Toyoda Gosei and maybe Agilent.

UPDATE 4/30/2001 TESTED 10 pieces of Nichia NSPG-500S of brightness rank T (supposedly typically 14 candela) - 39 lumens/watt average!

Optical output ranged from 5.05 to 5.7 mW, averaging 5.4 mW at 20 mA. Voltage drop at 20 mA was 3.4 volts - conversion efficiency was 7.4 to almost 8.4 percent, averaging 7.9 percent. These LEDs had a slightly yellower shade of green than average for color rank G Nichia green (525 nm dominant wavelength) - estimated luminous efficacy of the emitted light was 500 lumens/watt (SUBJECT TO RE-EVALUATION (this note added 5/2/2001) - may require slight adjustment). This works out to an overall luminous efficacy of 37 to nearly 42 lumens/watt, averaging about 39.
YOUR MILEAGE MAY VARY both in conversion efficiency and in the luminous efficacy of the emitted light - my judgement is be prepared for (my guesstimate) anything in the 30's to mid 40's lumens per watt of overall luminous efficacy from top-of-the-line current production Nichia green LEDs obtained from Nichia sales offices!

UPDATE 1/15/2001:

I continue to occaisionally order green Nichia LEDs to test, mostly Hosfelt 25-377 and BG Micro LED-1050. Results below are for these as well as a few that I ordered from a Nichia sales office.

UNITS FROM A NICHIA SALES OFFICE October 1999 - four NSPG-500S (5 mm 15 degree beam) pieces tested as ranging from 4.6 to 5 mW optical output at 20 mA. Estimated luminous efficacy of the emitted light 480-500 lumens/watt. Overall luminous efficacy was estimated to be 32-37 lumens/watt. Someone I contacted mentioned that this batch was above-average - typical output at 20 mA for an average piece was supposedly 4 mW with overall luminous efficacy of 25 lumens/watt.

HOSFELT ELECTRONICS (1-800-524-6464) 25-377, from three different orders at various times from mid-March to early December 2000, totalling 14 pieces tested. Two from July 2000 appeared to be Nichia NSPG-520S (45 degree beam) and the other 12 appeared to be Nichia NSPG-500S. Optical output at 20 mA ranged from 3.7 to 6.35 mW, with an average of about 4.6 mW. Luminous efficacy of the emitted light was estimated to mostly be 440 to 480 lumens per watt. Overall luminous efficacy with these estimates ranged from 25 to 40-41 lumens per watt, with the average being about 31 lumens/watt. The most efficient ones of these that I have tested were the two July widebeam pieces.

BG MICRO (1-800-276-2206) LED-1050 - 58 pieces tested from three batches ordered from BG Micro at various times from early July to late December 2000 plus a loaner from Craig Johnson. Two "duds" in one batch put out an estimated 3-3.3 mW at 20 mA while the other 56 of these 58 put out 3.95 to 5.95 mW at 20 mA.
The two "duds" had a lime-green color and I estimated the luminous efficacy of their emitted light to be around 540-550 lumens/watt for an estimated overall luminous efficacy of around 24-25 lumens/watt.
The better 56 of these 58 pieces were estimated to have overall luminous efficacy ranging from 27 to 39 lumens/watt.

Voltage drop at 20 mA was mostly 3.45-3.5 volts. Estimated luminous efficacy of the emitted light was mainly 450-475 lumens per watt, maybe as low as 420-440 for the bluest one and as high as 520-525 for one that was noticeably more of a lime green than the other 55 of the 56 good pieces. There was a slight tendency for optical output to be higher among the more-blue-colored pieces and lower among the less-bluish pieces.

Nichia has improved their LEDs without changing the basic part numbers. The better ones are probably best obtained from Nichia sales offices.

UPDATE 5/27/2001 - Toyoda Gosei has improved versions in the works. If this is their only improvement since they made the ones below, then their greens should soon get about 21 lumens/watt. But I think this is an underestimate since they probably already had improvements since 1999.

UPDATE 10/15 and 10/31 /99 - All Electronics (1-800-826-5432) LED-57 green apparantly by Toyoda Gosei, 16 lumens/watt, 45 degree widebeam.
Craig Johnson reports that what I got is different from an LED-57 which he received, which appeared to be a Nichia model.

Cree is making ultrabright green LED dice (chips), but not as bright and efficient as those of Nichia. Cree has two efficiency classes and two chip size/current classes for at least one efficiency class in most colors/wavelengths including green.

Nichia Green LEDs get 30-55 lumens/watt at 5 milliamps

Update 7/20/2000 - See my note below on efficiency of indium gallium nitride LEDs at reduced current.

UPDATE 7/18/2000 - Most of my better Nichia NSPG-500S pieces had 50 percent higher overal luminous efficacy at 5 mA than at 20 mA, generally 48-55 lumens/watt. My remaining not-so-good BG Micro piece had a smaller efficacy increase of about 40 percent - the "duds" would get about 35 lumens/watt at 5 mA, at least 30.
Typical optical power output at 5 mA is 32 percent of that at 20 mA. Typical light output (in photometric units) at 5 mA is 35 percent of that at 20 mA - the additional improvement is due to a spectral shift towards the more visible yellow-green. The voltage drop is .2-.25 volt less at 5 mA than at 20 mA.

Most Efficient Blue-Green LEDs - 25 lumens/watt by Nichia, soon 25 by Lumileds (Toyoda Gosei, Cree, and Agilent are also in this game).

UPDATE 7/30/2000 - TESTED BG MIcro LED-1052 narrowbeam bluish green Nichia NSPE590S - preliminary figure 24-26 lumens/watt on the single sample ordered. This model has an irregular beam with a small central bright pattern (roughly 7 by 4 degrees) with a claimed typical brightness of 20,800 mcd at 20 mA.

TESTED Hosfelt Electronics 25-376, apparantly a Nichia model. Tentative figure for overall luminous efficacy 24-27 lumens/watt. Optical power output 7 mW at 20 ma with a 3.75 volt voltage drop - 9.3 percent conversion efficiency! Expect even better efficiency in the future since the voltage drop will usually be 3.5-3.6 volts.

Agilent / Hewlett Packard is now making bluish green LEDs suitable for traffic signals - HP Introduces "Traffic-Signal Green" LEDs, Becomes First "All Color" LED Supplier For Traffic-Signal OEMs. Cree is making ultrabright 505 nm bluish green LEDs, but not as bright and efficient as those of Nichia.

UPDATE 7/5/2001 - Lumileds will soon have their "Luxeon" series of high power LEDs. The blue-green ones are expected to typically produce 30 lumens of light at 350 mA with a typical forward voltage drop of 3.42 volts, for a typical overall luminous efficacy of 25 lumens/watt. Overall luminous efficacy will be even higher at lower currents. I expect typically at least 35 lumens per watt at 50 mA.

Most Efficient Blue LEDs - 7.5-8, rarely 10 lumens/watt by Nichia, ~5.5-plus by Toyoda Gosei, and probably Agilent / Hewlett Packard, soon 9-plus by Lumileds, soon 12 by Cree.

UPDATE 8/28/2001 - Cree has on their website a PDF Datasheet for their Mega Bright Blue LED dice / chips. According to this datasheet, typical luminous output is .88 lumen at 20 mA with a typical voltage drop of 3.6 volts. This works out to 12.2 lumens/watt.
Typical conversion efficiency is nearly 14 percent for the 470 nm version and a little over 15 percent for the 460 nm deep blue version.
Cree sells dice (chips) and not LED lamps (whole, ready-to-use LEDs).

UPDATE 7/4/2001 TESTED a blue Luxeon sample from Lumileds that I managed to get from an industry insider fan of this website.
Conversion efficiency was 16 percent at 40-50 mA and 13.3 percent at 170 mA (68 milliwatts optical output!). This was "Royal Blue" (deeper shade of blue than usual, dominant wavelength approx. 455 nm) rather than regular blue. Overall luminous efficacy was approx. 8 lumens/watt at 40-50 mA and around 6 lumens/watt at 200 mA. Royal blue will have greater "blue impact" than regular blue in RGB devices.

UPDATE 7/5/2001 - I got a set of Luxeon datasheets claiming minimum 8.2 lumens, typically 11 lumens for blue (dominant wavelength 470 nm) at 350 mA with a typical voltage drop of 3.42 volts. This is a minimum of 6.8 lumens per watt and typically 9.2 lumens per watt assuming 3.42 volts at 350 mA. Overall luminous efficacy will almost certainly be substantially higher at lower currents, peaking somewhere around 50 mA.

MINOR UPDATE 6/25/2001: Radio Shack 276-316 blue:

Claimed 2600 mcd 30 degree beam. Beam angle is definitely around 18 degrees and not 30, and the beam is more like an 8 degree beam in a 16-18 degree ring than a solid 18 degree beam. Photometric results - around 1-1.5 lumens/watt overall luminous efficacy. The chip is apparantly a somewhat-below-average Cree C470-CB290-E1000. This paragraph will be moved to a location lower in this "blue section" sometime in December 2001.

UPDATE 4/30/2001 - TESTED - Nichia NSPB-500S of Brightness Rank T (extra-high) - at least 7.7, maybe 8 lumens/watt!

Optical output was surprisingly consistent, within a 3 percent range, averaging at least 7.4 mW at 20 mA, probably more since my solar cell probably has less quantum efficiency in the blue than from green to near-IR. Voltage drop at 20 mA was 3.6 volts. Conversion efficiency was a good 10.3 percent and probably a little more. The color was a slightly greener than average blue for Nichia's color rank W (usual blue, typical dominant wavelength 470 nm), so I estimated the luminous efficacy of the emitted light to be 75 lumens/watt. Overall luminous efficacy would then be a good 7.7, maybe 8 lumens/watt. YOUR MILEAGE MAY VARY!

UPDATE 5/16 and 5/1 2001 - I have some Nichia NSPB-500S pieces of their color ranks V (deeper blue, dominant wavelength around 460 nm) and X (greenish blue, dominant wavelength in the upper 470's). The V pieces had conversion efficiency averaging at least 10 percent with some around 11 percent. The X pieces got about 11 percent, and they were of the extreme brightness rank of U (typically 6 candela for NSPB-500S) which only the X color rank of Nichia blue achieves. The XU pieces in my hands got 9.5-10 lumens per watt of overall luminous efficacy. Note that Nichia blue LEDs of color rank other than the usual W have experienced low and spotty production, are not always in stock at Nichia sales offices, and are in danger of being discontinued. Figures here are for use at 20 mA and expect about 30 percent more efficiency and 40 percent more overall luminous efficacy at 3-4 mA.

Nichia blues of their usual color rank W should occaisionally now achieve 11 percent conversion efficiency which is good for about 8 lumens per watt of overall luminous efficacy.


Notably, Nichia NSPB-500S pieces of color rank W (the usual one) obtained from BG Micro, catalog number LED-1051. Based on three separate orders in the second half of 2000, I was getting average overall luminous efficacy of at least 6.5 lumens/watt. The worst piece was about 5.5-6 and the best was about 7.5 lumens/watt, possibly approaching 8 lumens/watt.

Agilent claims that typical luminous efficacy of the emitted light of their blue LEDs of 470 nm peak wavelength and 472 nm dominant wavelength is 75 lumens per emitted watt. The typical figure for Nichia blue LEDs of their usual color rank W is probably slightly less - I assume 70.

NOTE - Nichia's official figure for typical optical output power of their blue LEDs at 20 mA is 6 mW as of June 2000. With a typical voltage drop of 3.5 volts and luminous efficacy of the emitted light assumed to be typically 70 lumens/watt, the typical overall luminous efficacy would be 6 lumens/watt.

TESTED UPDATE 7/12/2000 - Radio Shack special-order item 900-8005, 2 pieces, apparantly Nichia NSPB-500S which contradicts the catalog claim of 450 nm blue, one approx. 6 lumens/watt with the other approx. 7 lumens/watt.

Toyoda Gosei 15 degree models with really impressive beam candela figures have a ring-plus-blotch pattern rather than a more solid beam.

Agilent is now making 470 nm blue LEDs. So is Panasonic, and someone told me they are using Toyoda Gosei chips.

Panasonic 470 nm blue LEDs are now available from Digi-Key.

Radio Shack's 276-311 blue LEDs and other 430 nm blue LEDs are nice and actually close to "high brightness", but are not nearly as bright as others mentioned here. Some of these are referred to as 466 nm blue LEDs since Cree, the manufacturer of the chip, specifies the dominant wavelength at 466 nm. The largish spread between peak and dominant wavelengths is a result of spectral distribution being a narrow violet-blue peak combined with a very broad band that separately would be green-bluish white. These LEDs glow with a whitish non-turquoisish, maybe slightly violetish blue. The Cree blue chip used in these is their C430-CB290-E1000, or "standard blue".

Most Efficient White LEDs - 15-16 sometimes 18 lumens/watt by Nichia, 10-plus by others such as Agilent, soon 15 by Lumileds, maybe soon 20-25 for ones with newer Cree chips.

UPDATE - Cree "Mega Bright" 470 nm blue dice have typical optical output of 10 mW at 20 mA, which is an improvement over comparable Nichia ones that I have seen (8 mW at 20 mA for better ones as of early 2001). I have yet to see any white LED lamps using these new Cree dice.

UPDATE 4/24/2001 - Lumileds is about to produce their "Luxeon" series high power LEDs on heat-sinking boards which include white ones that have typical overall luminous efficacy of 15 lumens per watt (18 lumens at 350 mA with a typical voltage drop of 3.42 volts).

UPDATE 7/31/2000 and 9/26/2000 TESTED Radio Shack 276-320 two pieces. Preliminary figure 14-16 lumens/watt. Beam is supposedly 100 degrees but looks more like 60. Rated candela is 1.1. The package says made in China but the guts appear to be Nichia. The beam has a blue ring within the broader blurred white beam, worse than usual for white LEDs that are known to be made by Nichia as opposed to maybe someone else using Nichia chips and leadframes. The color overall seemed more blue or violet-blue than usual, with color temperature estimated 7500K for one and 8000K (maybe more) for the other.

UPDATE 9/26/2000 re-evaluation, original preliminary tests 7/22/2000:

Tested: five white BG Micro LED-1044 pieces, apparantly Nichia NSPW-500BS. Preliminary UPDATED results: 11, 16, 16, 18, and 18 lumens per watt at 20 mA. The 11 I consider a dud and the average of the others is 17.

UPDATE 10/31-99 - Nichia NSPW-500BS models ordered mid-october 1999 test as 15-16 lumens/watt at 20 mA, meeting their mid-1999 claim of 15 typical. The current NSPW-500BS nominally has a 5.6 candela 20 degree beam.

UPDATE 9/14/99 - Hosfelt Electronics 25-363, which is apparantly a Nichia model with a claimed brightness of 4 candela. It tested at 10-11 lumens/watt.

Hosfelt Electronics 25-367 is very nearly as efficient as the 25-363, but has a style of the internal portion of the leads and an aqua-ish blue chip color at low current both like Toyoda Gosei instead of Nichia. I am not sure of the manufacturer although Toyoda Gosei is not yet making white LED lamps. This is a 10 mm. lamp with a supposedly 7 candela 10 degree beam. I think that 7 candela is achieved in a noticeable, very bluish and bright ~5 degree central hot spot. Outside this bluish hot spot, the beam is non-bluish white and nowhere near 7 candela. Seems about 9, possibly 10 lumens/watt at 20 mA with good prospects of higher efficiency at a few mA.

The above white LED lamps have blue chips plus a phosphor to convert some of the blue light to yellow light of broadband spectral content from mid-green to mid-red. The color is usually a cool "daylight" slightly bluish or sometimes violetish-bluish white, usually of about 6000-6500 K.

General info on Nichia LEDs:

All of my Nichia info I moved to a separate document

This includes some suppliers of white, blue, and green LEDs that appear to use Nichia's technology.

Increased Efficiency of InGaN LEDs at lower currents

UPDATE 7/20/2000 - I see a trend that InGaN green, blue-green and blue LEDs (465-530 nm or so, and at least the non-Cree ones) have about 32 percent as much optical output at 5 mA as at 20 mA. In addition, there is usually a spectral shift towards longer wavelengths closer to the visibility peak of 555 nm, which results in more lumens and more candela per milliwatt of optical output. The voltage drop is also .2-.25 volt less at 5 mA than at 20 mA. Overall luminous efficacy will generally be about 50 percent more at 5 mA than at 20 mA.

Efficiency continues to increase with decreasing current at least down to 4 mA and is close to peak around 2 mA and remains above the 20 mA efficiency at least down to .5 mA. Efficiency and light output become less predictable below .4 mA.

White LEDs have most of their photometric output from a phosphor, and so the luminous efficacy of emitted light does not improve with decreasing current as much as with colored InGaN LEDs. In fact, spectral shifting of the LED chip's output away from wavelengths best-utilized by the phosphor can impair overall luminous efficacy at low currents. However, photometric output per milliamp seems to usually improve with decreasing current down to about 4 milliamps. No solar cell measurements on white ones at low current yet, but I think output at 5 mA should be 30-32 percent of that at 20 mA for an overall luminous efficacy of 1.25 to 1.35 times that at 20 mA.

Important Notes on Gallium-Nitride LEDs!
1) Blue, blue-green, bright non-yellowish green, and other gallium nitride and indium gallium nitride type LEDs have a voltage drop around 3-4 volts, usually 3.4-3.6 volts at 20 mA, higher than the 1.6 to 2.4 volts typical of other colors.
2) Gallium nitride and indium gallium nitride LEDs are fussy, and do not like their ratings to be exceeded. Exceeding 5 volts reverse voltage even with low current is supposedly damaging to them. I suspect that destructive electrolysis is what goes wrong. Peak forward currents in excess of 100 mA may also be bad. These LEDs are also supposed to be considered static sensitive.

Photon brand "Micro Lights" Keyring LED flashlights

Available at Hosfelt Electronics - in 7 colors:

red - 25-292 ($10.95)
orange - 25-354 ($14.95)
yellow - 25-291 ($10.95)
green - 25-333 ($14.95)
turquoise - 23-355 ($14.95)
blue - 25-332 ($14.95)
white - 25-331 ($14.95)

High candela (beam candlepower) LEDs

Toshiba TLOH190P, see above in Orange LEDs. 18 to 36 candela at 20 mA and I think 36.

Brightest 5 mm LED lamp - the blue-green Nichia NSPE-590S, typical beam candela 20.8 for ones manufactured around or since late 1999. The bright central portion of the beam is a "dumbbell" of two squares attached at the corners, with overall angular dimensions of roughly 4 by 7 degrees. The two squares are maybe 2.5-3 degrees wide.

Agilent has bright T1-3/4 (5 mm.) orangish red, red-orange and orange models with 6 degree beams and brightness 8 candela minimum 31 candela maximum at 20 mA (for the brightest bin sort subtypes).

Look in the Agilent links towards the top of this document.

LED Lamps with High Total Light Output

If you want more LED light from a small source than is available from any of the champions described elsewhere above, there are the LED cluster lamps made by Opto Technology. These include miniaturized cluster lamps in heat sinkable TO-66 packages that can take 8-10 watts and emit high total luminous flux quantities like around 50 lumens. They have other products and do custom jobs also!

Then there is Lumileds, a joint venture of Agilent and Philips Lighting. They have some bright ones and some doozies, mainly in in the fields of automotive lights and traffic lights for now but this will expand.

As for one basic LED lamp (single "bulb" unit) production line of theirs, they have one series with blue-green units producing up to 25 lumens from only about 1.25 watts!

Details in this 11/03/2000 Press Release!

Notes on Where To Get Bright LEDs

Some Agilent, Chicago Miniature, and most AND (apparantly Toshiba) LEDs are available from Newark Electronics. Call 800-4NEWARK or visit http:/ They are in a position to collect sales tax if you live in or order from any U.S. state with a sales tax. Minimum order is US$ 25. In addition, the minimum order for most Chicago Miniature Lamp items is 10 pieces of each type. Shipping is extra and duplicate shipping charges apply if you order more than one type of item not all in stock in the same warehouse. Higher minimums may apply to non-stock merchandise - often 500 pieces of any non-stocked Agilent LED lamp, and this applies with most other Agilent distributors as well.

You can see what Agilent LED lamps are in stock at Newark (and even order online) through Agilent Small Quantity Ordering from Newark Electronics.

Hosfelt Electronics sells some bright Toshiba LEDs and some other interesting LEDs.

Phone: 800-524-6464, 888-264-6464, 614-264-6464
FAX: 800-524-5414, 614-264-5414
Orders shipped to Ohio addresses subject to 6.5 percent sales tax. No minimum order for prepay or credit card orders, shipping is extra. Prepay orders must include $6.50 for shipping, any excess will be refunded. Some items mentioned on this web page may be out of stock or discontinued - check with Hosfelt, not me for stocking status.

Hosfelt has some typo errors - some blue LEDs have lowish supposed voltage drop figures like 2.6-3 volts, but expect about 3.5 volts at 20 mA. Some strange beam angle figures have appeared in their web site and some of their catalogs - 29.5 and 28.5 degrees. Possibly someone saw the "two-theta-half" symbol which resembles 28 1/2 as the actual number of degrees. These look like typos, maybe on the part of a datasheet from a supplier, and are not attempts on Hosfelt's part to give falsely optimistic specifications.

Michael W. Sforza's Custom Model Light Service (e-mail also sells bright LEDs. Stock is limited, selection is limited but growing, and prices seem reasonable. E-mail for prices and inquiries. This business specializes in sales of smaller to medium quantities of LEDs and customized addition of lights to building, railroad, vehicle and other models.

I have info on a few Nichia sales offices in a separate document.

Toyoda Gosei makes bright green and blue LEDs.

Toyoda Gosei LED info is now on the web at

LEDSaurus is a teeny little LED mail order outfit with an online catalog.

UPDATE late on 9/9/2000 - LEDSaurus now accepts credit cards (via PayPal) in addition to checks and money orders.

Some brighter LEDs are available. Stock is limited. Prices are reasonable for hobbyists and there is no minimum order. Get what they have while you can!

Jade Mountain ( sells white LEDs (probably Nichia) as well as lighting products using this LED and other energy-saving lighting products. But I believe some of the energy efficiency and light output claims for their white LED products to be very unrealistic. These white LEDs are only about as efficient as better incandescent lamps and average halogen lamps at best, maybe slightly better than this at below-typical per-LED operating power less than .07 watt per LED. Their catalog number for the white LED is DC5206 and the price was $2.00 each plus shipping as of 5/2/2001.

Converting / comparing lumens, candelas, millicandelas

Many people ask what are lumens, lumens/watt, candelas, and millicandelas and how to convert among these units.

A lumen is a unit of light output, equal to 1 / (60 * pi) of the light emitted by one square centimeter of ideal blackbody surface at the melting point of platinum.
When the spectrum differs from that of a blackbody at the melting point of platinum, equate lumens by applying the official photopic function to the quantity of light at every wavelength present. One watt of light at any single wavelength (or in a very narrow band) is, in lumens, 681 times the official photopic function of that wavelength. Any eyeballs (or other light sensors) of spectral response deviating from that of the "official standard observer" could see as unequally bright light sources of equal lumens/candela and different spectral output.

A "USA-usual" 100 watt, 120 volt, 750 hour "regular" (A19) lightbulb usually produces 1710 lumens.

Lumens per watt is a measure of efficiency in converting electrical energy to light. Multiply this by the watts dissipated in the LED to get lumens. A typical red, orange, or yellow or yellow-green LED has a voltage drop around 2 volts and is getting around .04 watt at the typical "standard" current of 20 milliamps. A blue, white, or non-yellowish-green one typically has a voltage drop of 3.4 volts at 20 mA and gets .068 watt at 20 mA.

A candela is a lumen per steradian, or "beam candlepower". The candela is a primarily defined metric unit, equal to 1/60 of the perpendicular/normal "candlepower" of one square centimeter of ideal blackbody surface at the melting point of platinum.
So lumens are candelas times the beam coverage in steradians. Candelas are lumens divided by the beam coverage in steradians. Ideally, that is - assuming that all light is within the beam and the "candlepower" is constant within this beam.

So you may now be wondering what a steradian is. It is 1 / (4 * pi) of a whole sphere or 1 / (2 * pi) of a hemisphere or about 3283 "square degrees". To get steradians from the beam angle:

Steradians = 2 * pi * (1 - cos (.5 * (beam angle)))

(NOTE: There are a few other expressions equal to this. Proving that is homework for 12th graders taking trig / "elementary functions".)

So if you determine the steradian beam coverage and multiply that by the candela figure (or 1/1000 of the millicandela figure), you get the lumen light output - very roughly! The beam is not uniform and it does not contain all of the light. Obtaining lumens from beam angle and candela can easily be in the +100 / - 50 percent range. Actual lumens are generally higher than predicted by this formula with smaller beam angles of 8 degrees or less since the nominal beam does not include a secondary "ring-shaped" "beam" that usually surrounds the main one. Also note that some beam angle figures are optimistic and could lead one to expect a lot more lumen light output than actually occurs.

If you know of anything worth adding to this site, please e-mail me.

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