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Don Klipstein
Guest
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 Posted:
Mon Nov 28, 2005 11:59 pm Post subject:
Re: LED brightness? |
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In article <op.s0htdnilwabk2w@blue.mshome.net>, Peter Hucker wrote:
| Quote: | I'm wanting to purchase bright LEDs, but am confused by the specs.
Am I correct in the following assumption?
A 100mcd LED with a viewing angle of 30 degrees will light the surface
in front of it at the same brightness as a 100mcd LED with a viewing
angle of 15 degrees, but will light a larger area, therefore is giving
off more light in total.
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Correct!
- Don Klipstein (don@misty.com)
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Don Klipstein
Guest
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| Posted:
Tue Nov 29, 2005 12:03 am Post subject:
Re: LED brightness? |
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In article <1ljun19ho2m9a60vbg1m55hv7t2vfj5kt5@4ax.com>, John Fields wrote:
| Quote: | On Sat, 19 Nov 2005 15:02:01 -0000, "Peter Hucker" <no@spam.com
wrote:
I'm wanting to purchase bright LEDs, but am confused by the specs.
Am I correct in the following assumption?
A 100mcd LED with a viewing angle of 30 degrees will light the surface
in front of it at the same brightness as a 100mcd LED with a viewing
angle of 15 degrees, but will light a larger area, therefore is giving
off more light in total.
---
No.
100 millicandelas is the total light output, so the area illuminated
by the LED with the larger beamwidth will be dimmer.
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Candela is not a unit of total light output, but of "beam candlepower".
1 candela illuminates a spot on a surface 1 meter away to the extent of 1
lux.
The units of total light output are "spherical candlepower" (candela
averaged over all directions, including directions into which no light is
sent), and the lumen. 1 lumen is the total light in a "solid angle" of 1
steradian (1/4-pi hemisphere) where the light has an intensity uniformly
of 1 candela. A "spherical candlepower" is 4-pi lumens, the output of a 1
candela omnidirectional source.
- Don Klipstein (don@misty.com) |
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Peter Hucker
Guest
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| Posted:
Wed Nov 30, 2005 1:35 am Post subject:
Re: LED brightness? |
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On Tue, 29 Nov 2005 00:03:43 -0000, Don Klipstein <don@manx.misty.com> wrote:
| Quote: | In article <1ljun19ho2m9a60vbg1m55hv7t2vfj5kt5@4ax.com>, John Fields wrote:
On Sat, 19 Nov 2005 15:02:01 -0000, "Peter Hucker" <no@spam.com
wrote:
I'm wanting to purchase bright LEDs, but am confused by the specs.
Am I correct in the following assumption?
A 100mcd LED with a viewing angle of 30 degrees will light the surface
in front of it at the same brightness as a 100mcd LED with a viewing
angle of 15 degrees, but will light a larger area, therefore is giving
off more light in total.
---
No.
100 millicandelas is the total light output, so the area illuminated
by the LED with the larger beamwidth will be dimmer.
Candela is not a unit of total light output, but of "beam candlepower".
1 candela illuminates a spot on a surface 1 meter away to the extent of 1
lux.
The units of total light output are "spherical candlepower" (candela
averaged over all directions, including directions into which no light is
sent), and the lumen. 1 lumen is the total light in a "solid angle" of 1
steradian (1/4-pi hemisphere) where the light has an intensity uniformly
of 1 candela. A "spherical candlepower" is 4-pi lumens, the output of a 1
candela omnidirectional source.
- Don Klipstein (don@misty.com)
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I purchased a range of LEDs and tested them. The mcd rating appears to be TOTAL light output.
--
http://www.petersparrots.com http://www.insanevideoclips.com http://www.petersphotos.com
The teacher in Johnny's school asked the class what their parents did for a living. One little girl said her father was a doctor, another said her mother was an engineer. When it was Little Johnny's turn, he stood up and said "My mom's a whore."
Naturally, after that remark, he got sent off to the principal'soffice. Then, 15 minutes later, he returned.
So the teacher asked "Did you tell the principal what you said in class?"
Johnny said "Yes"
"Well, what did the principal say?"
"He said that every job is important in our economy, gave me an apple and asked for my phone number."
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Don Klipstein
Guest
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| Posted:
Mon Dec 05, 2005 5:26 am Post subject:
Re: LED brightness? |
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In article <op.s00q9jr8wabk2w@blue.mshome.net>, Peter Hucker wrote:
| Quote: | On Tue, 29 Nov 2005 00:03:43 -0000, Don Klipstein <don@manx.misty.com> wrote:
In article <1ljun19ho2m9a60vbg1m55hv7t2vfj5kt5@4ax.com>, John Fields wrote:
On Sat, 19 Nov 2005 15:02:01 -0000, "Peter Hucker" <no@spam.com
wrote:
I'm wanting to purchase bright LEDs, but am confused by the specs.
Am I correct in the following assumption?
A 100mcd LED with a viewing angle of 30 degrees will light the surface
in front of it at the same brightness as a 100mcd LED with a viewing
angle of 15 degrees, but will light a larger area, therefore is giving
off more light in total.
---
No.
100 millicandelas is the total light output, so the area illuminated
by the LED with the larger beamwidth will be dimmer.
Candela is not a unit of total light output, but of "beam candlepower".
1 candela illuminates a spot on a surface 1 meter away to the extent of 1
lux.
The units of total light output are "spherical candlepower" (candela
averaged over all directions, including directions into which no light is
sent), and the lumen. 1 lumen is the total light in a "solid angle" of 1
steradian (1/4-pi hemisphere) where the light has an intensity uniformly
of 1 candela. A "spherical candlepower" is 4-pi lumens, the output of a 1
candela omnidirectional source.
- Don Klipstein (don@misty.com)
I purchased a range of LEDs and tested them. The mcd rating appears to
be TOTAL light output.
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Have you measured total luminous flux of a 15 degree model and a 60
degree model of the same millicandela, and known to actually be so?
Have you ever shone two LEDs of the same MCD, same color/wavelength and
same chip chemistry but greatly different beam wionto a solar cell and
measured short circuit current of the solar cell with a milliammeter?
(Comparison requires matching of spectrum because solar cells have
different spectral response than human vision has.)
Have you ever illuminated a dark room with two LEDs of greatly different
beam width and same MCD (and same color and wavelength and spectral
characteristics - night vision differs from "day vision" in a way that
varies with color/wavelength)?
I have been there and done that!
An ideal 1,000 millicandela beam that is 1,000 millicandela uniformly
within its specified boundary and completely lacking light outside it has
has .842 lumen of light if 60 degrees wide and has only .054 lumen of
light if 15 degrees wide. At least 15 degree and narrower-beam LEDs
usually have enough light outside their specified beams to get total light
output usually more than, sometimes by a factor of 2 more than, 2 times Pi
times (1 minus cosine of half the rated beam angular diameter).
- Don Klipstein (don@misty.com) |
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neon
Joined: 25 Feb 2006
Posts: 570
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| Posted:
Wed Jul 26, 2006 11:06 am Post subject:
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| guys they are the same output so why some are brighter ha!!!! i don't know maybe because i am looking at them directly move 15 to 30 degrees and see. THIS IS VERY BASIC |
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