R
Richard Crowley
Guest
"Bruce Murphy" wrote ...
OTOH, you can't argue with your own brain and iris.
C
crzndog
Guest
OK, what I was trying to say is the apparent brightness actually seems
brighter because there *is* saturation of the rods.
Now, with the eyes and the way in which the rods work, brightness is
actually a perception between the ilumnation of some rods versus other rods.
If most of the rods are in dakness and some of the rods are saturated, the
saturated rods will send the message to the brain that the light source is
very bright. With a larger dispersion of light (ie a wide beam) the
apparent brightness seems to be less as there is less of a distinction
between the rods.
Apparent brighness is the difference between 2 intensities. It is not
absolute.
"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:10q1riustd8ag8f@corp.supernews.com...
brighter because there *is* saturation of the rods.
Now, with the eyes and the way in which the rods work, brightness is
actually a perception between the ilumnation of some rods versus other rods.
If most of the rods are in dakness and some of the rods are saturated, the
saturated rods will send the message to the brain that the light source is
very bright. With a larger dispersion of light (ie a wide beam) the
apparent brightness seems to be less as there is less of a distinction
between the rods.
Apparent brighness is the difference between 2 intensities. It is not
absolute.
"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:10q1riustd8ag8f@corp.supernews.com...
C
crzndog
Guest
Agreed. Lumens over a certain angle also.
Spot lights and wide beam lights of the same lumens values will have a
different lighting effect. The light reflected will be more concentrated in
the narrower beam lights.
"Victor Roberts" <xxx@lighting-research.com> wrote in message
news:v3g1q0ddv5u9hpaalmd0pin4n8f620filf@4ax.com...
Spot lights and wide beam lights of the same lumens values will have a
different lighting effect. The light reflected will be more concentrated in
the narrower beam lights.
"Victor Roberts" <xxx@lighting-research.com> wrote in message
news:v3g1q0ddv5u9hpaalmd0pin4n8f620filf@4ax.com...
B
Bob Masta
Guest
On Mon, 22 Nov 2004 00:08:50 -0800, "crzndog"
<cool_blue_dog@nospam_hotmail.com> wrote:
instead of "rods". The rods are only used at very low
light levels, and are pretty much only in peripheral vision.
The 3 (or so) types of cones are used for color vision and
are packed into the fovea where you would be registering
a small spot.
Best regards,
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
<cool_blue_dog@nospam_hotmail.com> wrote:
Not to be too nit-picky here, but I think you mean "cones"
instead of "rods". The rods are only used at very low
light levels, and are pretty much only in peripheral vision.
The 3 (or so) types of cones are used for color vision and
are packed into the fovea where you would be registering
a small spot.
Best regards,
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
B
Bruce Murphy
Guest
John Cartmell <john@cartmell.demon.co.uk> writes:
B>
I've come across this claim before. Do you have a reference for it?
B>
J
John Cartmell
Guest
In article <41a1f12e.1182400@news.itd.umich.edu>,
Bob Masta <NoSpam@daqarta.com> wrote:
you get arguments about whether that dress/tie/whatever is blue or green.
Yes seriously! ;-)
--
John Cartmell john@ followed by finnybank.com FAX +44 (0)8700-519-527
Qercus magazine & FD Games www.finnybank.com www.acornuser.com
Qercus - a fusion of Acorn Publisher & Acorn User magazines
Bob Masta <NoSpam@daqarta.com> wrote:
Most people have three types. Some women have four - which is probably why
you get arguments about whether that dress/tie/whatever is blue or green.
Yes seriously! ;-)
--
John Cartmell john@ followed by finnybank.com FAX +44 (0)8700-519-527
Qercus magazine & FD Games www.finnybank.com www.acornuser.com
Qercus - a fusion of Acorn Publisher & Acorn User magazines
B
Bruce Murphy
Guest
John Cartmell <john@cartmell.demon.co.uk> writes:
B>
So 'no' then
B>
J
John Cartmell
Guest
In article <m2d5y60wi1.fsf@greybat.rattus.net>, Bruce Murphy
<pack-news@rattus.net> wrote:
so.
--
John Cartmell john@ followed by finnybank.com FAX +44 (0)8700-519-527
Qercus magazine & FD Games www.finnybank.com www.acornuser.com
Qercus - a fusion of Acorn Publisher & Acorn User magazines
<pack-news@rattus.net> wrote:
It was reported in New Scientist sometime over the last couple of months or
so.
--
John Cartmell john@ followed by finnybank.com FAX +44 (0)8700-519-527
Qercus magazine & FD Games www.finnybank.com www.acornuser.com
Qercus - a fusion of Acorn Publisher & Acorn User magazines
J
John Cartmell
Guest
In article <m28y8t29ae.fsf@greybat.rattus.net>, Bruce Murphy
<pack-news@rattus.net> wrote:
You'd accept a reference if I gave you an issue but not page. This way you
could still easily search the on-line index for NS and find the article.
--
John Cartmell john@ followed by finnybank.com FAX +44 (0)8700-519-527
Qercus magazine & FD Games www.finnybank.com www.acornuser.com
Qercus - a fusion of Acorn Publisher & Acorn User magazines
<pack-news@rattus.net> wrote:
Shan't! ;-)John Cartmell <john@cartmell.demon.co.uk> writes:
In article <m2d5y60wi1.fsf@greybat.rattus.net>, Bruce Murphy
pack-news@rattus.net> wrote:
John Cartmell <john@cartmell.demon.co.uk> writes:
In article <41a1f12e.1182400@news.itd.umich.edu>, Bob Masta
NoSpam@daqarta.com> wrote:
The 3 (or so) types of cones are used for color vision and are
packed into the fovea where you would be registering a small
spot.
Most people have three types. Some women have four - which is
probably why you get arguments about whether that
dress/tie/whatever is blue or green.
I've come across this claim before. Do you have a reference for it?
It was reported in New Scientist sometime over the last couple of
months or so.
So 'no' then
You'd accept a reference if I gave you an issue but not page. This way you
could still easily search the on-line index for NS and find the article.
--
John Cartmell john@ followed by finnybank.com FAX +44 (0)8700-519-527
Qercus magazine & FD Games www.finnybank.com www.acornuser.com
Qercus - a fusion of Acorn Publisher & Acorn User magazines
J
John Cartmell
Guest
In article <m2d5y60wi1.fsf@greybat.rattus.net>, Bruce Murphy
<pack-news@rattus.net> wrote:
imagined!
New Scientist vol 181 issue 2432 31 January 2004 page 40
Colour is detected by millions of cone cells in the retina and in a normal
person there are three types, responding to red, green and blue light. This
makes humans trichromatic and in theory allows us to distinguish between
more than 2 million different colours. Blue cones are very uniform but
there are at least four versions of the gene that encodes the red visual
pigment and four versions of the green. Because these genes are carried on
the X chromosome, and men have only one X chromosome, the variant genes are
readily expressed in men and often lead to subtle impairments in colour
vision.
But these variants don't just cause defects - they may give some women
enhanced colour vision. Because women have two X chromosomes, it is
possible for one X to carry the normal genes and the other to carry one or
other of the variants. This means some women have an extra type of cone,
making them potentially tetrachromatic. Deeb has now begun research on
these super-sighted women and says the phenomenon may not be unusual.
"Around 15 per cent of women are carriers of colour vision deficiency," he
says. "Looking at 43 of these, two showed evidence of tetrachromacy."
Samir Deep is at Columbia University, New York
--
John Cartmell john@ followed by finnybank.com FAX +44 (0)8700-519-527
Qercus magazine & FD Games www.finnybank.com www.acornuser.com
Qercus - a fusion of Acorn Publisher & Acorn User magazines
<pack-news@rattus.net> wrote:
I've been stung into double checking and time is going faster than I
imagined!
New Scientist vol 181 issue 2432 31 January 2004 page 40
Colour is detected by millions of cone cells in the retina and in a normal
person there are three types, responding to red, green and blue light. This
makes humans trichromatic and in theory allows us to distinguish between
more than 2 million different colours. Blue cones are very uniform but
there are at least four versions of the gene that encodes the red visual
pigment and four versions of the green. Because these genes are carried on
the X chromosome, and men have only one X chromosome, the variant genes are
readily expressed in men and often lead to subtle impairments in colour
vision.
But these variants don't just cause defects - they may give some women
enhanced colour vision. Because women have two X chromosomes, it is
possible for one X to carry the normal genes and the other to carry one or
other of the variants. This means some women have an extra type of cone,
making them potentially tetrachromatic. Deeb has now begun research on
these super-sighted women and says the phenomenon may not be unusual.
"Around 15 per cent of women are carriers of colour vision deficiency," he
says. "Looking at 43 of these, two showed evidence of tetrachromacy."
Samir Deep is at Columbia University, New York
--
John Cartmell john@ followed by finnybank.com FAX +44 (0)8700-519-527
Qercus magazine & FD Games www.finnybank.com www.acornuser.com
Qercus - a fusion of Acorn Publisher & Acorn User magazines
T
Tony Morgan
Guest
On Mon, 22 Nov 2004 15:58:25 +0000 (GMT), John Cartmell
<john@cartmell.demon.co.uk> wrote:
a search at: http://archive.newscientist.com/ and there's nothing
there.
Tomorrow, just to be sure, i'll dig out old copies of NS from my loft.
It's so easy to claim attributes, but when it's so easily disconunted
it seems foolish to do so (not that I disbelieve you).
<john@cartmell.demon.co.uk> wrote:
I subscribe to NS and I don't recall anything on the subject. So I didIn article <m28y8t29ae.fsf@greybat.rattus.net>, Bruce Murphy
pack-news@rattus.net> wrote:
John Cartmell <john@cartmell.demon.co.uk> writes:
In article <m2d5y60wi1.fsf@greybat.rattus.net>, Bruce Murphy
pack-news@rattus.net> wrote:
John Cartmell <john@cartmell.demon.co.uk> writes:
In article <41a1f12e.1182400@news.itd.umich.edu>, Bob Masta
NoSpam@daqarta.com> wrote:
The 3 (or so) types of cones are used for color vision and are
packed into the fovea where you would be registering a small
spot.
Most people have three types. Some women have four - which is
probably why you get arguments about whether that
dress/tie/whatever is blue or green.
I've come across this claim before. Do you have a reference for it?
It was reported in New Scientist sometime over the last couple of
months or so.
So 'no' then
Shan't! ;-)
You'd accept a reference if I gave you an issue but not page. This way you
could still easily search the on-line index for NS and find the article.
a search at: http://archive.newscientist.com/ and there's nothing
there.
Tomorrow, just to be sure, i'll dig out old copies of NS from my loft.
It's so easy to claim attributes, but when it's so easily disconunted
it seems foolish to do so (not that I disbelieve you).
B
Bruce Murphy
Guest
John Cartmell <john@cartmell.demon.co.uk> writes:
Now I'm going to tootle down to the library and see whether I can find
any references for it.
In my defence my 'so "no" then' was more to do with New Scientists
breathlessness before accuracy editorial policy than anything else.
B>
thank you
Now I'm going to tootle down to the library and see whether I can find
any references for it.
In my defence my 'so "no" then' was more to do with New Scientists
breathlessness before accuracy editorial policy than anything else.
B>
J
Jukka Aho
Guest
Bruce Murphy wrote:
story about scientists looking for (or testing and studying) possible
tetrachromats - which, as suggested by genetic research, should all
be women - was published in several magazines some 4 or 5 years ago.
I read the original article (by Glenn Zorbette) from Red Herring, but
it has been reprinted elsewhere, for example:
<http://www.freerepublic.com/forum/a3a24199b1ef8.htm>
<http://www.cs.utk.edu/~evers/documents/tetraChromat.txt>
--
znark
Google for "Looking for Madam Tetrachromat" and "tetrachromacy". The
story about scientists looking for (or testing and studying) possible
tetrachromats - which, as suggested by genetic research, should all
be women - was published in several magazines some 4 or 5 years ago.
I read the original article (by Glenn Zorbette) from Red Herring, but
it has been reprinted elsewhere, for example:
<http://www.freerepublic.com/forum/a3a24199b1ef8.htm>
<http://www.cs.utk.edu/~evers/documents/tetraChromat.txt>
--
znark
B
Bruce Murphy
Guest
"Jukka Aho" <jukka.aho@iki.fi> writes:
http://www.rmki.kfki.hu/~lukacs/TETRACH.htm
B>
I found the following article somewhat more detailed and interesting.
http://www.rmki.kfki.hu/~lukacs/TETRACH.htm
B>
B
Bob Masta
Guest
On Mon, 22 Nov 2004 14:27:36 +0000 (GMT), John Cartmell
<john@cartmell.demon.co.uk> wrote:
There is an additional phenomenon recently described/proposed
by my old friend Angela Brown. Seems the blue cones are easily
damaged by UV exposure, which gives old vision a brownish tint
(called "brunescence"). She and her co-author noted that in
equatorial countries (lots of UV exposure) there tends to be be
little or no distinction between shades of blue... most of the
languages in those countries tend to call all bluish colors by
the same general name, which translates to something like
"dark" in each language. Tests on subjects show that they
do indeed have significant brunescence by early adulthood,
comparable to 90-year-old outdoor workers in northern
regions. She has a demo of what the differences look
like with and without this brunescence, and it's pretty
dramatic. Unfortunately, it's not available on the Web
anywhere... you have to attend one of her talks
to see it, at the moment.
Best regards,
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
<john@cartmell.demon.co.uk> wrote:
Not to mention all the dichromats (color-blind) viewers of the world.
There is an additional phenomenon recently described/proposed
by my old friend Angela Brown. Seems the blue cones are easily
damaged by UV exposure, which gives old vision a brownish tint
(called "brunescence"). She and her co-author noted that in
equatorial countries (lots of UV exposure) there tends to be be
little or no distinction between shades of blue... most of the
languages in those countries tend to call all bluish colors by
the same general name, which translates to something like
"dark" in each language. Tests on subjects show that they
do indeed have significant brunescence by early adulthood,
comparable to 90-year-old outdoor workers in northern
regions. She has a demo of what the differences look
like with and without this brunescence, and it's pretty
dramatic. Unfortunately, it's not available on the Web
anywhere... you have to attend one of her talks
to see it, at the moment.
Best regards,
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
D
Don Klipstein
Guest
In article <5lf1q0pltuo3kol8mti2np0us5rt8ovq2t@4ax.com>, Victor Roberts wrote:
lumen output mentioned in:
http://www.nichia.co.jp/product/led-smd-powerled.html
That web page mentions 42 lumens as some sort of typical, and the
minimum for brightness rank Jc is 36.
This is at case temperature of 25 C, as opposed to Lumileds specifying a
junction temperature of 25 C, according to Nichia's datasheet.
Voltage drop is typically 3.6 volts, max. for the upper-middle voltage
rank drop is 4.0 volts, and max for the highest rank (worst) voltage drop
is 4.3 volts.
36 lumens at 4.3 volts at .35 amp works out to... 23.9 lumens/watt
This is a real worst case assuming you get the brightness rank that
includes the lumen figure mentioned in the above-mentioned web page.
"Typical" (maybe a bit optimistic for now) is 42 lumens at 3.6 volts at
..35 amp, which works out to 33 lumens/watt.
I would be a bit concerned about these figures being a bit optimistic
because most of the major manufacturers appear to have been one-upping
each other in their claims recently now that Cree is in the 350 mA white
LED game.
However, Cree has been advancing somewhat steadily at least their
claimed blue LED chip performance over the years, so I expect white
LED output to advance enough for the current claims to soon enough be
conservative rather than optimistic. Optimistic would then be the next
round of even higher claims for output and overall luminous efficacy.
(Cree has a 350 mA white LED with output minimum 40 typical 45 lumens
supposedly hitting production next month. I believe, based on the
datasheet for the "dice" (chips) that I believe they use, that the
voltage drop is typically 3.4, maximum 3.9 volts. This works out
to luminous efficacy of minimum 29.3 "typically" 37.5 lumens/watt. This
is one of their "XL7090" LED "lamps".
Cree specifies ambient temperature of 25 degrees C for their current
XL7090 products in http://www.cree.com/Products/lmp_7090.asp
-?? specify ambient temperature rather than case temperature for a product
that requires a heatsink??)
lumens/watt if the worst case voltage drop decreases with increasing
temperature the same as typical voltage drop does. With a thermal
resistance of 17 degrees C per watt and 3.06 watts, junction temp. is 77
degrees C. Looks like you get 82% of the light output that you get with
the junction temperature at 25 degrees C.
The Luxeon III "emitter" has a thermal resistance of 13 degrees C per
watt as opposed to 17 for the "star", making the worst case junction
temperature slightly over 12 degrees C cooler, increasing light output
slightly over 4% (and voltage drop .5-.6%) higher - let's say worst case
overall luminous efficacy is 3.5% better than that of the "star", or 16.6
lumens/watt. Of course this assumes cooling the smaller heatsink surface
of the "emitter" to 25 degrees C.
I do not like the way Lumileds has their nominal performance specified
at a junction temperature that requires a heatsink temperature of
typically -19 degrees C (-2 degrees F) (for Luxeon III "star") if operated
continuously.
- Don Klipstein (don@misty.com)
Nichia NCCW022, of brightness rank Jc - the rank that includes the 42
lumen output mentioned in:
http://www.nichia.co.jp/product/led-smd-powerled.html
That web page mentions 42 lumens as some sort of typical, and the
minimum for brightness rank Jc is 36.
This is at case temperature of 25 C, as opposed to Lumileds specifying a
junction temperature of 25 C, according to Nichia's datasheet.
Voltage drop is typically 3.6 volts, max. for the upper-middle voltage
rank drop is 4.0 volts, and max for the highest rank (worst) voltage drop
is 4.3 volts.
36 lumens at 4.3 volts at .35 amp works out to... 23.9 lumens/watt
This is a real worst case assuming you get the brightness rank that
includes the lumen figure mentioned in the above-mentioned web page.
"Typical" (maybe a bit optimistic for now) is 42 lumens at 3.6 volts at
..35 amp, which works out to 33 lumens/watt.
I would be a bit concerned about these figures being a bit optimistic
because most of the major manufacturers appear to have been one-upping
each other in their claims recently now that Cree is in the 350 mA white
LED game.
However, Cree has been advancing somewhat steadily at least their
claimed blue LED chip performance over the years, so I expect white
LED output to advance enough for the current claims to soon enough be
conservative rather than optimistic. Optimistic would then be the next
round of even higher claims for output and overall luminous efficacy.
(Cree has a 350 mA white LED with output minimum 40 typical 45 lumens
supposedly hitting production next month. I believe, based on the
datasheet for the "dice" (chips) that I believe they use, that the
voltage drop is typically 3.4, maximum 3.9 volts. This works out
to luminous efficacy of minimum 29.3 "typically" 37.5 lumens/watt. This
is one of their "XL7090" LED "lamps".
Cree specifies ambient temperature of 25 degrees C for their current
XL7090 products in http://www.cree.com/Products/lmp_7090.asp
-?? specify ambient temperature rather than case temperature for a product
that requires a heatsink??)
Close to what I got for Luxeon III "star"... I figure about 16.1
lumens/watt if the worst case voltage drop decreases with increasing
temperature the same as typical voltage drop does. With a thermal
resistance of 17 degrees C per watt and 3.06 watts, junction temp. is 77
degrees C. Looks like you get 82% of the light output that you get with
the junction temperature at 25 degrees C.
The Luxeon III "emitter" has a thermal resistance of 13 degrees C per
watt as opposed to 17 for the "star", making the worst case junction
temperature slightly over 12 degrees C cooler, increasing light output
slightly over 4% (and voltage drop .5-.6%) higher - let's say worst case
overall luminous efficacy is 3.5% better than that of the "star", or 16.6
lumens/watt. Of course this assumes cooling the smaller heatsink surface
of the "emitter" to 25 degrees C.
I do not like the way Lumileds has their nominal performance specified
at a junction temperature that requires a heatsink temperature of
typically -19 degrees C (-2 degrees F) (for Luxeon III "star") if operated
continuously.
- Don Klipstein (don@misty.com)
B
Bob Masta
Guest
On Tue, 23 Nov 2004 13:55:02 GMT, NoSpam@daqarta.com (Bob Masta)
wrote:
<snip>
blue cones, but rather to damage to the lens. (I'd guess
that might even protect the blue cones, by restricting the
light reaching them.)
"Senescence" is due to damage to little grey cells that
make me forget these critical details!
caused!
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
wrote:
<snip>
CORRECTION: Brunescence is not due to damage to the
blue cones, but rather to damage to the lens. (I'd guess
that might even protect the blue cones, by restricting the
light reaching them.)
"Senescence" is due to damage to little grey cells that
make me forget these critical details!
Sorry for any confusion my senescence may have
caused!
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
V
Victor Roberts
Guest
On Wed, 24 Nov 2004 04:40:45 +0000 (UTC), don@manx.misty.com (Don
Klipstein) wrote:
find in an order of these devices. Nichia states on their data sheet
for this LED: "One delivery will include up to two color ranks, four
luminous flux ranks and three forward voltage ranks of the product.
THE QUANTITY-RATIO OF THE RANKS IS DECIDED BY NICHIA." [Emphasis is
mine.]
So, the customer has no control at all over what rank LEDs he or she
gets from Nichia and cannot design a product or application around the
so-called minimum output of the Rank Jc device. They must assume that
some, or perhaps all, of the devices they receive will be Rank Ja,
which has only one half the performance of the Rank Jc devices.
assumption that any order would include some or all Rank Ja devices.
that the specifying ambient temperature is a bit confusing for a
device that needs an additional heat sink.
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.
Klipstein) wrote:
Good find, but this is not a the real minimum that a customer would
find in an order of these devices. Nichia states on their data sheet
for this LED: "One delivery will include up to two color ranks, four
luminous flux ranks and three forward voltage ranks of the product.
THE QUANTITY-RATIO OF THE RANKS IS DECIDED BY NICHIA." [Emphasis is
mine.]
So, the customer has no control at all over what rank LEDs he or she
gets from Nichia and cannot design a product or application around the
so-called minimum output of the Rank Jc device. They must assume that
some, or perhaps all, of the devices they receive will be Rank Ja,
which has only one half the performance of the Rank Jc devices.
No, the real worst case is about half your number, based on the
assumption that any order would include some or all Rank Ja devices.
I find only typical output data given at the link you provide. I agree
that the specifying ambient temperature is a bit confusing for a
device that needs an additional heat sink.
--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.
D
Don Klipstein
Guest
In <g269q0lgua82t4olk9kro7omo656ittf1u@4ax.com>, Victor Roberts wrote
in part:
press release:
http://www.cree.com/News/news210.asp
- Don Klipstein (don@misty.com)
in part:
Sorry, the 40 lumen minimum for the soon-to-come part is in this Cree
press release:
http://www.cree.com/News/news210.asp
- Don Klipstein (don@misty.com)
V
Victor Roberts
Guest
On Wed, 24 Nov 2004 14:49:09 +0000 (UTC), don@manx.misty.com (Don
Klipstein) wrote:
--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.
Klipstein) wrote:
Thanks Don.
--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.