Just had one of those weekly e-ads from a local department store that we use
sometimes, trumpeting the latest "Ultraslim LED TV" from Samsung.

Ha! I thought. I haven't heard anything about this. Is it OLED ? At sizes up
to over 50", that didn't seem likely, so I followed the links to see what it
was all about.

Seems that these sets still actually have an LCD display panel, but the
*backlighting* is LED ...

OK, so I can see that there are advantages size-wise - these things are
only 32mm thick - and also power consumption savings, as we all know that
flourescent tube backlighting is very inefficient, but is it right to
actually call these "LED TVs" ? Seems like a bit of a deliberately
misleading use of the terminology to me - or is it maybe just me being a
picky grumpy old sod ? d:~)

Arfa

Arfa Daily coughed up some electrons that declared:

Just had one of those weekly e-ads from a local department store that we
use sometimes, trumpeting the latest "Ultraslim LED TV" from Samsung.

Ha! I thought. I haven't heard anything about this. Is it OLED ? At sizes
up to over 50", that didn't seem likely, so I followed the links to see
what it was all about.

Seems that these sets still actually have an LCD display panel, but the
*backlighting* is LED ...

OK, so I can see that there are advantages size-wise - these things are
only 32mm thick - and also power consumption savings, as we all know that
flourescent tube backlighting is very inefficient, but is it right to
actually call these "LED TVs" ? Seems like a bit of a deliberately
misleading use of the terminology to me - or is it maybe just me being a
picky grumpy old sod ? d:~)

Arfa

This by any chance?

http://www.ebuyer.com/product/162377

Drop a line to Trading Standards for mis-description.

I agree - "LED TV means the primary display is LED, not LED backlit LCD".
There's a world of difference and calling an LCD and LED is clearly
designed to misrepresent the product as something it's not.

I'll have an LED TV when they become cheap/big enough

Cheers

Tim

Arfa Daily coughed up some electrons that declared:

Just had one of those weekly e-ads from a local department store that we
use sometimes, trumpeting the latest "Ultraslim LED TV" from Samsung.

Ha! I thought. I haven't heard anything about this. Is it OLED ? At sizes
up to over 50", that didn't seem likely, so I followed the links to see
what it was all about.

Seems that these sets still actually have an LCD display panel, but the
*backlighting* is LED ...

OK, so I can see that there are advantages size-wise - these things are
only 32mm thick - and also power consumption savings, as we all know that
flourescent tube backlighting is very inefficient, but is it right to
actually call these "LED TVs" ? Seems like a bit of a deliberately
misleading use of the terminology to me - or is it maybe just me being a
picky grumpy old sod ? d:~)

Arfa

This is more descriptive, though the tile seems misleading:

http://www.comet.co.uk/shopcomet/adv...amsung-7series

The bit about turning backlights on and off selectively to enhance blacks is
fair enough - a genuine advancement. But it's still not an LED TV, it's and
LED enhanced (or "intelligent LED backlight") LCD TV.

Here's what Samsung say:

http://www.samsung.com/uk/consumer/d... tents_series7

They seem to be rather overplaying the LED card, mentioning "single seamless
crystal" (I thought LCD meant Liquid Crystal)

And here's what TheRegister says:

http://www.reghardware.co.uk/2009/01...sung_le40a786/

That seems to get to the point. The LED arrays are not pixel resolution.

All rather fuzzy...

They should just be honest and say "Smart LED lit ultra thin LCD" - I'd
still be impressed.

In article ,
Arfa Daily wrote:
Just had one of those weekly e-ads from a local department store that we
use sometimes, trumpeting the latest "Ultraslim LED TV" from Samsung.

Ha! I thought. I haven't heard anything about this. Is it OLED ? At
sizes up to over 50", that didn't seem likely, so I followed the links
to see what it was all about.

Seems that these sets still actually have an LCD display panel, but the
*backlighting* is LED ...

Yup. There are what can be accurately described as LED TVs on the horizon
- OLED. But are some way off in normal sizes at an affordable cost.

OK, so I can see that there are advantages size-wise - these things
are only 32mm thick - and also power consumption savings, as we all know
that flourescent tube backlighting is very inefficient, but is it right
to actually call these "LED TVs"

Who says fluorescent is inefficient? LED could be better if you could turn
off those in the dark parts of the picture - but no claims for that. Other
problem with LEDs is producing a continuous spectrum smooth white light -
needed to give all the colours from LCD.

? Seems like a bit of a deliberately misleading use of the terminology
to me - or is it maybe just me being a picky grumpy old sod ? d:~)

Might as well claim any TV is LED - if it has an LED warning light. ;-)

--
*Who is this General Failure chap anyway - and why is he reading my HD? *

Dave Plowman London SW
To e-mail, change noise into sound.

On Mon, 11 May 2009 13:28:06 +0100 "Dave Plowman (News)"
wrote in Message id:
:

Yup. There are what can be accurately described as LED TVs on the horizon
- OLED. But are some way off in normal sizes at an affordable cost.

I took a look at Sony's offering. IIRC it's about 11" diagonally and about
$2500! I downloaded an operators manual, and noticed there were warnings
about screen burn when a steady single image is displayed. Think I'll
stick with my $800 42" LCD.

I've seen this set at Fry's. It has problems.

The demo apparently was set in "store" mode, with a rather over-bright,
harsh-looking picture.

This set also has frame interpolation (to reduce smear in fast-moving
images), but the unintended result (which I've seen on other sets with
interpolation) is to make films look like video. I don't like it.

This is a fairly expensive set (for its size). I would not recommend it.

"Dave Plowman (News)" wrote in message
...
In article ,
Arfa Daily wrote:
Just had one of those weekly e-ads from a local department store that we
use sometimes, trumpeting the latest "Ultraslim LED TV" from Samsung.

Ha! I thought. I haven't heard anything about this. Is it OLED ? At
sizes up to over 50", that didn't seem likely, so I followed the links
to see what it was all about.

Seems that these sets still actually have an LCD display panel, but the
*backlighting* is LED ...

Yup. There are what can be accurately described as LED TVs on the horizon
- OLED. But are some way off in normal sizes at an affordable cost.

OK, so I can see that there are advantages size-wise - these things
are only 32mm thick - and also power consumption savings, as we all know
that flourescent tube backlighting is very inefficient, but is it right
to actually call these "LED TVs"

Who says fluorescent is inefficient? LED could be better if you could turn
off those in the dark parts of the picture - but no claims for that. Other
problem with LEDs is producing a continuous spectrum smooth white light -
needed to give all the colours from LCD.

? Seems like a bit of a deliberately misleading use of the terminology
to me - or is it maybe just me being a picky grumpy old sod ? d:~)

Might as well claim any TV is LED - if it has an LED warning light. ;-)

--
*Who is this General Failure chap anyway - and why is he reading my HD? *

Dave Plowman London SW
To e-mail, change noise into sound.


I'm not disputing - not that anyone is suggesting that I am of course -
that this is very possibly a distinct improvement over the existing
backlight technology. I haven't actually seen one 'in the flesh' yet, but I
will look out for one next time I am in JL or Waitrose. I am expecting, as
it is from Sammy, that it will probably be very good. But following up on
Tim's link to "what Samsung say ..." I am very surprised that as a reputable
company, they have made such a deliberate attempt to 'fuzz the edges' on
this, and go out of their way to suggest that it is something other than an
LCD screen.

And as to who says that flourescent backlighting is inefficient - well I do,
actually. I have this morning been mending a bunch of LCD TV power supplies
that I do regularly for a company. They come from a manufacturer that
supplies them to many TV manufacturers for use in their LCD TV sets. The
main - as in biggest, chunkiest and most heatsunk - rail, is without doubt
the 24v one that feeds mostly the backlights. A small amount of power is
also drawn from this rail by the audio output stages, but by far the lion's
share goes to the backlight inverter.

This rail is designed to supply up to 5 amps, and an average sized LCD TV -
say a 28 or 32" - pulls around 4 amps off it to run the backlights. That's
100 watts. An awful lot of power to produce the amount of light that the
tubes do. A considerable amount of that input power goes to losses in the
inverter board, which runs pretty hot, and also to losses in the tubes,
which can get hot enough to be uncomfortable to touch. The LCD TV that I
have on my kitchen wall produces enough heat from the backlights, that you
can feel it on your face, rolling off the front of the screen as you walk
past.

If the LED backlighting that Sammy are using, is as bright or brighter than
the flourescent equivalent, I would be very surprised if it was consuming
more than 20 watts, even with the whole array on.

Arfa

Who says fluorescent is inefficient? LED could be better if you could
turn off those in the dark parts of the picture -- but no claims for that.

Quite the contrary. Many LED sets use local dimming to improve image
contrast.


Other problem with LEDs is producing a continuous spectrum smooth
white light -- needed to give all the colours from LCD.

The last thing you want is a continuous spectrum.

On May 11, 1:52*pm, JW wrote:
On Mon, 11 May 2009 13:28:06 +0100 "Dave Plowman (News)"
wrote in Message id:
:

Yup. There are what can be accurately described as LED TVs on the horizon
- OLED. But are some way off in normal sizes at an affordable cost.

I took a look at Sony's offering. IIRC it's about 11" diagonally and about
$2500! I downloaded an operators manual, and noticed there were warnings
about screen burn when a steady single image is displayed. Think I'll
stick with my $800 42" LCD.

It was crap in all respects and ended up being sold off in bargain
basement stores.

MBQ

On Mon, 11 May 2009 12:12:08 +0100, "Arfa Daily"
wrote:

...but is it right to
actually call these "LED TVs" ? Seems like a bit of a deliberately
misleading use of the terminology to me - or is it maybe just me being a
picky grumpy old sod ? d:~)

Sure. You've just been LED astray.
(Sorry, I couldn't resist).

I notice that Samsung's web pile conveniently does NOT mention
anything about the technology used in their Luxia line of TV's.
They've even dropped the Luxia name, preferring to use "LED TV"
instead. My suspicious mind suggests that this seems intentional.
http://www.samsung.com/us/productsubtype/led/

Perhaps it would be helpful to refer to Samsung TV's by their
backlighting. The ordinary LCD panel TV can be known as "CCFL TV".

As for improved efficiency, I'm wondering if that's true. CCFL lamps
belch about 80-100 lumens/watt. Typical white LED's do 10-20
lumens/watt.
http://en.wikipedia.org/wiki/Light-emitting_diode#Efficiency_and_operational_paramete rs
http://en.wikipedia.org/wiki/Fluorescent_lamp#Luminous_efficacy
To get the same light output, LED's need to about 4-5 times as much
power. If Samsung used the new and recently demonstrated high
efficiency white LED's, at 100 lumens/watt efficiency, they would at
best be equal to the efficiency of CCFL. Unless my arithmetic is
faulty, an common white LED backlit TV would belch MORE heat than a
CCFL backlit TV for the same brightness. In addition, the smaller
physical size (thickness) of the LED backlit TV leaves less area for
ventilation and conductive cooling. Looking back at the
"specifications" pages, on the Samsung web pile, I don't seem to find
a power consumption figure. Oh-oh....





--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

As for improved efficiency, I'm wondering if that's true. CCFL lamps
belch about 80-100 lumens/watt. Typical white LED's do 10-20
lumens/watt.

I believe Sony uses RGB LEDs. The R and G should be more efficient.

In article ,
Arfa Daily wrote:
And as to who says that flourescent backlighting is inefficient - well I
do, actually. I have this morning been mending a bunch of LCD TV power
supplies that I do regularly for a company. They come from a
manufacturer that supplies them to many TV manufacturers for use in
their LCD TV sets. The main - as in biggest, chunkiest and most
heatsunk - rail, is without doubt the 24v one that feeds mostly the
backlights. A small amount of power is also drawn from this rail by the
audio output stages, but by far the lion's share goes to the backlight
inverter.

And the same will apply to LED backlights. It's a big con that LED are
more efficient - they only are where supplying narrow bandwidth light. As
soon as you try and make them produce continuous spectrum light - ie white
- the efficiency goes way down. Of course they may improve - but then
again so may fluorescent.

--
*Women like silent men; they think they're listening.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
William Sommerwerck wrote:
Who says fluorescent is inefficient? LED could be better if you could
turn off those in the dark parts of the picture -- but no claims for
that.

Quite the contrary. Many LED sets use local dimming to improve image
contrast.

No claims for that I could see. If it does can only be a good thing as it
could give truer blacks as well - a problem with any backlit device.


Other problem with LEDs is producing a continuous spectrum smooth
white light -- needed to give all the colours from LCD.

The last thing you want is a continuous spectrum.

Eh?

--
*How do they get the deer to cross at that yellow road sign?

Dave Plowman London SW
To e-mail, change noise into sound.

And the same will apply to LED backlights. It's a big con that
LEDs are more efficient -- they only are where supplying narrow-
bandwidth light. As soon as you try and make them produce
continuous-spectrum light -- ie white -- the efficiency goes way
down. Of course, they may improve -- but then again, so may
fluorescent.

White LEDs are not continuous-spectrum. They contain a phosphor that
produces yellow light when stimulated by blue light.

In article ,
William Sommerwerck wrote:
And the same will apply to LED backlights. It's a big con that
LEDs are more efficient -- they only are where supplying narrow-
bandwidth light. As soon as you try and make them produce
continuous-spectrum light -- ie white -- the efficiency goes way
down. Of course, they may improve -- but then again, so may
fluorescent.

White LEDs are not continuous-spectrum. They contain a phosphor that
produces yellow light when stimulated by blue light.

Indeed. So not suitable for where you need a decent quality light. As for
an LCD backlight.

--
*Save a tree, eat a beaver*

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Dave Plowman (News) wrote:

Who says fluorescent is inefficient? LED could be better if you could turn
off those in the dark parts of the picture - but no claims for that.

A video engineer I know, recently told me that some of the new
LED-backed-LCD displays do just that.

If I understand him correctly: these displays use a large matrix of
addressable R/G/B LEDs, with each LED illuminating the back size of a
set of LCD pixels. The actual visual brightness seen by the viewer,
for each individual pixel, depends both on the level of LED
back-illumination for that pixel, and the transparency of the LCD
pixel... both of which can be controlled by the display electronics.

By turning down (or off) the LED which back-illuminates a set of
pixels, the display can generate a *very* "deep black" in that area
when called for... these displays have a much higher maximum contrast
ratio than a traditional CFL-backlit LCD display.

This approach can save power, too, during times of low average screen
brightness.

These aren't OLED displays (which are still expensive for their
size)... the LEDs are of fairly standard inorganic construction.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In article ,
Dave Plowman (News) wrote:

And the same will apply to LED backlights. It's a big con that LED are
more efficient - they only are where supplying narrow bandwidth light. As
soon as you try and make them produce continuous spectrum light - ie white
- the efficiency goes way down. Of course they may improve - but then
again so may fluorescent.

You're assuming that the designers use LEDs to create
continuous-spectrum light, and then pixel-filter this down to the
R/G/B pixels.

My understanding is that this is *not* what they're doing. Rather,
I'm told that they use a matrix of individual narrow-emission R/G/B
LEDs, which backlight the R/G/B-filtered LCD pixel "shutters".

With proper selection of the R/G/B LED wavelengths (e.g. pick them
with peak output wavelengths close to the peak-optical-sensitivity
wavelengths of the photopigments in the human retina) you ought to be
able to get very good efficiency.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"William Sommerwerck" wrote in message
...
Who says fluorescent is inefficient? LED could be better if you could
turn off those in the dark parts of the picture -- but no claims for
that.

Quite the contrary. Many LED sets use local dimming to improve image
contrast.


Other problem with LEDs is producing a continuous spectrum smooth
white light -- needed to give all the colours from LCD.

The last thing you want is a continuous spectrum.




Local is a relative term and the effectiveness of these systems varies
considerably with real video. On/off contrast ratios can be impressive, but
the real test is how it performs with live video.

As for "continuous" spectra, again, it depends. Ideally, for a standard
video matrix decoding typical video, you would want spectra for R, G, & B
that match the CIE standard observer functions. These are what cameras are
designed to output, and what CRTs were more likely to approximate. You have
to account for narrow spectrum in the outputs of displays in the matrix for
the color decoder. Some sets have done a better job of this than others.

Like most technologies, there are caveats and implementation variance that
make some work very well and others less so. The best sets from Samsung and
the Sony look great, but still not as good in terms of blacks on real video
as the best PDPs. The color on the Sony seems more natural than that of the
Samsung to me, but neither are up to the best CRTs nor PDPs, yet. Darned
close, and better than many of the lesser from either technology. Any of
them properly calibrated will likely outperform any of the others out of the
box.

Leonard

In article ,
"Dave Plowman (News)" writes:
In article ,
William Sommerwerck wrote:
And the same will apply to LED backlights. It's a big con that
LEDs are more efficient -- they only are where supplying narrow-
bandwidth light. As soon as you try and make them produce
continuous-spectrum light -- ie white -- the efficiency goes way
down. Of course, they may improve -- but then again, so may
fluorescent.

White LEDs are not continuous-spectrum. They contain a phosphor that
produces yellow light when stimulated by blue light.

Indeed. So not suitable for where you need a decent quality light. As for
an LCD backlight.

I don't see why an LCD backlight needs to be anything other than
red green and blue, and having just checked one, that's exactly
what it is -- actually very much narrower bands than a regular
fluorescent, and without any of the other fill-in colours you
get from a fluorescent lamp. After all, anything else from the
backlight would be wasted (or worse, might bleed through into
some colour cells and contaminate the primary additive colours).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"Andrew Gabriel" andrew@a20 wrote in message
...
In article ,
"Dave Plowman (News)" writes:
In article ,
William Sommerwerck wrote:
And the same will apply to LED backlights. It's a big con that
LEDs are more efficient -- they only are where supplying narrow-
bandwidth light. As soon as you try and make them produce
continuous-spectrum light -- ie white -- the efficiency goes way
down. Of course, they may improve -- but then again, so may
fluorescent.

White LEDs are not continuous-spectrum. They contain a phosphor that
produces yellow light when stimulated by blue light.

Indeed. So not suitable for where you need a decent quality light. As for
an LCD backlight.

I don't see why an LCD backlight needs to be anything other than
red green and blue, and having just checked one, that's exactly
what it is -- actually very much narrower bands than a regular
fluorescent, and without any of the other fill-in colours you
get from a fluorescent lamp. After all, anything else from the
backlight would be wasted (or worse, might bleed through into
some colour cells and contaminate the primary additive colours).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
Y
That depends on the assumptions you make in the production of the source and
the decoding to those narrow spectrum RGB displays. You may or may not end
up with the same distribution of secondary and intermediate colors. The
human eye perceives color over a spectrum approximated by the CIE standard
observer curves. Concentrating all of the energy at narrow bands can have
some very significant effects, not only in overall brightness, but in color
reproduction. While it is true that any color (within a given gamut) can be
made up of a combination of narrow band RGB display sources, getting the
right spectral power at a given color requires mapping from what the pickup
and encoding assume to what the display can produce. Unfortunately, there
are not many good options for measuring response at colors other than
primaries and secondaries and no good standards for evaluating performance
objectively at this time for intermediate colors, much less for those colors
over a range of luminance values.

Leonard

In article ,
Dave Plowman (News) wrote:

LED could be better if you could turn off those in the dark parts of
the picture - but no claims for that.



Philps has a TV that does this...

http://www.reghardware.co.uk/2008/08...led_backlight/

Dunno how well it works but they claim huge improvements in contrast.

Darren

On Mon, 11 May 2009 15:28:32 -0400, Leonard Caillouet wrote:

snip lots of technical stuff

You are quite right, but if VHS taught us anything, surely it's that 'it
looks OK to me' is the usual quality assessment.

At which point the huge power reduction of LED backlights is a big plus.

We're not all trying to get Pantone matched TVs and watch them in a
darkened room, to get the colours just so.

It does not require a continuous spectrum of light, however it must
have certain wavelengths. It may require a trip to a textbook to
understand it fully, but I will make an attempt.

In a TV, even if it is an LCD, they are using an additive color
mixture. You basically need certain wavelengths of each primary color.
This differs from subtractive colorimetry which is used for example in
printers. In other words you can't make pure red out of orange and
purple. The problem might be well described as color pollution, not
much unlike impurities in a regular CRT.

Now whether we are talking about a phosphor or a color filter matters
not. The color must be pure otherwise the -Y component will have to be
accentualted for good color reproduction, and you never get it. Even
notice on some CRT sets that some of them are better at reproducing
very deep blue. Those are the RPTV CRT set in which you must defocus
the blue because that phosphor is quite inefficient. With the blue in
prefect focus you will not get the right color temperature without
overdriving the blue no matter how new the set is. Other manufacturers
intentionally pollute the blue to bring color temperature up to the
proper level. They have the advanage of being able to display a
sharp blue only part of a scene, but it simply is not AS blue.

Another example would be the low end NAPs of the past, the reds were
orange and while they looked better under bright flourescent lights,
once you got them home, in time you would fall in hate with them. And
there is no fixing this in the color circuitry.

Now I am fully aware that there have been seven color printers, but
such enhancements are simply not practical for display technology.
That's the rules of the game, I didn't make them. Actually I haven't
seen a seven color printer for quite some time, they may have
abandoned the technique. I suspect it may just be too expensive, and
think of what something like that would do to the cost of a TV set or
monitor.

However, I suspect there is some actual white enhancement going on in
some LCD units, and as many are aware, the color wheel in a DLP
frequently has more than the three primary colors. I say this because
after observing the display on one of those Zeniths which had a bad
(and removed) blue polarizing filter, it could still reproduce white.
Problem is it could only do it in the OSD. There was absolutely no
modulation of the blue in the active video. So where did the white
come from ?

Red green and blue are defined scientifically as primary colors. I
don't know where those standards came from, nor do I care, but they
are there. There is an inversion in the equation when you go from
supplying the light to using incident light. A printer makes red by
mixing yellow and magenta, but in this, it simply doesn't work. In the
subtractive mode, by the same token, the yellow, magenta and cyan have
to be pretty close to the defined complimentary colors or rendition
will suffer.

However there is still the subjective aspect. Some people would find
more pleasing to watch a DLP, and swear that the picture looks better,
and that could be attributed to it using more than three colors. If so
are they watching a more accurate picture, or is it something they
simply prefer, like speakers with alot of bass or something like
that ?

JURB

In article ,
"Leonard Caillouet" writes:
"Andrew Gabriel" andrew@a20 wrote in message
...
In article ,
"Dave Plowman (News)" writes:
In article ,
William Sommerwerck wrote:
And the same will apply to LED backlights. It's a big con that
LEDs are more efficient -- they only are where supplying narrow-
bandwidth light. As soon as you try and make them produce
continuous-spectrum light -- ie white -- the efficiency goes way
down. Of course, they may improve -- but then again, so may
fluorescent.

White LEDs are not continuous-spectrum. They contain a phosphor that
produces yellow light when stimulated by blue light.

Indeed. So not suitable for where you need a decent quality light. As for
an LCD backlight.

I don't see why an LCD backlight needs to be anything other than
red green and blue, and having just checked one, that's exactly
what it is -- actually very much narrower bands than a regular
fluorescent, and without any of the other fill-in colours you
get from a fluorescent lamp. After all, anything else from the
backlight would be wasted (or worse, might bleed through into
some colour cells and contaminate the primary additive colours).

Y
That depends on the assumptions you make in the production of the source and
the decoding to those narrow spectrum RGB displays. You may or may not end
up with the same distribution of secondary and intermediate colors. The
human eye perceives color over a spectrum approximated by the CIE standard
observer curves. Concentrating all of the energy at narrow bands can have
some very significant effects, not only in overall brightness, but in color
reproduction. While it is true that any color (within a given gamut) can be
made up of a combination of narrow band RGB display sources, getting the
right spectral power at a given color requires mapping from what the pickup
and encoding assume to what the display can produce. Unfortunately, there
are not many good options for measuring response at colors other than
primaries and secondaries and no good standards for evaluating performance
objectively at this time for intermediate colors, much less for those colors
over a range of luminance values.

I agree, but the data is already split into RGB components before it
gets to the monitor. The monitor can't make up the colours inbetween;
it doesn't get given that information, so there's no point the light
generating it.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Mon, 11 May 2009 12:20:56 +0100, Tim S wrote:

I'll have an LED TV when they become cheap/big enough

Big isn't a problem, is a 12.8m x 7.2m 1280 x 720p screen big enough?

Weight and cost might be though. B-)

http://www.adi.tv/rental/products-i100.html

--
Cheers
Dave.

Dave Plowman (News) wrote:
In article ,
William Sommerwerck wrote:
And the same will apply to LED backlights. It's a big con that
LEDs are more efficient -- they only are where supplying narrow-
bandwidth light. As soon as you try and make them produce
continuous-spectrum light -- ie white -- the efficiency goes way
down. Of course, they may improve -- but then again, so may
fluorescent.

White LEDs are not continuous-spectrum. They contain a phosphor that
produces yellow light when stimulated by blue light.

Indeed. So not suitable for where you need a decent quality light. As for
an LCD backlight.

Be careful. A lot of backlighting technology being developed is not
based on traditional LEDS but on variations of OLED. The emission
spectra can be radically different. Not saying tis so here, but it might be.

I was briefly involved with an OLED company trying to do this sort of
thing: There are many ways, including UV-LED and phosphors..

Dave Plowman (News) wrote:
In article ,
Arfa Daily wrote:

Just had one of those weekly e-ads from a local department store that we
use sometimes, trumpeting the latest "Ultraslim LED TV" from Samsung.

Ha! I thought. I haven't heard anything about this. Is it OLED ? At
sizes up to over 50", that didn't seem likely, so I followed the links
to see what it was all about.

Seems that these sets still actually have an LCD display panel, but the
*backlighting* is LED ...

Yup. There are what can be accurately described as LED TVs on the horizon
- OLED. But are some way off in normal sizes at an affordable cost.

OK, so I can see that there are advantages size-wise - these things
are only 32mm thick - and also power consumption savings, as we all know
that flourescent tube backlighting is very inefficient, but is it right
to actually call these "LED TVs"

Who says fluorescent is inefficient? LED could be better if you could turn
off those in the dark parts of the picture - but no claims for that.

Thats the point of it AIUI. And you can modulate each LED to the
lowest output pixel that it illuminates (dont know if that tv does
that). More contrast, but it messes with the ability to calibrate
colours - which doesnt much matter for a consumer TV.

The flip side is that LED is a lot less efficient than CCFL. Which
option consumes less I dont know.


Other
problem with LEDs is producing a continuous spectrum smooth white light -
needed to give all the colours from LCD.

I doubt any TV ever made has done that, nor is there any need to.


? Seems like a bit of a deliberately misleading use of the terminology
to me - or is it maybe just me being a picky grumpy old sod ? d:~)

Might as well claim any TV is LED - if it has an LED warning light. ;-)

I once bought a radio that proudly proclaimed 'transistor' on the
front. It did indeed have one transistor, in an otherwise valve set.


NT

Arfa Daily wrote:
Seems like a bit of a deliberately
misleading use of the terminology to me - or is it maybe just me being a
picky grumpy old sod ? d:~)


I've just written a reply to you, then decided not to post it as they
have better lawyers than me.

Andy

In article ,
Dave Platt wrote:
In article ,
Dave Plowman (News) wrote:

And the same will apply to LED backlights. It's a big con that LED are
more efficient - they only are where supplying narrow bandwidth light.
As soon as you try and make them produce continuous spectrum light - ie
white - the efficiency goes way down. Of course they may improve - but
then again so may fluorescent.

You're assuming that the designers use LEDs to create
continuous-spectrum light, and then pixel-filter this down to the R/G/B
pixels.

My understanding is that this is *not* what they're doing. Rather, I'm
told that they use a matrix of individual narrow-emission R/G/B LEDs,
which backlight the R/G/B-filtered LCD pixel "shutters".

If you use narrow emission LEDs, then all you'll get is those colours.

With proper selection of the R/G/B LED wavelengths (e.g. pick them with
peak output wavelengths close to the peak-optical-sensitivity
wavelengths of the photopigments in the human retina) you ought to be
able to get very good efficiency.

Sod the efficiency - I want decent flesh tones. ;-)

--
*Horn broken. - Watch for finger.

Dave Plowman London SW
To e-mail, change noise into sound.

If you use narrow-emission LEDs, then all you'll get
is those colours.

LEDs are by nature narrow-emission -- the wavelength is determined by the
band gap.

It wouldn't be horribly difficult to get the band gap set to come close to
the desired primary hues.

In message , William Sommerwerck
writes
If you use narrow-emission LEDs, then all you'll get
is those colours.

LEDs are by nature narrow-emission -- the wavelength is determined by the
band gap.

It wouldn't be horribly difficult to get the band gap set to come close to
the desired primary hues.


Really ?

--
geoff

In message , "Dave Plowman (News)"
writes
In article ,
Dave Platt wrote:
In article ,
Dave Plowman (News) wrote:

And the same will apply to LED backlights. It's a big con that LED are
more efficient - they only are where supplying narrow bandwidth light.
As soon as you try and make them produce continuous spectrum light - ie
white - the efficiency goes way down. Of course they may improve - but
then again so may fluorescent.

You're assuming that the designers use LEDs to create
continuous-spectrum light, and then pixel-filter this down to the R/G/B
pixels.

My understanding is that this is *not* what they're doing. Rather, I'm
told that they use a matrix of individual narrow-emission R/G/B LEDs,
which backlight the R/G/B-filtered LCD pixel "shutters".

If you use narrow emission LEDs, then all you'll get is those colours.

With proper selection of the R/G/B LED wavelengths (e.g. pick them with
peak output wavelengths close to the peak-optical-sensitivity
wavelengths of the photopigments in the human retina) you ought to be
able to get very good efficiency.

Sod the efficiency - I want decent flesh tones. ;-)


Pervert

--
geoff

On 11 May, 17:40, Jeff Liebermann wrote:
On Mon, 11 May 2009 12:12:08 +0100, "Arfa Daily"

wrote:
...but is it right to
actually call these "LED TVs" ? Seems like a bit of a deliberately
misleading use of the terminology to me - or is it maybe just me being a
picky grumpy old sod ? * *d:~)

Do you really want an LED screen very high res has pixel pitch of 5mm
so it does help to be on other side of football field for viewing.

Sure. *You've just been LED astray.
(Sorry, I couldn't resist).

I notice that Samsung's web pile conveniently does NOT mention
anything about the technology used in their Luxia line of TV's.
They've even dropped the Luxia name, preferring to use "LED TV"
instead. *My suspicious mind suggests that this seems intentional.
http://www.samsung.com/us/productsubtype/led/

Perhaps it would be helpful to refer to Samsung TV's by their
backlighting. *The ordinary LCD panel TV can be known as "CCFL TV".

Added sci.engr.lighting

As for improved efficiency, I'm wondering if that's true. *CCFL lamps
belch about 80-100 lumens/watt. *

Don`t think they do, very good fluro mebbe but don`t think cold
cathode gets an A for efiiciency.

Typical white LED's do 10-20
lumens/watt. *

Someone needs to get a modern white LED, even out the front fixture
efficiency is above 50 lW nowadays

Adam


http://en.wikipedia.org/wiki/Light-emitting_diode#Efficiency_and_oper...
http://en.wikipedia.org/wiki/Fluorescent_lamp#Luminous_efficacy
To get the same light output, LED's need to about 4-5 times as much
power. *If Samsung used the new and recently demonstrated high
efficiency white LED's, at 100 lumens/watt efficiency, they would at
best be equal to the efficiency of CCFL. Unless my arithmetic is
faulty, an common white LED backlit TV would belch MORE heat than a
CCFL backlit TV for the same brightness. *In addition, the smaller
physical size (thickness) of the LED backlit TV leaves less area for
ventilation and conductive cooling. *Looking back at the
"specifications" pages, on the Samsung web pile, I don't seem to find
a power consumption figure. * Oh-oh....

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

wrote in message
...
It does not require a continuous spectrum of light, however it must
have certain wavelengths. It may require a trip to a textbook to
understand it fully, but I will make an attempt.

You have explained nothing about the spectral character of the light that is
used to create a display. You may need to consult a text yourself to get a
better understanding of color science as applied to video. Poynton's text
is a good place to start. Your discussion relates mostly to the choice of
white points. This is one aspect of color reproduction. You are correct in
stating that any color (within the gamut defined by the primaries of a
device) can be made from combinations of three primaries. This is only part
of the story. The way that you mix those primaries to get those
intermediate colors and secondaries has everything to do with the spectrum
that they can create, as well as the assumptions that are made when the
source material is recorded and encoded. To get a good understanding of the
matter, you need to understand the basics of color science, which really
begins with the CIE standards and involves understanding the current
standards for video production and display such as the ITU rec.709 standard
for HD.

However, I suspect there is some actual white enhancement going on in
some LCD units, and as many are aware, the color wheel in a DLP
frequently has more than the three primary colors. I say this because
after observing the display on one of those Zeniths which had a bad
(and removed) blue polarizing filter, it could still reproduce white.

The color of white (gray) has specific colorimetry in the standards for
video. Most manufacturers deviate greatly from these standards and start
with OB settings that contain nearly twice as much blue as the standards
suggest, and this is regardless of the technology. When we calibrate
displays we bring them back to the standards to produce colors more
accurately. In the case of your Zenith example, the filter on the blue was
likely a polarizing filter or a UV filter. If you remove the UV protection,
you will shorten the life of the blue panel dramatically, and if you remove
the polarizer, you will compromise the brightness and black level control.

Red green and blue are defined scientifically as primary colors. I
don't know where those standards came from, nor do I care, but they
are there.

Some people do care, and those are the ones for whom a discussion of correct
color reproduction matters. For the large majority of the public, there is
no reason to buy one of these more expensive LCD sets when they would be
perfectly happy with something priced half or a third the price of these
high end units that have local dimming LED backlighting. For those that
care, the jury is still out on the LCD sets. The are getting close, and are
far better than many lower end PDP, DLP, and CRT based displays. There is
much variation within and between technologies, as with brands.

Leonard

"Andrew Gabriel" wrote in message
...
In article ,
"Leonard Caillouet" writes:
"Andrew Gabriel" andrew@a20 wrote in message
...
In article ,
"Dave Plowman (News)" writes:
In article ,
William Sommerwerck wrote:
And the same will apply to LED backlights. It's a big con that
LEDs are more efficient -- they only are where supplying narrow-
bandwidth light. As soon as you try and make them produce
continuous-spectrum light -- ie white -- the efficiency goes way
down. Of course, they may improve -- but then again, so may
fluorescent.

White LEDs are not continuous-spectrum. They contain a phosphor that
produces yellow light when stimulated by blue light.

Indeed. So not suitable for where you need a decent quality light. As
for
an LCD backlight.

I don't see why an LCD backlight needs to be anything other than
red green and blue, and having just checked one, that's exactly
what it is -- actually very much narrower bands than a regular
fluorescent, and without any of the other fill-in colours you
get from a fluorescent lamp. After all, anything else from the
backlight would be wasted (or worse, might bleed through into
some colour cells and contaminate the primary additive colours).

Y
That depends on the assumptions you make in the production of the source
and
the decoding to those narrow spectrum RGB displays. You may or may not
end
up with the same distribution of secondary and intermediate colors. The
human eye perceives color over a spectrum approximated by the CIE
standard
observer curves. Concentrating all of the energy at narrow bands can
have
some very significant effects, not only in overall brightness, but in
color
reproduction. While it is true that any color (within a given gamut) can
be
made up of a combination of narrow band RGB display sources, getting the
right spectral power at a given color requires mapping from what the
pickup
and encoding assume to what the display can produce. Unfortunately,
there
are not many good options for measuring response at colors other than
primaries and secondaries and no good standards for evaluating
performance
objectively at this time for intermediate colors, much less for those
colors
over a range of luminance values.

I agree, but the data is already split into RGB components before it
gets to the monitor. The monitor can't make up the colours inbetween;
it doesn't get given that information, so there's no point the light
generating it.

The display can and does make the colors in between from combinations of the
primaries. It DOES get the information on the mix of those colors but that
information is based on assumptions about how the display will produce the
image. When an engineer designs a camera, they are trying to match the
output of R,G,& B to the Standard Observer curves, not filtering it to
narrow band output at a particular frequency. When the color matrix in the
display recreates that RGB information, it contains the mix that will
produce the intermediate colors. If the display only produces a narrow
spectrum for each primary, the maker of that display has to account for that
in the color decoder and map the colors to what the display can create. It
can create the same colors but the mix to get any particular color may be
very different than a standard matrix calculation would produce if the
spectrum of the display primaries is very narrow compared to the CIE curve
( or CRT monitor response) upon which a camera is calibrated.

The bottom line is, there is more to the story than you are assuming.
Manufacturers get it closer or not, it depends on the execution of their
particular flavor of the technology.

Leonard

Dave Plowman (News) wrote:
In article ,
William Sommerwerck wrote:
Who says fluorescent is inefficient? LED could be better if you could
turn off those in the dark parts of the picture -- but no claims for
that.

Quite the contrary. Many LED sets use local dimming to improve image
contrast.

No claims for that I could see. If it does can only be a good thing as it
could give truer blacks as well - a problem with any backlit device.


Other problem with LEDs is producing a continuous spectrum smooth
white light -- needed to give all the colours from LCD.

The last thing you want is a continuous spectrum.

Eh?

Ideally, you want the R, G & B spectrum of the backlight to match the R,
G & B spectrum of the LCD pigments. That'll give you a spectrum with
three big spikes in it.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

wrote:
Now I am fully aware that there have been seven color printers, but
such enhancements are simply not practical for display technology.
That's the rules of the game, I didn't make them. Actually I haven't
seen a seven color printer for quite some time, they may have
abandoned the technique.

No, it's standard on high end inkjet printers, & some use even more than
7 inks. For example, the Epson Stylus Pro 3800 uses 8 inks.

I suspect it may just be too expensive, and
think of what something like that would do to the cost of a TV set or
monitor.

It's certainly impractical for screens, yes.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

In article ,
Bob Larter wrote:
wrote:
Now I am fully aware that there have been seven color printers, but
such enhancements are simply not practical for display technology.
That's the rules of the game, I didn't make them. Actually I haven't
seen a seven color printer for quite some time, they may have
abandoned the technique.

No, it's standard on high end inkjet printers, & some use even more than
7 inks. For example, the Epson Stylus Pro 3800 uses 8 inks.

I suspect it may just be too expensive, and
think of what something like that would do to the cost of a TV set or
monitor.

It's certainly impractical for screens, yes.

There's no need for a display since it is theoretically possible to get
all visible colours from RGB. Mixing dyes is a different matter.

--
*What happens if you get scared half to death twice? *

Dave Plowman London SW
To e-mail, change noise into sound.

snip

There's no need for a display since it is theoretically possible to get
all visible colours from RGB. Mixing dyes is a different matter.

--
*What happens if you get scared half to death twice? *

Dave Plowman London SW
To e-mail, change noise into sound.


Theory, remembered from many years ago, suggests that isn't quite true. I
seem to recall my colour TV lecturer at college, spending a whole session on
'the chromaticity diagram', and then explaining that there were certain
'non-spectral' colours such as brown, which could not be created by an
additive mix of R,G and B, and any brown that was seen on the screen was
actually some kind of orange or red, which was *perceived* as brown because
of the surrounding colours, and other visual cues. That might not be exactly
it, as this was all learnt nearly 40 years ago, but something close, I
think.

As to whether LEDs as backlights do a good job, I'm sure that they must be
at least as good as CCFLs at colour rendering, otherwise, the manufacturers
wouldn't be making such a thing about it. Flesh tones look perfectly fine on
digital cameras which use LED backlit displays.

My whole issue with this, was that the LED 'angle' was being pushed by
wording that *suggested* it was the main display technology rather than an
LCD panel which it actually is, and which the great unwashed are now
familiar with. That seemed to me to be a deliberate attempt to mislead
people into believing that it was something new and revolutionary - as SED
technology will be if it ever gets on the market, or OLED if they can get it
big enough.

I don't have a problem with them claiming that this backlighting technique
is revolutionary in TV sets - it is - and even claiming a reduction in
power, if that's true, for a leg-up on the eco-bollox ladder, but I really
think that they should be making that distinction, rather than trying to
bamboozle prospective buyers with questionable use of terminology which
punters are likely to have heard of, but won't actually understand.

On the power consumption issue, I still do not feel that this technology is
likely to consume anything like as much as the 100 or so watts that CCFL
backlighting does. The developments in the light output of narrow-angle LEDs
over the last couple of years is staggering. Some of the 1 and 3 watt types
could literally blind you. I believe that some cars are now starting to use
LED headlamps. It would be interesting to see how they stack up against the
50 watt consumption of 'standard' headlamp bulbs.

Arfa

Dave Liquorice wrote:
On Mon, 11 May 2009 12:20:56 +0100, Tim S wrote:

I'll have an LED TV when they become cheap/big enough

Big isn't a problem, is a 12.8m x 7.2m 1280 x 720p screen big enough?

Weight and cost might be though. B-)

http://www.adi.tv/rental/products-i100.html

You could make some kids' day with that, the way these folks did:
http://www.youtube.com/watch?v=_Nbkbss7i5s

Cheers

Phil Hobbs