Bit of a con, really ... ?

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
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Arfa Daily coughed up some electrons that declared:

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
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Arfa Daily coughed up some electrons that declared:

This is more descriptive, though the tile seems misleading:
http://www.comet.co.uk/shopcomet/advice/640/Samsung-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/detail/detail.do?group=television&type=television&subtype=ledtv&model_cd=UE40B7020WWXXU&pid=uk_home_c1r2contents_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/2009/01/26/review_lcd_tv_samsung_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.
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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.

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.

Might as well claim any TV is LED - if it has an LED warning light. ;-)
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On Mon, 11 May 2009 13:28:06 +0100 "Dave Plowman (News)"

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.
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It was crap in all respects and ended up being sold off in bargain basement stores.
MBQ
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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
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Quite the contrary. Many LED sets use local dimming to improve image contrast.

The last thing you want is a continuous spectrum.
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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.

Eh?
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Dave Plowman (News) wrote:

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.
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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
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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.
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White LEDs are not continuous-spectrum. They contain a phosphor that produces yellow light when stimulated by blue light.
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Indeed. So not suitable for where you need a decent quality light. As for an LCD backlight.
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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).
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wrote:

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
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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.
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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
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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.

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.

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
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snipped-for-privacy@aol.com wrote:

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.

It's certainly impractical for screens, yes.
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