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

Reply to
Arfa Daily
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Arfa Daily coughed up some electrons that declared:

This by any chance?

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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

Reply to
Tim S

Arfa Daily coughed up some electrons that declared:

This is more descriptive, though the tile seems misleading:

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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:

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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.

Reply to
Tim S

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. ;-)

Reply to
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.

Reply to
JW

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

Reply to
Arfa Daily

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

The last thing you want is a continuous spectrum.

Reply to
William Sommerwerck

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

MBQ

Reply to
Man at B&Q

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.

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.

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....

Reply to
Jeff Liebermann

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

Reply to
William Sommerwerck

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.

Reply to
Dave Plowman (News)

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?

Reply to
Dave Plowman (News)

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

Reply to
William Sommerwerck

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

Reply to
Dave Plowman (News)

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.

Reply to
Dave Platt

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.

Reply to
Dave Platt

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

Reply to
Leonard Caillouet

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).

Reply to
Andrew Gabriel

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

Reply to
Leonard Caillouet

Philps has a TV that does this...

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

Darren

Reply to
dmc

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