colour temp can be controlled using the LEDs or the LCD, I'm not sure it makes any big difference which one.
RGB LEDs would give the same white as a triphosphor&uv white LED, but with more colour control. The standard 2 colour white LED would be useless on a 3 channel display. And fwiw bichromic white LEDs have huge colour balance variation, way outside of whats acceptable for a display.
NT
In a very broad sense, the last thing you want is a "full-spectrum" light. The standard primaries are diluted with too much white as it is.
Which is why, given that they've put these LEDs under at least some kind of control in order to implement their (claimed) enhanced black reproduction scheme, that I was questioning whether the scheme maybe allowed for a degree of user intervention under the guise of "tint" or whatever, and which might have accounted for why on this particular TV - the only example that I've seen on and working so far - the flesh tones were so poor compared to Pan and Sony offerings in the same display stack, showing the same picture. I'm trying to get a handle on why a company with the products and reputation of Sammy, are a) using advertising terminology that appears to be questionable in the context that it appears, and b) producing a set, claiming it to be the dog's bollocks of display technology, which does not appear - to my eye at least - to be as good as their traditionally CCFL backlit offerings, or those of other manufacturers.
I saw the latest all singing and dancing LCD HD Pan, just released, in my friend's shop yesterday. Uses conventional CCFL backlighting. Not as thin as the Sammy, but getting there. Apart from the usual slight gripes that you could direct at any LCD panel when examined closely, the picture was quite stunning, and the colour rendition was as close to 'perfect' as you could reasonably expect. Certainly, flesh tones *appeared* accurate, but I accept that is subjective. Anyway, whichever-whatever, more accurate than they appeared on the LED backlit Sammy ...
Arfa
I guess it comes down to definitions and how 'full spectrum' is perceived. Rightly or wrongly, I tend to think of it as a spectrum which contains the same component colours in the same ratios, as natural daylight, but I guess even that varies depending on filtering effects of cloud cover and haze and so on. Even so, I'm sure that there must be some definition of 'average spectrum daylight', and I would expect that any display technology would aim to reproduce any colour in as closely exact a way as it would appear if viewed directly under daylight. I'm sure that the LCD 'primary' filters are probably not linear in their transmission characteristics, but probably close enough that you could use a backlight which contained a similar spectrum to daylight, and filters 'tuned' to the RG and B humps. All pure guesswork of course, as it's not my field ...
Arfa
That's a reasonable definition for a video display, but it's not sufficient for source lighting. It's difficult to make a "full spectrum" fluorescent lamp, especially one that produces good color rendition for photograpy.
The standard is D6500, a 6500K continuous spectrum from a black-body source. What you suggest is, indeed, the intent.
TBH I think this is overplaying the significant of daylight. Almost any monitor is adjustable to suit preferences of anything from 5000K to 10,000K, and some go lower. None manke any attempt to copy the colour spectrum of daylight, they merely include the same colour temp as daylight as one of the options. None of the major display types have any ability to copy a daylight spectrum, as they're only RGB displays.
NT
fluorescent
I think you've missed the difference between recreating the original color (or the illusion of same), and producing a photographically useful illuminant. These are different.
But take account of the fact that we're talking domestic television sets here, not computer monitors. For the most part, TV sets do not display the same type of content as a computer monitor, and do not include user accessible colour temperature presets or adjustments, which is why I made the point earlier that in general, LCD TVs are set correctly 'out of the box'.
As far as overplaying the significance of daylight goes, I'm not sure that I follow what you mean by that. If I look at my garden, and anything or anybody in it, the illumination source will be daylight, and the colours perceived will be directly influenced by that. If I then reproduce that image on any kind of artificial display, and use a different reference for the white, then no other colour will be correct either, which was ever the case when CRTs were set up to give whites which were either too warm or too cold, even by a fraction. Maybe we're talking at cross purposes here, or I'm not understanding something properly, but it seems to me that the colour temperature and CRI of the backlighting on an LCD TV, would be crucially important to correct reproduction of colours.
All I know is, is that the flesh tones were poor on the example that I saw, compared to other LCD TVs which were showing the same picture. The fundamental difference between those sets and the Sammy, was the CCFL vs LED backlighting, so it seems reasonable to draw from that, the inference that the backlighting scheme may well be the cause, no ?
Arfa
Every lcd TV I have seen has colour temp adjustments.
>
What, readily user accessible ?
Arfa
I have no idea of UK law, but in the US and here in Israel, if they use LED's in the display, then they can call it an "LED TV". I expect the same in the UK, I was watching a show from the first season of "The F Word" (things take a long time to get here) and they were discussing exactly what could be called a sasuage in the UK. Based on what I saw, I expect you would have trouble fighting them calling a TV with a power on LED an LED TV. :-(
In theory, yes they can. Since LCD's have very limited control over brightness then a variable brightness LED behind an LCD will allow them to modulate the light level of that particular pixel.
I don't know the resolution of the LCD array used in a TV set, but at the actual crystal level, it's clear (on edge) or colored/transparent (face out). I guess if you modulated the polarizing signal you could get levels of color out of them, but I thought that the crystals were not fast enough for that.
Is there really such a thing as a white LED? The ones I have seen have all been red/green/blue LEDS on the same substrate to produce what appears to the eye as a white beam, most of which are far too blue for my taste.
They are blue because blue LEDs have a much shorter life than red and green so the color will change as they age, and they start out blue before the end up a red green mix (yellow/orange).
That may be a different story because PAL TV sets never had them. NTSC sets needed them because the phase of the color carrier wandered and often shifted to the green, while PAL sets reset the phase each line and therefore were always "correct".
Since the chroma signal of an MPEG encoded TV signal does not pass through a phase encoder unless you connect a composite or RF monitor, it seems unlikely any sets would have them. More likely, ones sold to people who are used to PAL over the air signals don't and people used to NTSC ones do.
I have yet to be impressed by an LCD/PLASMA TV. Every single one of them I have seen is oversaturated and too bright.
Geoff.
It depends on where you leave the remote.
You havent defined what you mean by a 'photographically useful illuminant'
NT
fwiw my main set does, and I'm sure its not unique. Generally though a TV is a much lower quality animal than a monitor, and displays much lower quality data.
because they can be. CRTs are more variable, and the circuits used to drive them a lot less precise, partly because CRT sets are generally older, and the sort of standards expected in monitors have only begun crossing over to tvs in recent years.
what makes you think that just one specific colour temp is 'correct'? Real daylight is all over the place colour temp wise, and the end user experiences those changes without any problem. Also any self respecting monitor offers a range of colour temps, since its nothing but a taste matter
but thats down to historic reasons, customers never expected precise colour temp, and screens were routinely set up by eye. The circuits involved couldnt set themselves up the way a modern LCD set can, there was normally no feedback on colour channels, just open loop CRT gun drive on top of a massive dc offset, so the systems were inherently variable. Plus the fact that CRT gamma was often way off from the real world made it hard, or should I say impossible, to set such sets to give a faithful reproduction in other respects anyway.
It has almost nothing to do with it, because the level of each colour channel output on the screen depends on both the light source and the settings of the LCD R,G,B channels. Within reason, any temperature colour backlight can produce any temperature colour picture.
Its just a guess. In fact any desired flesh tone can be reproduced using almost any colour temp backlight, certainly anything from 3,000K to 10,000K. Think about the process, you've got 3 colour channels, each of which has a given level of light from the backlight, which is then attenuated to any desired degree by the LCD pixel.
NT
It depends on what you define as a color temperature adjustment. Many (if not most) sets do not have the detailed adjustments that make possible both correct color temperature and good grayscale tracking. When they do, these are not usually available to the customer.
Have you never seen the ones that use a blue LED and a yellow-fluorescent pigment?
What?
I have never seen a dead LED (though I assume they exist), nor have I heard of LEDs becoming dimmer with age.
NTSC does not, and never had, an inherent problem with phase stability.
Because you're seeing them in "torch" mode. There are plenty of good sets out there. Find a dealer with a Pioneer plasma set, have him put on a really good disk, and be prepared to die.
It isn't if you want an accurate rendition of the program material.
I was about to jump on that, but it's basically correct. However, you'd want the backlight to be "reasonably close", so you didn't have to push any channel to its limits of adjustment.
Not really. Transparencies subtract some colours from the transmitted light; prints subtract some from the reflected light. Displays make their own...
Andy
thats only true if you mean you want to watch it at the same colour temp. Most people neither know nor care, and real world TVs are set to an assortment of differing colour temps.
... not really. The backlight on this monitor is far removed from the colour temp its operating at, and all is well. When its far removed it does affect contrast ratio a bit.
NT
I have to disagree. Suppose the backlight doesn't produce sufficient blue for the desired color temperature. You can compensate by displaying the blue pixels at a higher luminance level. But you can't go higher than 100% -- the lightest (highest) level the LCD can transmit. That level might not be enough to match the green and red levels.
A roughly similar situation occurs with color-negative film. If you expose daylight-balanced film at 2800K, the blue layer might be unacceptably underexposed, and no amount of additional blue-layer exposure during printing will restore the lost shadow detail. Ditto for exposing 3200K film under daylight, except the error is on the side of overexposure.
Simply stated, neither an LCD nor photographic film can display or record an infinite brightness range.
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