Bit of a Con Really - Follow-up ...

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?

green

end up

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 in the slightest. Do you even understand the difference between digital and analog? Put a USB signal from a DMM on a scope and compare that to the input signal and then get back to us how they are so similar.

That's analog. Did you never learn that video displays use a video dac to generate analog voltages for driving an analog monitor?

Not really. Transparencies subtract some colours from the transmitted light; prints subtract some from the reflected light. Displays make their own...

Andy

What has that have to do with what I said?

If you look at the DECODED signal, which would be a stream of numbers, one defining a luminance level and the other defining a color, and displayed them using an appropriate method, it would look a lot like an analog signal displayed the same way.

You are confusing ENCODED data with DECODED data.

Let's take your example, A DMM with a USB output sends out a data stream of samples. These samples are encoded as numbers, let's say 32 bit signed integers, stuffed into packets and the packets have USB handshaking and other data transmission information wrapped around them. Looking at the USB output of the DMM (which would be ENCODED data) you would see very little that resemebled the input.

Now if you stripped off all the USB handshaking and control information, and recombined the packets into a data stream, what would you see? If you used that for a histogram or "osciloscope display" ala Winamp, the DECODED data would look a lot like the original signal. (depending upon sampling rate, etc).

Now, back to the TV signal. Since it an MPEG (any level) encoded stream contains individual pixels as samples of luminance (brightness) and chroma (color), if you were to display it as a histogram, let's say vertical lines being brightness and each line colored according to the chroma (color), then if you did the same thing to an analog signal, they would look awfully close.

Geoff.

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

The comment that I quoted with the ridiculously idiotic statement that digital streams look like analog.

Moving the goalposts? Pathetic.

That isn't the way an MPEG is encoded. It's rather more complex.

Furthermore, as most (though not all) color-encoding systems use some combination of luminance and color-difference signals, it follows that, on a basic level, DVDs, BDs, NTSC, and PAL -- not to mention JPG -- are very much alike. Claiming there's an interesting similarity doesn't tell us something we don't already know.

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.

Ah, so that is why they are backlit then?

So they can 'make their own? What a prat. An LCD display IS a color transparency.

In the case of an LCD display, that is correct. However, I expect his intended meaning was CRTs, Plasmas, OLEDs, proper LEDs, and SEDs, all of which *do* "make their own" ...

Arfa

Considering the litiginous nature of U.S. society, and some of the consumer product cases that William cited in a thread from a few months ago (Canderel sugar substitute was it ? Something like that anyway) I'm surprised at that. Also, Ramsay and his sausages is probably more of the exception than the rule nowadays in the UK. Since handing over the running of our nation in every way possible to faceless wonders in Brussels, we are so bogged down in legislation about what we can and can't say about products that we can and can't sell in ways that they dictate, I'm sure that someone will jump on this sooner or later to say that unless it's at least 72.65% LEDs, you can't call it a "LED TV" d;~}

I think that I would have to contest your point of "very limited control". All of the (recent) half-way decent LCD screens that I have seen to date, have a perfectly adequate contrast ratio. Certainly, the one in my kitchen produces deep enough blacks and bright enough whites to be absolutely fine under the pretty intense flourescent light that I have in there. This is one of the reasons that I question the requirement to extinguish areas of the backlighting in order to 'improve' the rendition of blacks.

With HD now, the resolution of the panels is high, and the speed of them is enough to cope with 100Hz refresh rates

White LEDs do exist in a form that is not RGB based, and in fact is the commonest form of them. They are blue LEDs with a yellow phosphor overlaid. There is a wide variety of 'colours' of white available, including ones that are distinctly bluish, and ones that are yellowish.

Well actually, the one in my kitchen isn't, neither is the one in my daughter's lounge. The new Pan that I saw Friday in my friend's shop, was excellent in that respect, giving an extremely nicely 'balanced' picture. There are aspects of flat panel displays which cause me to like them less than CRTs, but 'general' picture quality in terms of brightness, contrast etc, is not one of them. I think that in general, they've got that one nailed down now.

Arfa

You're not quite correct there. They do dim with age, and that is actually the way that they are specified for lifetime expectancy. I seem to remember that it is something like 'hours to the 50% point'. The figure drops drastically if they are DC driven rather than pulse driven, and if they are 'abused' with excess current. I have also seen dead LEDs in indicators, bargraph displays, and where they are used as some kind of voltage reference in amplifier output stages.

Arfa

If you're just watching casually under high ambient lighting, the quality of the blacks is pretty irrelevant. It's when you're doing some serious viewing under subdued lighting that it matters. And this is exactly where ordinary backlit LCD falls over against CRT.

Dear me. Got out of bed the wrong side today? You do seem to be getting a little impolite lately! Anyway...

Unlike a slide (usually shown with a halogen lamp) or a print (usually shown under whatever ambient light is about) most LCD displays have a backlight specially chosen by the manufacturer to meet some compromise of (good colour, cheap, low power, probably something else I can't think of) when operating with the particular LCD filters in front of them.

A slide has a pretty good match to the colours of the real scene. It has to, because the slide manufacturer didn't make the projector.

There's no such requirement for a display - it's the light emitted by the entire combination of backlight and filters that matters.

OK?

Andy

Granted, but this is a general entertainment device. When does anyone do any 'serious' viewing on a TV set, especially a not-very-special 32" LCD ? These things are designed to have Coronation Street watched on them in normal, averagely lit lounges really. I've seen some of the Sony offerings that are intended as 'serious' home cinema displays, displayed in subdued lighting demo rooms. One that I was particulary impressed by, was in a Sony store in Vegas. That set had standard constant intensity CCFL backlighting, and I don't recall thinking that there was any problem at all with the way it rendered blacks. Have you had a look at one of these LED backlit Sammys yet Dave ? As you are involved with the broadcast business - allbeit on the sound side rather than the vision - I would be interested to know what you make the picture compared to others. Waitrose have them, so I guess John Lewis would as well, as well as the Currys barns, probably.

Arfa

That's not really right...

The color rendition of a transparency -- or print -- is intended to be "correct" under a specific illuminant, usually one with a continous spectrum, at a specific color temperature.

For the colors in a print or transparency to be "correct" in any absolute sense -- that is, to actually "match" the colors of the original scene -- they would have to have the same spectral characteristics. They rarely do. And they don't have to, if the way the eye is stimulated is close.

Exactly the same thing applies to prints and transparencies. What the eye & brain think they see is all that matters.

Nope. See preceding.

Me, for one. Some things I like to watch properly - not just glance at. And it's not so very long ago a 28" CRT was pretty well top of the range. But when I do sit down to watch TV I do it under controlled lighting conditions - and through a good stereo sound system too. I want to see it at its best.

Maybe, but then so was every TV ever made.

No - I'm not in the market for a new TV yet.

All I do know was I worked on an HD TV shoot recently where the monitors were all LCD HD (and Pro ones so I assume state of the art). And on the numerous night scenes the LD was relying totally on his scope to set black level rather than the monitor. Which was displaying various shades of grey where it should have been black. Quite a 'contrast' from the Grade 1 CRT location monitors which were used for SD.