Bit of a Con Really - Follow-up ...
 

Arfa Daily wrote:
Yes Geoff, I'm aware of all that. I work with the technology all the time.
Did you read the original thread from last week ? We were not discussing the
differences between transport and encoding systems, rather the moral - if
not technical - validity of Sammy advertising this new offering of theirs as
a "LED TV", which it isn't. It's an LCD TV with an alternate form of
backlighting (LEDs rather than CCFL).

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. :-(



One of the main selling points that they claim, is that because they can
control the intensity of the backlighting in individual areas, they can
deepen the blacks, effectively improving the contrast ratio.

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.


On the example
that I saw last night, I observed no such improvement that was obvious,
compared to the sets around it. The reason that I questioned what controls
for picture setup are available on this particular set, was that given that
the backlighting is formed by RGB LED arrays, not white LEDs, then the
overall colour temperature would in theory be adjustable - sort of a grey
scale adjustment for LCDs, if you like.

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).


If this was the case, it might be
accessible to the customer via the standard controls menu, as something like
"tint" or "hue", and the reason that this particular set (they only had the
one on display) did not seem to produce good flesh tones compared to the
sets around it, might be because some sales erk had been playing with the
controls to see if he could 'improve' it ...

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.

Someone - maybe William - commented last week in the original thread, that
they had seen one in Fry's in the U.S., and that they weren't especially
impressed, either.

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.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

Bit of a Con Really - Follow-up ...
 

"Arfa Daily" wrote in message
...

"dennis@home" wrote in message
...


"Arfa Daily" wrote in message
...


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'.

Every lcd TV I have seen has colour temp adjustments.



What, readily user accessible ?

It depends on where you leave the remote.

Bit of a Con Really - Follow-up ...
 

William Sommerwerck wrote:
wrote in message
...
William Sommerwerck wrote:

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...

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.


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.

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.

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.

You havent defined what you mean by a 'photographically useful
illuminant'


NT

Bit of a Con Really - Follow-up ...
 

Arfa Daily wrote:
wrote in message
...
William Sommerwerck wrote:
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...

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.


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.

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

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,

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.


which is why I made
the point earlier that in general, LCD TVs are set correctly 'out of the
box'.

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.


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,

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


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.

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.


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.

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.


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

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

Bit of a Con Really - Follow-up ...
 

"Geoffrey S. Mendelson" wrote in
message ...
William Sommerwerck wrote:

Mr. Mendelson has little understanding of how digital television works.
Rather than refute his points, I will urge him to find a book on the
subject
and read it.

Actually I do. Why don't you refute my points and that way I can refute
yours
instead of this becoming a ****ing contest.

First of all, your description ignores the compression systems used, and
treats digital TV more or less as if it is little more than a sequence of
digitized samples. It isn't.

I'm not sure why he makes a point about the lack of sync pulses, as their
lack is implicit in the way compressed video is stored and reconstituted.

Bit of a Con Really - Follow-up ...
 

Every lcd TV I have seen has colour temp adjustments.

What, readily user accessible ?

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.

Bit of a Con Really - Follow-up ...
 

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.

Have you never seen the ones that use a blue LED and a yellow-fluorescent
pigment?


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).

What?

I have never seen a dead LED (though I assume they exist), nor have I heard
of LEDs becoming dimmer with age.


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".

NTSC does not, and never had, an inherent problem with phase stability.


I have yet to be impressed by an LCD/PLASMA TV. Every single one of them
I have seen is oversaturated and too bright.

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.

Bit of a Con Really - Follow-up ...
 

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 it's nothing
but a taste matter.

It isn't if you want an accurate rendition of the program material.


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.

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.

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.

Bit of a Con Really - Follow-up ...
 

On Fri, 22 May 2009 09:24:03 +0000 (UTC), Geoffrey S. Mendelson wrote:
Arfa Daily wrote:

I don't know what 'set-ups' this TV has, in terms of brightness, contrast,
colour saturation, tint/hue, but in my experience, most LCD TVs - which is,
after all, what this is - are set correctly 'out of the box', but I accept
that this particular one that I saw might not be a good example of the
technology.

Based on the assumption that it is a PAL set probably brightness,
contrast, and maybe color saturation. Digital TV sets are not PAL per
se, but they still use the same luminance, color, sync, signals that are
used by PAL (and slightly differently by NTSC).

They are also still 25 or 30 frames per second depending upon whether or
not thay are interlaced as in 1080i or not. An interlaced frame is still
2 fields, at 50 or (almost 60Hz) combined.

The main differences between a digital TV signal and an analog one are that
since each frame is discrete, there really is no need for a syncronization
pulse to define the begining of each frame and more importantly, there is
no color subcarrier.

If you were to look at a digital TV signal decoded as if it were a
stream of pixels, you would see something that looked a lot like an
analog TV signal.

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.


Computer displays, BTW are red-green-blue with seperate horizontal and vertical
sync, which is very different.
That's analog. Did you never learn that video displays use a video
dac to generate analog voltages for driving an analog monitor?

Bit of a Con Really - Follow-up ...
 

The Natural Philosopher wrote:

Color transparencies which are used in pro film applications say your
are a liar.

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

Andy

Bit of a Con Really - Follow-up ...
 

AZ Nomad wrote:

If you were to look at a digital TV signal decoded as if it were a
stream of pixels, you would see something that looked a lot like an
analog TV signal.

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.

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.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

Bit of a Con Really - Follow-up ...
 

William Sommerwerck wrote:
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 it's nothing
but a taste matter.

It isn't if you want an accurate rendition of the program material.

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.


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.

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.

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. 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

Bit of a Con Really - Follow-up ...
 

On Sat, 23 May 2009 23:09:04 +0000 (UTC), Geoffrey S. Mendelson wrote:
AZ Nomad wrote:

If you were to look at a digital TV signal decoded as if it were a
stream of pixels, you would see something that looked a lot like an
analog TV signal.

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.

What has that have to do with what I said?

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


If you look at the DECODED signal, which would be a stream of numbers,
Moving the goalposts? Pathetic.

Bit of a Con Really - Follow-up ...
 

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.

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.

Bit of a Con Really - Follow-up ...
 

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. 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.

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.

Bit of a Con Really - Follow-up ...
 

Andy Champ wrote:
The Natural Philosopher wrote:

Color transparencies which are used in pro film applications say your
are a liar.

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


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.

Andy

Bit of a Con Really - Follow-up ...
 

"The Natural Philosopher" wrote in message
...
Andy Champ wrote:
The Natural Philosopher wrote:

Color transparencies which are used in pro film applications say your
are a liar.

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


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.

Andy

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

Bit of a Con Really - Follow-up ...
 

"Geoffrey S. Mendelson" wrote in message
...
Arfa Daily wrote:
Yes Geoff, I'm aware of all that. I work with the technology all the
time.
Did you read the original thread from last week ? We were not discussing
the
differences between transport and encoding systems, rather the moral - if
not technical - validity of Sammy advertising this new offering of theirs
as
a "LED TV", which it isn't. It's an LCD TV with an alternate form of
backlighting (LEDs rather than CCFL).

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. :-(


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;~}



One of the main selling points that they claim, is that because they can
control the intensity of the backlighting in individual areas, they can
deepen the blacks, effectively improving the contrast ratio.

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 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.


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.

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



On the example
that I saw last night, I observed no such improvement that was obvious,
compared to the sets around it. The reason that I questioned what
controls
for picture setup are available on this particular set, was that given
that
the backlighting is formed by RGB LED arrays, not white LEDs, then the
overall colour temperature would in theory be adjustable - sort of a grey
scale adjustment for LCDs, if you like.

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).



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.



Someone - maybe William - commented last week in the original thread,
that
they had seen one in Fry's in the U.S., and that they weren't especially
impressed, either.

I have yet to be impressed by an LCD/PLASMA TV. Every single one of them
I have seen is oversaturated and too bright.


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

Bit of a Con Really - Follow-up ...
 

"William Sommerwerck" wrote in message
...
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.

Have you never seen the ones that use a blue LED and a yellow-fluorescent
pigment?


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).

What?

I have never seen a dead LED (though I assume they exist), nor have I
heard
of LEDs becoming dimmer with age.


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

Bit of a Con Really - Follow-up ...
 

In article ,
Arfa Daily wrote:
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.

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.

--
*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.

Bit of a Con Really - Follow-up ...
 

The Natural Philosopher wrote:
Andy Champ wrote:
The Natural Philosopher wrote:

Color transparencies which are used in pro film applications say your
are a liar.

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


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.

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

Bit of a Con Really - Follow-up ...
 

"Dave Plowman (News)" wrote in message
...
In article ,
Arfa Daily wrote:
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.

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.

--
*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.

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

Bit of a Con Really - Follow-up ...
 

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

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.


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

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


OK?

Nope. See preceding.

Bit of a Con Really - Follow-up ...
 

In article ,
Arfa Daily wrote:
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.


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
?

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.

These things are designed to have Coronation Street watched on them in
normal, averagely lit lounges really.

Maybe, but then so was every TV ever made.

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

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

? 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.

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.

--
*Oh, what a tangled website we weave when first we practice *

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

Bit of a Con Really - Follow-up ...
 

"The Natural Philosopher" wrote in message
...
Andy Champ wrote:
The Natural Philosopher wrote:

Color transparencies which are used in pro film applications say your
are a liar.

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


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.

No it is not!

A transparency is a subtractive process.
An lcd is additive.

Each pixel in a film transparency has three filter layers each of which can
absorb a colour.

Each pixel on an lcd is made from three different colour subpixels.
The subpixels each have a colour filter behind them to make them RGorB.



Andy

Bit of a Con Really - Follow-up ...
 

In article ,
Andy Champ wrote:
So they can 'make their own?
What a prat. An LCD display IS a color transparency.

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

It's not a bad analogy.

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.

LCD backlights are usually chosen to have a pretty good spectral response.

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.

But then different makes of transparencies give different results...

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

How about LCD projectors?

--
*Why is it that to stop Windows 95, you have to click on "Start"?

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

Bit of a Con Really - Follow-up ...
 

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.


Is anyone making grade one CRT monitors or hi spec CRT's still?...
--
Tony Sayer

Bit of a Con Really - Follow-up ...
 

William Sommerwerck wrote:
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. 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.

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.

indeed, but you'd have to have a huge mismatch between backlight CCT
and displayed image CCT for that problem to occur. A 15,000K backlight
with a 5000K display works just fine.


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.

yes that happens with film, but nothing like it happens with an LCD
display. What happens is that if your image is far removed from the
backlight in terms of CCT, then one of the RGB LCD colour channels
operates over part of its potential range, not the full range. So for
example on this display the B pixels might never exceed 50% light
transmission. It doesnt cause a problem.


Simply stated, neither an LCD nor photographic film can display or record an
infinite brightness range.

of course


NT

Bit of a Con Really - Follow-up ...
 

William Sommerwerck wrote:

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".

NTSC does not, and never had, an inherent problem with phase stability.

I cant conclude anything, but I know 2 things:
1. NTSC is widely known as Never The Same Color twice
2. The PAL system includes measures to counter phase shift causing
colour issues, so I can only conclude that the system engineers
thought this was a problem with NTSC.

And fwiw, IIUC PAL rendered colours are designed to alternate the
error line after line rather than get each line colour correct, so
like many such measures it usually solves the problem, but not always.


I have yet to be impressed by an LCD/PLASMA TV. Every single one of them
I have seen is oversaturated and too bright.

isnt that just an adjustment thing? And yes, I agree many wont go dim
enough, but some do.


NT

Bit of a Con Really - Follow-up ...
 

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".

NTSC does not, and never had, an inherent problem with phase stability.

I cant conclude anything, but I know 2 things:
1. NTSC is widely known as Never The Same Color twice
2. The PAL system includes measures to counter phase shift causing
colour issues, so I can only conclude that the system engineers
thought this was a problem with NTSC.

I don't have the time to discuss this at length, but NTSC's unfortunate
reverse-acronym was the result of poor studio standards, and is not inherent
in the system. PAL incorporated phase alternation to partly compensate for
transmission problems (non-linear group delay) in Europe.


And fwiw, IIUC PAL rendered colours are designed to alternate the
error line after line rather than get each line colour correct, so
like many such measures it usually solves the problem, but not always.

Correct. That's why color errors roughly cancelled out, at the expense of
loss of satruation.

Bit of a Con Really - Follow-up ...
 

In article , William
Sommerwerck scribeth thus
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".

NTSC does not, and never had, an inherent problem with phase stability.

I cant conclude anything, but I know 2 things:
1. NTSC is widely known as Never The Same Color twice
2. The PAL system includes measures to counter phase shift causing
colour issues, so I can only conclude that the system engineers
thought this was a problem with NTSC.

I don't have the time to discuss this at length, but NTSC's unfortunate
reverse-acronym was the result of poor studio standards, and is not inherent
in the system. PAL incorporated phase alternation to partly compensate for
transmission problems (non-linear group delay) in Europe.


Wasn't something done to either the NTSC transmission spec or the sets
that largely alleviated that .. sometime after the original system
started?..


And fwiw, IIUC PAL rendered colours are designed to alternate the
error line after line rather than get each line colour correct, so
like many such measures it usually solves the problem, but not always.

Correct. That's why color errors roughly cancelled out, at the expense of
loss of satruation.



Simple PAL and de luxe PAL IIRC but it was a long time ago now;)..
--
Tony Sayer

Bit of a Con Really - Follow-up ...
 

Andy Champ wrote:
The Natural Philosopher wrote:
Andy Champ wrote:
The Natural Philosopher wrote:

Color transparencies which are used in pro film applications say
your are a liar.

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


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.

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

No transparency can show a spectral section that isn't in the spectrum
of the illuminant.

Which is why monochromatic backlights or projector light sources are not
used.

I challenge you to e.g. produce a natural colour with a sodium lamp..no
matter how you tweak the color dyes.

Bit of a Con Really - Follow-up ...
 

dennis@home wrote:


"The Natural Philosopher" wrote in message
...
Andy Champ wrote:
The Natural Philosopher wrote:

Color transparencies which are used in pro film applications say
your are a liar.

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


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.

No it is not!

A transparency is a subtractive process.
An lcd is additive.

Think again.


Each pixel in a film transparency has three filter layers each of which
can absorb a colour.


I've not heard of pixels with respect to film before. Make it up as we
go along?

Each pixel on an lcd is made from three different colour subpixels.
The subpixels each have a colour filter behind them to make them RGorB.

Which amounts to the same thing in practice.

50% on two colors and 0 on another in film = LCD primary.

As far as the eye is concerned. The issue being that the colours in all
cases are relatively broad spectrum colours. You cant get monochromatic
colour with either system if you want overall balance. You are not
mixing pure red, pure blue and pure green any more than you are notching
out everything BUT pure magenta pure cyan or pure yellow..





Andy

Bit of a Con Really - Follow-up ...
 

Dave Plowman (News) wrote:
In article ,
Andy Champ wrote:
So they can 'make their own?
What a prat. An LCD display IS a color transparency.

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

It's not a bad analogy.

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.

LCD backlights are usually chosen to have a pretty good spectral response.

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.

But then different makes of transparencies give different results...

And transparencies are usually used for top quality magazine prints not
'projected onto a screen' anyway.


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

How about LCD projectors?

Bit of a Con Really - Follow-up ...
 

William Sommerwerck wrote:
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".

NTSC does not, and never had, an inherent problem with phase stability.

I cant conclude anything, but I know 2 things:
1. NTSC is widely known as Never The Same Color twice
2. The PAL system includes measures to counter phase shift causing
colour issues, so I can only conclude that the system engineers
thought this was a problem with NTSC.

I don't have the time to discuss this at length, but NTSC's unfortunate
reverse-acronym was the result of poor studio standards, and is not inherent
in the system.

It is. Multipath effects caused unacceptable phase and color shifts.

NTSC worked fine on cable, but never as a medium for over air
transmissin with any HINT of multipath.

PAL incorporated phase alternation to partly compensate for
transmission problems (non-linear group delay) in Europe.

sorry, that's a factor of ANY RF tranmission where more than one path to
teh receiver exists.


And fwiw, IIUC PAL rendered colours are designed to alternate the
error line after line rather than get each line colour correct, so
like many such measures it usually solves the problem, but not always.

Correct. That's why color errors roughly cancelled out, at the expense of
loss of satruation.

? huh?

Bit of a Con Really - Follow-up ...
 

"The Natural Philosopher" wrote in message
...
dennis@home wrote:


"The Natural Philosopher" wrote in message
...
Andy Champ wrote:
The Natural Philosopher wrote:

Color transparencies which are used in pro film applications say your
are a liar.

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


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.

No it is not!

A transparency is a subtractive process.
An lcd is additive.

Think again.

I have, you are still wrong.



Each pixel in a film transparency has three filter layers each of which
can absorb a colour.


I've not heard of pixels with respect to film before. Make it up as we go
along?

Each pixel on an lcd is made from three different colour subpixels.
The subpixels each have a colour filter behind them to make them RGorB.

Which amounts to the same thing in practice.

No it does not.

You need different spectra for an additive system and a subtractive system.

Bit of a Con Really - Follow-up ...
 

In article ,
tony sayer wrote:
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.


Is anyone making grade one CRT monitors or hi spec CRT's still?...

I'm told they are - but not the small sizes which also run off batteries
for location use.

--
*One nice thing about egotists: they don't talk about other people.

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

Bit of a Con Really - Follow-up ...
 

In article ,
The Natural Philosopher wrote:
But then different makes of transparencies give different results...

And transparencies are usually used for top quality magazine prints not
'projected onto a screen' anyway.

And are adjusted as part of the printing process.

--
*If love is blind, why is lingerie so popular? *

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

Bit of a Con Really - Follow-up ...
 

In article ,
William Sommerwerck wrote:
I don't have the time to discuss this at length, but NTSC's unfortunate
reverse-acronym was the result of poor studio standards, and is not
inherent in the system. PAL incorporated phase alternation to partly
compensate for transmission problems (non-linear group delay) in Europe.

IIRC, nowt to do with studios, but the transmission process. Hence the
tint control on NTSC sets which is absent on PAL ones.

If I remember my BBC training correctly, NTSC gives theoretically better
'studio' pictures than PAL. Obviously ignoring line and frame frequency.
PAL best for VTR recording, and SECAM the best for transmission.

--
*Pentium wise, pen and paper foolish *

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

Bit of a Con Really - Follow-up ...
 

I don't have the time to discuss this at length, but NTSC's
unfortunate reverse-acronym was the result of poor studio
standards, and is not inherent in the system.

It is. Multipath effects caused unacceptable phase and color shifts.

This is like saying that the design of eggs is fundamentally flawed, because
if you drop them, they break.