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

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.

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

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.

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

wrote:
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.

There's no such thing as a 5000K LCD display, sans backlight. Until you
put light through it, an LCD doesn't have a colour temperature at all.

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.

Yes, it does. It drastically reduces the number of transmission levels
available to the pixels of that colour, causing posterisation & colour
distortion. The more out of whack the colour temperature of the
backlight is in comparison to the desired colour temperature of the
image, the worse the problem will get.
Unlike CRTs, the transmission value of an LCD pixel isn't infinitely
variable, they only work in steps.


--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

wrote in message
...
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


While this is true, it would be virtually impossible to get all colors right
with some arbitrary color backlight. You could get a subset right and get
all the others completely wrong.

Leonard

Leonard Caillouet wrote:
wrote in message
...
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


While this is true, it would be virtually impossible to get all colors right
with some arbitrary color backlight. You could get a subset right and get
all the others completely wrong.

Leonard

With each colour channel you've got everything available from
backlight output x LCD max down to backlight output x LCD minimum.
AFAIK that covers every flesh tone on this planet, unless one goes
down to 2000K backlight or some other very extreme value.


NT

wrote in message
...
Leonard Caillouet wrote:
wrote in message
...
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


While this is true, it would be virtually impossible to get all colors
right
with some arbitrary color backlight. You could get a subset right and
get
all the others completely wrong.

Leonard

With each colour channel you've got everything available from
backlight output x LCD max down to backlight output x LCD minimum.
AFAIK that covers every flesh tone on this planet, unless one goes
down to 2000K backlight or some other very extreme value.


NT


This is simply not true. Every display has a color gamut that is limited by
the maximum saturation of its primaries. You can produce any color within
that gamut but not any outside. Even if every flesh tone is in that gamut,
that does not mean that you will get the right flesh tones for a given
combination of RGB. In order to do so, you must have the same spectrum in
the primaries that you have in the camera filters, the correct colorimetry
for the white point, and the correct application of the decoding matrix. If
you depart from any of these, you can adjust a display for ONE color to be
correct, but everything else will be off.

Leonard

This is simply not true. Every display has a color gamut that is
limited by the maximum saturation of its primaries. You can
produce any color within that gamut but not any outside.

Correct.


Even if every flesh tone is in that gamut, that does not mean that
you will get the right flesh tones for a given combination of RGB.
In order to do so, you must have the same spectrum in the
primaries that you have in the camera filters...

This bothers me. It might be true in a practical sense, but it's always
struck me as being theoretically wrong (mostly because of the extreme
overlap of the eye's blue and green receptors). I won't start an argument,
though, because, even if my intuition is correct, I don't have the "science"
to back it up.

"William Sommerwerck" wrote in message
...
This is simply not true. Every display has a color gamut that is
limited by the maximum saturation of its primaries. You can
produce any color within that gamut but not any outside.

Correct.


Even if every flesh tone is in that gamut, that does not mean that
you will get the right flesh tones for a given combination of RGB.
In order to do so, you must have the same spectrum in the
primaries that you have in the camera filters...

This bothers me. It might be true in a practical sense, but it's always
struck me as being theoretically wrong (mostly because of the extreme
overlap of the eye's blue and green receptors). I won't start an argument,
though, because, even if my intuition is correct, I don't have the
"science"
to back it up.




The overlap is caused by the shape of the standard observer curves and is
part of the very reason that using a narrow band RGB device may not produce
color properly. The CIE standard observer curves are precisely attempts at
modeling the response of the human visual system. For decades, cameras have
been calibrated to match them, and phosphors designed to do the same, to the
degree possible. Now, with narrow spectrum devices, we have to consider the
implications of those assumptions. It may be that in the future, we should
simplify the system and use a narrow band response in cameras and reproduce
the RGB in the same manner at the display. Then we can more easily predict
the output of RGB systems using a standard matrix.

Leonard

wrote:
Leonard Caillouet wrote:
wrote in message
...
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

While this is true, it would be virtually impossible to get all colors right
with some arbitrary color backlight. You could get a subset right and get
all the others completely wrong.

Leonard

With each colour channel you've got everything available from
backlight output x LCD max down to backlight output x LCD minimum.
AFAIK that covers every flesh tone on this planet, unless one goes
down to 2000K backlight or some other very extreme value.

The problem with LCD monitors is they typically only have 6 bits (64
levels) of resolution for each colour channel, so you don't have a lot
of scope for tweaking the WB via the LUTs. Do it that way, & you'll lose
tonal detail, resulting in posterisation.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------