The limit to brightness
 

Chatting to a neighbour recently he suggested to me that the modern telly as
he put it, was not good at bright and dark. I think hebasically meant that
bright was kind of dull and blacks were not black enough. I suggested more
contrast, but...
Not now being able to see, I would have thought this criticism of lcds was
now a thing of the past, but are we still in this stage, or has he just not
bought a good enough telly I wonder?

Bit daft I said asking me, I don't even have a screen on mine!

Brian

--
From the Sofa of Brian Gaff Reply address is active

The limit to brightness
 

Brian Gaff wrote:

I think hebasically meant
that bright was kind of dull and blacks were not black enough. I
suggested more contrast, but...

In terms of brightness, I would say my (expensive) Sony LCD TV is at
least the equal of any CRT TV I've owned.

Contrast is another issue, though. Cheap LCD TVs still seem to suffer
from glowing blacks, greatly reducing the apparent contrast ratio.

I spent a fortune to get a TV with zoned backlighting, so the black
bits of the picture really are completely dark.

Having said that, I don't think backlight bleed is much of a problem
these days unless you are unduly fussy (like me).

I think your neighbour has probably bought a cheap 'n' nasty TV (quite
possible); set it up wrongly (also quite possible); or is an extremely
fussy type (less likely).

--
SteveT

The limit to brightness
 

"Steve Thackery" wrote in message
...
Brian Gaff wrote:

I think hebasically meant that bright was kind of dull and blacks were
not black enough. I suggested more contrast, but...

In terms of brightness, I would say my (expensive) Sony LCD TV is at least
the equal of any CRT TV I've owned.

Contrast is another issue, though. Cheap LCD TVs still seem to suffer
from glowing blacks, greatly reducing the apparent contrast ratio.

I spent a fortune to get a TV with zoned backlighting, so the black bits
of the picture really are completely dark.

Having said that, I don't think backlight bleed is much of a problem these
days unless you are unduly fussy (like me).

I think your neighbour has probably bought a cheap 'n' nasty TV (quite
possible); set it up wrongly (also quite possible); or is an extremely
fussy type (less likely).

For me, the big problem with modern TVs (and this includes CRTs) is that
they cannot handle highlights well, and suffer horrendous crushing of
anything over a certain threshold. At best, when all three colours are
maxed-out, you just get featureless white. At worst, one of the colours
maxes-out and the other two still have usable detail, giving repulsive
magenta or cyan colour-casts. Overexposure on faces makes them even more
orange than a certain presenter of antiques programmes!

Comparing my 25-year-old 14" JVC telly against my 10-year-old Panasonic
(even when the latter was brand-new), the difference was fairly noticeable.
My fiancée's Samsung LCD TV is horrible, especially when playing through
HDMI from Blu-Ray discs or the Sky box, despite my surreptitiously tweaking
brightness, contrast and colour when she's not around to see if I can
improve things.

The limit to brightness
 

On Thu, 30 Aug 2012 19:19:14 +0100, Steve Thackery wrote:

Contrast is another issue, though. Cheap LCD TVs still seem to suffer
from glowing blacks, greatly reducing the apparent contrast ratio.

But the manufacturers tell you they've got a million to one contrast
ratio on their screens, so you must be wrong and it's your eyes that
are at fault.

Or they could just be making it up as they go along.

The limit to brightness
 

On 30/08/2012 19:19, Steve Thackery wrote:
I spent a fortune to get a TV with zoned backlighting, so the black bits
of the picture really are completely dark.

Hmm. I discussed this one with a salesman (yes, I know... but his
replay made sense). They've dropped this technology because although the
black bits in the middle of a dark area are great, the black bits next
to a bright bit aren't dark at all. Which means if you have a big black
bit next to a bright bit some of them aren't as black as others.

Wearing my engineer's hat it occurs to me that calibration must be a
nightmare too. As you've got one is this true?

Mind, I suspect my Sony has vignetting in the corners. But I hardly
ever notice, and when I do have trouble convincing myself it isn't a
shot effect or something...

Andy

The limit to brightness
 

Paul Ratcliffe writes:

On Thu, 30 Aug 2012 19:19:14 +0100, Steve Thackery wrote:

Contrast is another issue, though. Cheap LCD TVs still seem to suffer
from glowing blacks, greatly reducing the apparent contrast ratio.

But the manufacturers tell you they've got a million to one contrast
ratio on their screens, so you must be wrong and it's your eyes that
are at fault.

Or they could just be making it up as they go along.

Maybe that is the reason that the TV stations no longer broadcast the
testcard - so that people will not discover that it is impossible to
correctly adjust the set so that the greyscale bars correctly progress
from black to white with a contrast between each section. I wonder how
many people now take the trouble to adjust a new TV set - first with the
saturation right down (ie monochrome display) and iteratively adjust
brightness and contrast to get black black and white white with the
correct greyscale progression, and only what that is correct turn up the
saturation to make the colour bars and the skin tone look correct.

The limit to brightness
 

Mortimer wrote:

For me, the big problem with modern TVs (and this includes CRTs) is that
they cannot handle highlights well, and suffer horrendous crushing of
anything over a certain threshold. At best, when all three colours are
maxed-out, you just get featureless white.

Yep, good point, and there seem to be two potential causes. Firstly,
the screen itself may not have a linear response to brightness, such
that luminance values higher than a certain level tend to "crush".

But I think the more likely scenario is that the picture data itself
too often "tops out" at 256, 256, 256 RGB (so to speak - I don't know
the actual dynamic range of a TV picture).

If the latter is the case the screen itself is probably behaving
correctly and displaying "fully white" when it is told to, and the
problem is earlier in the chain.

I wonder whereabouts in the chain this "topping out" occurs. My
suspicion is at the broadcast end. But it is also possible that the
bit-depth of the video circuitry in the TV, or of the LCD screen
itself, is less than the bit-depth transmitted, in which case you'd get
that same visible problem.

We need someone in the industry to tell us which it is.

Of course, if the problem is at the broadcast end of the chain (as I
suspect) we would see exactly the same effect on a CRT TV. Perhaps the
problem isn't to do with LCD vs. CRTs, but really about analogue vs.
digital transmissions.

The fact that this "crushing" problem seems to occur only occasionally
makes me think it's due to crap cameras or broadcast equipment.

--
SteveT

The limit to brightness
 

Andy Champ wrote:

They've dropped this technology because although the black
bits in the middle of a dark area are great, the black bits next to a
bright bit aren't dark at all.

Correct, in theory. Zoned backlighting can only work "perfectly" when
there's a backlight LED for every pixel. None of the ones you can buy
are even close.

The nett effect is well known and called "blooming". It is only really
noticeable when you've got white writing on a black background.
Because the backlight has a coarser resolution than the display pixels,
you get a slight backlight glow surrounding the white letters.

It's important to emphasise that this is no worse than a normal
backlight bleed. In fact, another way to think of it is that, with a
non-zoned LCD screen, the "blooming" spreads right across the whole
screen.

The salesman's "big black bit next to a bright bit - some of them
aren't as black as others" is a non-problem in real life. I'm pretty
OCD about my TV picture and have studied it in indecent detail; there
are no visible artefacts like the salesman described, only the
white-text-on-a-black-background blooming effect. (I suppose in theory
you might be able to see blooming when looking at a starfield with a
black background, but I've never noticed it.)

So, zoned backlighting is not perfect - there is some blooming under
those particular conditions. But the question is - is it better than a
non-zoned backlight?

And for me, the answer is a definite and emphatic YES. Way, way
better. On my TV I only ever see blooming when looking at the
programme or film credits, whereas I can see normal backlight bleed in
every dark scene, and it drives me mad.

It's particularly annoying when it's streaky or patchy, which I'm
afraid it so often is. Three years ago I blew £1.5k on a Sony, and
there was a backlight streak at all four corners, pointing diagonally
inwards towards the centre of the screen. It drove me so mad I gave
the TV away after less than a year.

Just recently I looked at a very expensive Samsung 8000 series(they
still use edge lighting) in a darkened showroom and the backlight was
clearly visible - but, worst of all, was patchy like looking at clouds
in a night sky.

I did try dynamic backlighting (on that £1.5k Sony) - you know, where
the backlight is dimmed on dark scenes which would normally show
backlight bleed. But it's awful! You can see a dreadful "pumping"
effect whenever the picture make-up changes - it drove me mad.

I replaced the Sony with a similarly-priced Panasonic plasma, but the
refresh flicker (visible to me on all the plasmas I've seen) was just
too annoying to live with. That got sold as well.

In the end it cost me a stunning £3.5k to find a TV that I really
liked: a 55" LCD Sony with zoned backlighting. Not perfect (the
blooming is visible) but it is such a small defect, and in all other
respects it is so good, that I'm happy with it.

--
SteveT

The limit to brightness
 

In article , Steve Thackery
writes
Mortimer wrote:

For me, the big problem with modern TVs (and this includes CRTs) is that
they cannot handle highlights well, and suffer horrendous crushing of
anything over a certain threshold. At best, when all three colours are
maxed-out, you just get featureless white.

Yep, good point, and there seem to be two potential causes. Firstly,
the screen itself may not have a linear response to brightness, such
that luminance values higher than a certain level tend to "crush".

But I think the more likely scenario is that the picture data itself
too often "tops out" at 256, 256, 256 RGB (so to speak - I don't know
the actual dynamic range of a TV picture).

If the latter is the case the screen itself is probably behaving
correctly and displaying "fully white" when it is told to, and the
problem is earlier in the chain.

I wonder whereabouts in the chain this "topping out" occurs. My
suspicion is at the broadcast end. But it is also possible that the
bit-depth of the video circuitry in the TV, or of the LCD screen
itself, is less than the bit-depth transmitted, in which case you'd get
that same visible problem.

If it was at the broadcast end then all TV's, including CRTs, would
suffer from it at the same time, on the same images. They don't, so it
isn't at broadcast.

Its more likely to be related to how some panels handle the gamma
processing inherent in video. Gamma was necessary in the days of CRTs
due to their inherent non-linear response but is still beneficial today
as a means of data compression. If video was linearly encoded then most
of the precision in the highlights would simply be wasted, since you
need much more linear precision to see subtle shadow changes than you
need for highlights. Gamma attempts to even out the quantisation, so
approximately the same precision is used to quantify discernable
differences in shadows as highlights.

Still images use gamma as well. Most digital cameras digitise the video
signal off the sensor to 12-bit precision, some high end SLRs now do 14
or even 16-bit precision. However the jpg images they produce only need
8-bit precision for each primary colour. Jpg images are gamma encoded,
usually with the 2.2 gamma defined by the sRGB colorspace that has
become the defacto standard of the PC world (or the 1.8 gamma of Macs).

LCDs are, by comparison, fairly linear and the video signal, which is
already precompensated with a gamma response close to the inverse of the
phosphors of old CRTs (eg. 2.5 for PAL, 2.2 for NTSC) needs to be gamma
encoded within the set. How that is implemented and to what precision
can result in the "topping out" referred to.
--
Kennedy

The limit to brightness
 

Steve Thackery wrote:


It's particularly annoying when it's streaky or patchy, which I'm afraid
it so often is. Three years ago I blew £1.5k on a Sony, and there was a
backlight streak at all four corners, pointing diagonally inwards
towards the centre of the screen. It drove me so mad I gave the TV away
after less than a year.
Can I be your friend, just in case it ever happens again?

Bill

The limit to brightness
 

R. Kennedy McEwen wrote:

need for highlights. Gamma attempts to even out the quantisation, so
approximately the same precision is used to quantify discernable
differences in shadows as highlights.

Gamma 2.2 significantly over-corrects and results in shadows having
limited perceptual resolution. The gamma used by the Mac is closer to
the human eye's response.

True sRGB actually goes linear for the darkest shadows.

Gamma 2.2 is dictated by the empirical behaviour of CRTs and was
presumably chosen to make TV receiver hardware cheap (and similar for
IBM PC hardware).

The limit to brightness
 

Graham Murray wrote:

from black to white with a contrast between each section. I wonder how
many people now take the trouble to adjust a new TV set - first with the

Probably only slightly fewer than did so for analogue, i.e. not many at all!

The limit to brightness
 

"Steve Thackery" wrote in message
...
Mortimer wrote:

For me, the big problem with modern TVs (and this includes CRTs) is that
they cannot handle highlights well, and suffer horrendous crushing of
anything over a certain threshold. At best, when all three colours are
maxed-out, you just get featureless white.

Yep, good point, and there seem to be two potential causes. Firstly, the
screen itself may not have a linear response to brightness, such that
luminance values higher than a certain level tend to "crush".

But I think the more likely scenario is that the picture data itself too
often "tops out" at 256, 256, 256 RGB (so to speak - I don't know the
actual dynamic range of a TV picture).

If the latter is the case the screen itself is probably behaving correctly
and displaying "fully white" when it is told to, and the problem is
earlier in the chain.

I wonder whereabouts in the chain this "topping out" occurs. My suspicion
is at the broadcast end. But it is also possible that the bit-depth of
the video circuitry in the TV, or of the LCD screen itself, is less than
the bit-depth transmitted, in which case you'd get that same visible
problem.

We need someone in the industry to tell us which it is.

Of course, if the problem is at the broadcast end of the chain (as I
suspect) we would see exactly the same effect on a CRT TV. Perhaps the
problem isn't to do with LCD vs. CRTs, but really about analogue vs.
digital transmissions.

The fact that this "crushing" problem seems to occur only occasionally
makes me think it's due to crap cameras or broadcast equipment.

It's more noticeable on documentaries such as house makeover or
house-hunting where they are probably using low-budget (and physically
smaller) cameras to keep production costs down and make the cameras less
intrusive, but I've also seen it on some dramas with high production values
(properly graded pictures, etc).

The fact that it is more apparent with modern TVs than older ones, for the
same broadcast, makes me think that it's partly due to the electronics and
screen in the TV.

The limit to brightness
 

In article , David Woolley
writes
R. Kennedy McEwen wrote:

need for highlights. Gamma attempts to even out the quantisation, so
approximately the same precision is used to quantify discernable
differences in shadows as highlights.

Gamma 2.2 significantly over-corrects and results in shadows having
limited perceptual resolution. The gamma used by the Mac is closer to
the human eye's response.

The human eye response is only one factor which determines the ideal
gamma, and the 1.8 gamma of the Mac is no better, given the other
factors, than 2.2.

True sRGB actually goes linear for the darkest shadows.

Correct, which is why I said "attempts" and "approximately". However,
the reason for the linear segment is to reduce the quantisation in
linear space to practical limits.

Gamma 2.2 is dictated by the empirical behaviour of CRTs and was
presumably chosen to make TV receiver hardware cheap (and similar for
IBM PC hardware).
Which made the choice of 1.8 for the original CRT based Macs even more
complex, requiring another (undocumented!) layer of LUT to achieve
linear response.

However, as I said, this is merely an approximation and colour
management/calibration adds another layer of correction to the whole
process.
--
Kennedy

The limit to brightness
 

Graham Murray wrote:
Paul writes:

On Thu, 30 Aug 2012 19:19:14 +0100, Steve wrote:

Contrast is another issue, though. Cheap LCD TVs still seem to suffer
from glowing blacks, greatly reducing the apparent contrast ratio.

But the manufacturers tell you they've got a million to one contrast
ratio on their screens, so you must be wrong and it's your eyes that
are at fault.

Or they could just be making it up as they go along.

Maybe that is the reason that the TV stations no longer broadcast the
testcard - so that people will not discover that it is impossible to
correctly adjust the set so that the greyscale bars correctly progress
from black to white with a contrast between each section. I wonder how
many people now take the trouble to adjust a new TV set - first with the
saturation right down (ie monochrome display) and iteratively adjust
brightness and contrast to get black black and white white with the
correct greyscale progression, and only what that is correct turn up the
saturation to make the colour bars and the skin tone look correct.

That is indeed the correct technique - for analogue CRTs :-)

BugBear

The limit to brightness
 

Steve Thackery wrote:

good stuff

Thank you for a detailed and informative post.

BugBear

The limit to brightness
 

Room lighting?
I turn lighting in the room down, my wife turns room lighting up to full.
They dim the lights at cinemas and theatres.
Even at a modern church we go to.
Regards
David

The limit to brightness
 

R. Kennedy McEwen wrote:

Fascinating post - thanks.

If it was at the broadcast end then all TV's, including CRTs, would
suffer from it at the same time, on the same images. They don't, so it
isn't at broadcast.

That's the only bit I might disagree with. I've certainly noticed the
occasional "topping out" effect on various TVs, including older CRTs.
I've never, though, had the chance to study them in a row to see if the
effect occurs (or doesn't) at the same time on all of them. Have you
done that? Can you confirm that you've seen it occur on some but not
all screens showing the same picture at the same time?

And it is often not associated with full brightness - probably the most
noticeable (because of how we work psychologically) is the familiar
bright orange face, where details are lost.

My TV shows faces beautifully most of the time, but sometimes they cut
to some old material or maybe some kind of Skype link and the reporter
has a topped-out orange face. Surely this is from the broadcast end of
the chain.

Mind you, going back to my first paragraph - we need to be careful
because of course by maladjusting the brightness/contrast/colour
controls you can force your picture to top out, or bottom out, even
with good content. So clearly the effect *can* be more of a problem on
some TVs than others, depending on how they are set up.

In summary, though, I have to say that crushing or topping out is not a
consistent problem on my TV (as judged by my eye). If it were, then
clearly I would agree that the TV was causing it. The fact that it
only occurs sometimes strongly suggests that it has more to do with the
picture *source* in those cases.

But I also agree that you can force it to happen at the TV end by
deliberately maladjusting the brightness/contrast/colour controls.
This shows that the cause may be complex.

--
SteveT

The limit to brightness
 

On Thu, 30 Aug 2012 21:27:42 +0100, Graham Murray
wrote:

Maybe that is the reason that the TV stations no longer broadcast the
testcard - so that people will not discover that it is impossible to
correctly adjust the set so that the greyscale bars correctly progress
from black to white with a contrast between each section.

Is that the case? A few years back there was some key sequence to use on BBC
digital text on Freeview to get a test card on the screen.


--

The limit to brightness
 

On 31/08/2012 09:41, The Other Mike wrote:

Is that the case? A few years back there was some key sequence to use on BBC
digital text on Freeview to get a test card on the screen.

The MHEG test card is still available on the DTT platform: go to LCN105
(BBC red button channel) and press yellow as soon as the MHEG welcome
page appears. Then go to any other channel, and back to 105. This time
press green at the welcome page and you should see a 'status page'.
Press green for the test card and a rendering of TCW will appear after a
short delay.

As noted here before though, this test card isn't terribly useful for
setting up displays. I find, with a CRT display, that for pictures to
look right the TC has to to be set with the blacks somewhat crushed.

--
Andy

The limit to brightness
 

In article ,
Mortimer wrote:
It's more noticeable on documentaries such as house makeover or
house-hunting where they are probably using low-budget (and physically
smaller) cameras to keep production costs down and make the cameras less
intrusive,

More likely a camera lent to the subject to film 'out of hours'

but I've also seen it on some dramas with high production values
(properly graded pictures, etc).

You can't simply shoot with natural contrast ratios. The 'system' simply
can't cope with it. You either have to light the foreground to reduce the
contrast, or reduce the brightest parts with filters of some sort - or a
mixture of both. Modern cameras can also 'bend' the gamma to reduce the
level of highlights. But even with all this some crushing will be accepted
under some conditions.

It's the same sort of thing as happens with audio. If you have a drama
with some whispering and shouting, you have to alter both those levels to
something acceptable for domestic viewing. Not only because the average
domestic set couldn't produce that dynamic range.

--
*Black holes are where God divided by zero *

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

The limit to brightness
 

"Andy Wade" wrote in message
...
On 31/08/2012 09:41, The Other Mike wrote:

Is that the case? A few years back there was some key sequence to use on
BBC
digital text on Freeview to get a test card on the screen.

The MHEG test card is still available on the DTT platform: go to LCN105
(BBC red button channel) and press yellow as soon as the MHEG welcome page
appears. Then go to any other channel, and back to 105. This time press
green at the welcome page and you should see a 'status page'. Press green
for the test card and a rendering of TCW will appear after a short delay.

As noted here before though, this test card isn't terribly useful for
setting up displays. I find, with a CRT display, that for pictures to
look right the TC has to to be set with the blacks somewhat crushed.


Thanks.
Colours etc ok for me on mine.
All borders and squares ok but surprised the middle circle is slightly
squashed.
Regards
David

The limit to brightness
 

In article , R. Kennedy McEwen
wrote:

Gamma 2.2 significantly over-corrects and results in shadows having
limited perceptual resolution. The gamma used by the Mac is closer to
the human eye's response.

The human eye response is only one factor which determines the ideal
gamma, and the 1.8 gamma of the Mac is no better, given the other
factors, than 2.2.

The official PAL spec is 2.8, though as most CRTs are nearer 2.2, that's
what most broadcast cameras are lined up to, or they were when I worked
with them. BBC test chart 57 gives a linear staircase display on a
waveform monitor when gamma is 2.2 near black and 2.5 near white. The
Nikon 990 still camera I once tested on this chart also gave equal
brightness steps, indicating that they use the same gamma values as
television. I have no idea why they chose 1.8 for the Mac, unless it was
just to be different.

Rod.
--

The limit to brightness
 

In article , Paul Ratcliffe wrote:
Contrast is another issue, though. Cheap LCD TVs still seem to suffer
from glowing blacks, greatly reducing the apparent contrast ratio.

But the manufacturers tell you they've got a million to one contrast
ratio on their screens, so you must be wrong and it's your eyes that
are at fault.

The contrast you will see on a screen is not only dependent on the
properties of the screen, but the ambient light falling on it. The darkest
tone any screen can reproduce is the colour of the screen itself when it is
switched off, and under most conditions that isn't anywhere near black.

Or they could just be making it up as they go along.

Now there's a possibility.

Rod.
--

The limit to brightness
 

In article en.co.uk,
Roderick Stewart wrote:

I have no idea why they chose 1.8 for the Mac

Because, back in the mid 80s, it was considered to match printed
output better. Now that serious work is done using colour profiles
for each device, it makes more sense to use a gamma that more closely
matches the display hardware, and recent versions of MacOS X use 2.2
by default.

-- Richard

The limit to brightness
 

Roderick Stewart wrote:

The contrast you will see on a screen is not only dependent on the
properties of the screen, but the ambient light falling on it. The darkest
tone any screen can reproduce is the colour of the screen itself when it is
switched off, and under most conditions that isn't anywhere near black.

Quite !!

At least contemporary screens are a lot 'blacker' than they used to be.

http://www.theexpgroup.com/blog/wp-content/uploads/2010/07/ExP_old_TV1.jpg

The limit to brightness
 

Dave Plowman (News) wrote:

You can't simply shoot with natural contrast ratios. The 'system' simply
can't cope with it. You either have to light the foreground to reduce the
contrast, or reduce the brightest parts with filters of some sort

What sort of filter reduces contract?

Bill

The limit to brightness
 

On Fri, 31 Aug 2012 09:41:05 +0100, The Other Mike
wrote:

On Thu, 30 Aug 2012 21:27:42 +0100, Graham Murray
wrote:

Maybe that is the reason that the TV stations no longer broadcast the
testcard - so that people will not discover that it is impossible to
correctly adjust the set so that the greyscale bars correctly progress
from black to white with a contrast between each section.

Is that the case? A few years back there was some key sequence to use on BBC
digital text on Freeview to get a test card on the screen.

There still is. I have Test Card W showing at the moment:

1) Tune to BBCi on 105
2) When BBCi background appears press Yellow, within 30 seconds
3) Tune to another channel
4) Go back to 105
5) When BBCi background appears press Green, within 30 seconds
6) Wait between 30 seconds and a couple of minutes and TCW should
appear.

This is a simpler sequence than it was 4 years ago when we were told how
to do it in this ng by Roderick Stewart


--
Peter Duncanson
(in uk.tech.digital-tv)

The limit to brightness
 

Dave Plowman (News) wrote:

You can't simply shoot with natural contrast ratios. The 'system' simply
can't cope with it. You

That's interesting - I don't know any of this stuff.

So basically, then, it means there is too much dynamic range in a "real
life" scene for the cameras and the rest of the broadcast chain? Hence
using fill lighting to bring up the shadows. Have I understood
correctly?

I'm glad we got this discussion going - I love learning new stuff. :-)

--
SteveT

The limit to brightness
 

Mark Carver wrote:

At least contemporary screens are a lot 'blacker' than they used to be.

Yes, absolutely, and it's well worth remembering. My Sony LCD is very
dark indeed when it's switched off, but I remember some older CRTs had
a very light screen - like an insipid pale brownish colour. No way
could that produce realistic blacks.

--
SteveT

The limit to brightness
 

In article , Steve Thackery
writes
R. Kennedy McEwen wrote:

Fascinating post - thanks.

If it was at the broadcast end then all TV's, including CRTs, would
suffer from it at the same time, on the same images. They don't, so
it isn't at broadcast.

That's the only bit I might disagree with. I've certainly noticed the
occasional "topping out" effect on various TVs, including older CRTs.
I've never, though, had the chance to study them in a row to see if the
effect occurs (or doesn't) at the same time on all of them. Have you
done that? Can you confirm that you've seen it occur on some but not
all screens showing the same picture at the same time?

I have seen it on shop display racks where some sets show the clipping
effects and others don't but never seen it occur on all the sets
simultaneously, even though all are fed from the same source. Now, it
could be that the source wasn't clipping at the times I have been
viewing, and some sets were just badly set up, but I am fairly content
that the vast majority of the problem is down to individual sets rather
than broadcast, or even the STB, sources.
--
Kennedy

The limit to brightness
 

R. Kennedy McEwen wrote:

.......but I am fairly content
that the vast majority of the problem is down to individual sets rather
than broadcast, or even the STB, sources.

OK, thanks.

--
SteveT

The limit to brightness
 

"Steve Thackery" wrote in message
...
R. Kennedy McEwen wrote:

Fascinating post - thanks.

If it was at the broadcast end then all TV's, including CRTs, would
suffer from it at the same time, on the same images. They don't, so it
isn't at broadcast.

That's the only bit I might disagree with. I've certainly noticed the
occasional "topping out" effect on various TVs, including older CRTs.
I've never, though, had the chance to study them in a row to see if the
effect occurs (or doesn't) at the same time on all of them. Have you done
that? Can you confirm that you've seen it occur on some but not all
screens showing the same picture at the same time?

Yes: I've had my ancient JVC 14" CRT and 10-year-old Panasonic CRT both
tuned to analogue from the same aerial using the same transmitter, and seen
(occasionally) orange faces on the Panasonic but not on the JVC. Maybe the
Panasonic is more sensitive to bad material than the JVC. I think it may
have been "made-on-the-cheap" documentary rather than (eg) news or drama
that provoked it, but it was several years ago that I compared side by side
so I forget he exact details.

A lot of material from Sky box, via HDMI, seems to trigger it on my
fiancee's LCD TV and it's more common and/or more noticeable than via the
TV's built-in DVB decoder or the DVB decoder in her DVB disc recorder via
SCART, though I've not had chance to switch back and forth when I see it on
Sky to compare like with like. I wonder if her TV has separate
brightness/contrast/colour settings for each type of input (internal
analogue, internal DVB, SCART, HDMI).

The limit to brightness
 

In article ,
Bill Wright wrote:
You can't simply shoot with natural contrast ratios. The 'system'
simply can't cope with it. You either have to light the foreground to
reduce the contrast, or reduce the brightest parts with filters of
some sort

What sort of filter reduces contract?

A filter across the window of the room you're shooting in. Etc.

--
*Forget the Joneses, I keep us up with the Simpsons.

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

The limit to brightness
 

In article ,
Steve Thackery wrote:
You can't simply shoot with natural contrast ratios. The 'system' simply
can't cope with it. You

That's interesting - I don't know any of this stuff.

So basically, then, it means there is too much dynamic range in a "real
life" scene for the cameras and the rest of the broadcast chain? Hence
using fill lighting to bring up the shadows. Have I understood
correctly?

It obviously depends on the weather conditions - but with full sunlight,
yes.

I'm glad we got this discussion going - I love learning new stuff. :-)

Rather obvious on any footie match etc where the stand is shading one side
of the pitch, especially when the players have some white in their strip.

--
*Never kick a cow pat on a hot day *

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

The limit to brightness
 

On Fri, 31 Aug 2012 11:57:20 +0100, Bill Wright wrote:

You can't simply shoot with natural contrast ratios. The 'system' simply
can't cope with it. You either have to light the foreground to reduce the
contrast, or reduce the brightest parts with filters of some sort

What sort of filter reduces contract?

A fog filter. Thinking framewise, a graduated filter.

The limit to brightness
 

Steve Thackery wrote:
Mark Carver wrote:

At least contemporary screens are a lot 'blacker' than they used to be.

Yes, absolutely, and it's well worth remembering. My Sony LCD is very
dark indeed when it's switched off, but I remember some older CRTs had a
very light screen - like an insipid pale brownish colour. No way could
that produce realistic blacks.

Don't forget though that in those days it was assumed that viewing was
done in greatly subdued light. People were used to drawing the curtains
and turning the light out to look at images on a screen, because of
movies and magic lanterns.

Also, no-one watched telly in the daytime, and interior lighting was
usually pretty dull. A single 100W bulb in a shade was as good as it got.

Bill

The limit to brightness
 

Dave Plowman (News) wrote:
In article ,
Bill Wright wrote:
You can't simply shoot with natural contrast ratios. The 'system'
simply can't cope with it. You either have to light the foreground to
reduce the contrast, or reduce the brightest parts with filters of
some sort

What sort of filter reduces contract?

A filter across the window of the room you're shooting in. Etc.

A shade then.

Bill

The limit to brightness
 

Dave Plowman (News) wrote:
In article ,
Steve Thackery wrote:
You can't simply shoot with natural contrast ratios. The 'system' simply
can't cope with it. You

That's interesting - I don't know any of this stuff.

So basically, then, it means there is too much dynamic range in a "real
life" scene for the cameras and the rest of the broadcast chain? Hence
using fill lighting to bring up the shadows. Have I understood
correctly?

This is the basis of adjusting the exposure of any kind of photography
to favour the gradation in the highlights or the gradation in the
shadows. Since large burnt out areas look terrible most auto exposure
systems take highlights into extra account, even when set for 'averaging'.

Incidentally I was messing around last year with still photography and
found that if I took a contrasty still life scene at several different
exposures using a tripod, it was possible to combine the shots in
PhotoShop and achieve a wider contrast range. This was of course
artificial and unrealistic, but it looked pretty nice.

Photographic paper used to be supplied in several different contrast
grades. Normally you'd print on Grade 3, but film had a wider range than
that paper, so there was always loss of either highlights or shadows
compared to the negative. Grade 2 would fix it, but often the prints
looked a bit flat unless there were significant areas at both ends of
the range.

Bill

The limit to brightness
 

In article ,
Bill Wright wrote:
Dave Plowman (News) wrote:
In article ,
Bill Wright wrote:
You can't simply shoot with natural contrast ratios. The 'system'
simply can't cope with it. You either have to light the foreground to
reduce the contrast, or reduce the brightest parts with filters of
some sort

What sort of filter reduces contract?

A filter across the window of the room you're shooting in. Etc.

A shade then.

Not really. It's common (in drama) to fit a filter to a window which is
invisible to the camera, so you can still shoot the window. It simply
reduces the light coming through it.

--
*What am I? Flypaper for freaks!?

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