Visual "clipping"?

On Sep 3, 9:25 pm, "Richard Crowley" <rcrow...@xp7rt.net> wrote:

> Prolonged bright areas (whether clipped or not) will damage CRT
> monitors.

Can damage occur to a CRT/Plasma/LCD monitor from an area that is
extremely-bright for an extremely short time? Let's say one attempts
to force 2400 lumens of light-intensity out of an area of the monitor
for around 5 seconds. What damage would affect that region of the
screen?

Warning! Crazy scenarios are presented below. None-the-less I still
find them interesting:

Try to force 100,000,000 lumens out of a square-shaped, pinky-finger-
sized area of an LCD monitor. Now what would happen? Would the organic
material present in that area catch fire?

For an acoustic-analogy, let's say one tries to force a 400,000 Hz,
144 dB sine-wave tone out of a Bose loudspeaker. The result: a very
expensive fire. The plastics/paper in the speaker would likely ignite.

Radium wrote:
> On Sep 3, 9:25 pm, "Richard Crowley" <rcrow...@xp7rt.net> wrote:
> 
>> Prolonged bright areas (whether clipped or not) will damage CRT
>> monitors.
> 
> Can damage occur to a CRT/Plasma/LCD monitor from an area that is
> extremely-bright for an extremely short time? Let's say one attempts
> to force 2400 lumens of light-intensity out of an area of the monitor
> for around 5 seconds. What damage would affect that region of the
> screen?

Ummm, probably none, as the output would be limited by the drive systems 
of the display.  The only thing you could "force" into it would be a 
high-voltage video signal, which would fry the input circuitry, but 
probably not a lot else.

To extend the analogy to audio, your speaker would have its own built-in 
amp with limited output power; you can't "force" it to output more power 
into the speaker.

> Warning! Crazy scenarios are presented below. None-the-less I still
> find them interesting:
> 
> Try to force 100,000,000 lumens out of a square-shaped, pinky-finger-
> sized area of an LCD monitor. Now what would happen? Would the organic
> material present in that area catch fire?

And how exactly would one do that, since LCDs don't actually produce 
light on their own?

On Sep 3, 9:07 pm, Radium <gluceg...@gmail.com> wrote:
> On Sep 3, 8:27 pm, isw <i...@witzend.com> wrote:
> > > What is the visual-equivalent of "clipping"? Is there a difference
> > > between analog and digital in terms of visual-clipping? If so, what is
> > > the difference?
> > Clipping causes whites lose all texture -- very similar to overexposed
> > film.
>
> What does this look like on a screen?

If you can find an old analog TV or monitor, just turn up the contrast
control way too high.  All the greys darker than a certain level
become black, all the greys lighter than a certain level become
white.  Information is lost.

On Tue, 04 Sep 2007 04:31:27 GMT, Matt Ion <soundy106@gmail.com> wrote:

>NOT ON A TRANSMITTER.  Yeesh.  Did you actually read that paragraph AT 
>ALL???

Usually he only reads half. Get used to the phenomenon "Radium".

-m-
-- 
Official website "Jonah's Quid" http://www.jonahsquids.co.uk

On Mon, 03 Sep 2007 20:27:43 -0700, isw <isw@witzend.com> wrote:

>Clipping causes whites lose all texture -- very similar to overexposed 
>film.

White clipping makes you loose the texture, and some other interesting
things occur, like the clipped area turning yellowish (solarization).
But it's not only white which can clip, with colour-correction you can
easily clip one of the three colour-channels. And of course you can clip
black as well, loosing shadow detail.

>> Auditory-clipping can damage speakers. Can visual-"clipping" damage
>> monitors?
>
>No. Prolonged blacks can damage television transmitters, however (video 
>is inverted for transmission, so black requires full power from the 
>transmitter).

I would say the transmitters would be resistant to that. Most run below
their designed maximum power anyway.

cheers

-martin-
-- 
Official website "Jonah's Quid" http://www.jonahsquids.co.uk

In article <1188878846.842063.33390@d55g2000hsg.googlegroups.com>,
 Radium <glucegen1@gmail.com> wrote:

> On Sep 3, 8:27 pm, isw <i...@witzend.com> wrote:
> 
> > In article <1188874984.222039.197...@y42g2000hsy.googlegroups.com>,
> 
> >  Radium <gluceg...@gmail.com> wrote:
> 
> > > Hi:
> 
> > > Clipping in an audio signal results when an audio device receives a
> > > signal that is too loud. The audio signal distorts into square-waves
> > > because the "tops" of the signal are flattened. The device cannot
> > > handle power levels over a certain level. When this level is exceeded,
> > > clipping occurs. Clipping is usually harsher in digital devices than
> > > in analog devices. Analog clipping tends to be fuzzy and soft compared
> > > to digital clipping.
> 
> > > What is the visual-equivalent of "clipping"? Is there a difference
> > > between analog and digital in terms of visual-clipping? If so, what is
> > > the difference?
> 
> > Clipping causes whites lose all texture -- very similar to overexposed
> > film.
> 
> What does this look like on a screen?

Just as I said: white areas with no texture.

> > > Auditory-clipping can damage speakers. Can visual-"clipping" damage
> > > monitors?
> 
> > No. Prolonged blacks can damage television transmitters, however (video
> > is inverted for transmission, so black requires full power from the
> > transmitter).
> 
> Prolonged black can damage a monitor/screen? That's weird. White is
> analogous to the loudest sound a loudspeaker can playback. Black is
> analogous to a loudspeaker not being feed any signal.

I did not say "monitor"; I said "transmitter". There *is* a difference.

> When the power-supply of the monitor/screen is turned off, the monitor/
> screen is black because it not receiving any voltage.

It's not voltage; it's current, that determines brightness during the 
normal operation of a monitor.

> I would think that extremely-bright white would damage the screen
> because the brightest white results from the highest voltage applied
> to the Reds, Greens, and Blues [equal intensities of R, G, & B -- if
> combined -- appear white to our eyes when emitted by an electronic
> monitor] in a particular area of the monitor/screen.

Actually it's not voltage; it's current.

And it takes a long time for overdriving to cause damage to an ordinary 
monitor.

> Wouldn't something similar happen to a
> monitor/screen [whether it's a CRT, plasma, or LCD] if it was forced
> to display light-intensities beyond its limits?

CRT's possibly, over a long period of time. LCDs, never. The LCD part is 
just a bunch of "valves"; the light source is usually a fluorescent lamp 
of some sort. No possibility of "burning anything out".

I have been involved with very special CRT-based imaging devices where 
an uncontrolled momentary pulse would destroy the phosphor -- and in 
fact, *drill a pit in the glass of the faceplate*. But that is unlikely 
to ever happen to a CRT used as a video monitor.

Isaac

Radium <glucegen1@gmail.com> wrote:

[..]
> What is the visual-equivalent of "clipping"?

Blowouts.

> Is there a difference between analog and digital in terms of
> visual-clipping?

Yup.

> If so, what is the difference?

Google is your friend.

-- 
http://www.xoverboard.com/cartoons/2007/070416_argument.html

Martin Heffels wrote:
> On Mon, 03 Sep 2007 20:27:43 -0700, isw <isw@witzend.com> wrote:
> 
>> Clipping causes whites lose all texture -- very similar to overexposed 
>> film.
> 
> White clipping makes you loose the texture, and some other interesting
> things occur, like the clipped area turning yellowish (solarization).
> But it's not only white which can clip, with colour-correction you can
> easily clip one of the three colour-channels. And of course you can clip
> black as well, loosing shadow detail.
> 
>>> Auditory-clipping can damage speakers. Can visual-"clipping" damage
>>> monitors?
>> No. Prolonged blacks can damage television transmitters, however (video 
>> is inverted for transmission, so black requires full power from the 
>> transmitter).
> 
> I would say the transmitters would be resistant to that. Most run below
> their designed maximum power anyway.

Guess it's more of a THEORETICAL damage :)

I think the point is, the way they work, it's POSSIBLE, if unlikely.

On Tue, 04 Sep 2007 07:20:55 GMT, Matt Ion <soundy106@gmail.com> wrote:

>I think the point is, the way they work, it's POSSIBLE, if unlikely.

Yes of course :-) They would switch off with all the protections in place.
But it must have happened at one stage, otherwise it wouldn't be known.

-m-
-- 
Official website "Jonah's Quid" http://www.jonahsquids.co.uk

Radium wrote:

(snip)

> What is the visual-equivalent of "clipping"? Is there a difference
> between analog and digital in terms of visual-clipping? If so, what is
> the difference?

Clipping results from the saturation of the system, analog or digital.
That should be true for audio or video.

> Auditory-clipping can damage speakers. Can visual-"clipping" damage
> monitors?

In general, audio clipping does not damage speakers.  The usual
case that causes damage is the combination of a few things:

Using multiple drivers to cover a large frequency range, with
a crossover network to divide up the signal.

Musical audio has much more power at lower frequencies than higher
frequencies, so speakers are designed appropriately.

Clipping generates a lot of power at the higher harmonics of the
input frequencies that goes to drivers not designed for
those power levels.

In most video systems this combination doesn't exist.  It might
in future video reproduction systems, though.

-- glen