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How many types of screens are there?



 
 
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  #21  
Old October 28th 17, 09:16 PM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
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Posts: 534
Default How many types of screens are there?

On Saturday, 28 October 2017 10:41:50 UTC+1, Brian Gaff wrote:
I was just wondering a person I know was asking me if I knew as almost every
telly in the shops right now claims their screen is the best. Some use leds,
some use lcds some use different methods of back lights some claim extra
pixels of another colour to make pictures look more real and all sorts of
other combinations. I suggested that get the one that looks the best for
your budget. Check things like viewing angle, blacks and perhaps blurring
on moving images etc.
I did wonder though whether any of the various systems has a longer life
than others or has hidden problems, we all recall the Plasma burn on and
loss of brightness over time but of course my only care is that it does not
act like a radio jammer!

Brian


SNIP

Cathode Ray Tube TV's are no longer sold and probably no longer made.

Plasma screens, may be sold, but few are high resolution and they do burn in, losing approx 50% brightness in ten years.

Most current TV's are LCD displays with edge or back illumination.

Early sets had cold cathode tubes along the edges.
Then there were LED's along the edges.
Now there are LED's behind the panel.

All of these work fairly well, although the LED's might have an MBTF of 50,000 hours (six year's constant use).

More recent sets have High Dynamic Range (HDR with sub variants) giving more colours and 4K resolution. Both cost a bit extra and are probably worth paying for.

A few sets are Organic LED. I have my doubts about this technologies durability, but keep the screen out of the sun and is should be OK. My OLED phone display is just fine after 5 years.
  #22  
Old October 28th 17, 09:58 PM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,901
Default How many types of screens are there?

You mean you still have the same phone after five years, blimey.
I have a screenless phone now nearly 8 years old but on its last legs.
Predictably its the case not the phone that is the problem.
Of course when 2g goes off from 2020 to 2025 to make more room for more
modern systems it will become an antique. Spanish made phones are probably
quite rare.
Brian

--
----- -
This newsgroup posting comes to you directly from...
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"R. Mark Clayton" wrote in message
...
On Saturday, 28 October 2017 10:41:50 UTC+1, Brian Gaff wrote:
I was just wondering a person I know was asking me if I knew as almost
every
telly in the shops right now claims their screen is the best. Some use
leds,
some use lcds some use different methods of back lights some claim extra
pixels of another colour to make pictures look more real and all sorts
of
other combinations. I suggested that get the one that looks the best for
your budget. Check things like viewing angle, blacks and perhaps
blurring
on moving images etc.
I did wonder though whether any of the various systems has a longer life
than others or has hidden problems, we all recall the Plasma burn on and
loss of brightness over time but of course my only care is that it does
not
act like a radio jammer!

Brian


SNIP

Cathode Ray Tube TV's are no longer sold and probably no longer made.

Plasma screens, may be sold, but few are high resolution and they do burn
in, losing approx 50% brightness in ten years.

Most current TV's are LCD displays with edge or back illumination.

Early sets had cold cathode tubes along the edges.
Then there were LED's along the edges.
Now there are LED's behind the panel.

All of these work fairly well, although the LED's might have an MBTF of
50,000 hours (six year's constant use).

More recent sets have High Dynamic Range (HDR with sub variants) giving
more colours and 4K resolution. Both cost a bit extra and are probably
worth paying for.

A few sets are Organic LED. I have my doubts about this technologies
durability, but keep the screen out of the sun and is should be OK. My
OLED phone display is just fine after 5 years.



  #23  
Old October 28th 17, 10:54 PM posted to uk.tech.digital-tv
Johnny B Good[_2_]
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Posts: 439
Default How many types of screens are there?

On Sat, 28 Oct 2017 18:32:48 +0100, Max Demian wrote:

On 28/10/2017 17:51, Brian Gaff wrote:
So in other words its a flat strip light which ionises at the
breakdown voltage of the gas with a phosphor on the side that has the
screen.


Actually cold cathode backlights consist of thin cylindrical strip
lights, perhaps one each side, or one at the bottom, or some other
arrangement depending on the size of the screen, with a complex diffuser
which ensures an even backlight.

For a truly flat backlight an electroluminescent display could be used,
which I believe is a solid state device. I don't know how often they are
used, but I recall seeing one demonstrated in the Science Museum in the
early 70s. It had a Philips logo on it.


Electroluminescent panels were the technology of choice for most of
those "Fasten Seatbelts" signs on commercial airliners. Their electrical
characteristic is that of a lossy capacitor. Their brightness is
proportional to both applied voltage and frequency of the supply.

The 400Hz ac supply used on-board large aircraft and airliners alike
allowed the panels to outperform those that were earthbound to a 50 or 60
Hertz supply. These days, of course, that's no longer a problem since a
simple converter can supply such panels with any number of KHz of ac
current rather than a mere 400Hz.

I think nearly all modern LCD TV sets are backlit using LED lamp
technology these days. CCFTs are rather old hat in this application and
obsoleting them in favour of LED backlighting gets rid of the need to
have a KV or so of high frequency voltage floating around the innards of
a TV set.

--
Johnny B Good
  #24  
Old October 28th 17, 11:51 PM posted to uk.tech.digital-tv
Johnny B Good[_2_]
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Posts: 439
Default How many types of screens are there?

On Sat, 28 Oct 2017 18:40:43 +0100, Andy Burns wrote:

Max Demian wrote:

For a truly flat backlight an electroluminescent display could be used


EL materials tend to have a pretty short "half life" i.e. they go dim
after a few years.


When I was reading up on them about 30 or 40 years ago, the problem was
keeping them sealed against moisture ingress as I recall. Checking my
1972 copy of "Lamps and Lighting", I see that it was the organic on
plastic types which needed protection against moisture ingress and tended
to have short lifetimes. The ceramic on glass panels fared much better,
lasting several thousand hours.

The book didn't quote any specific figures in its very short section on
electroluminescent panels which also included the image retaining and the
image storage panel technological spin offs.

At the time, their luminous efficacy was some two to three orders of
magnitude less than a fluorescent lamp. Also, the manufacturers were
still trying to find a an electroluminescent red phosphor to create a
white light version using a phosphor mix alone (as per the fluorescent
lamp's mix of phosphors used to coat the inside walls of the tube.

The pragmatic solution to creating a white light EL panel was to use a
suitable fluorescent paint over the exterior of the glass in the same way
that white LEDs today rely on a blue LED to create the missing red and
green parts of the spectrum by optical excitation of the yellow phosphor
coating.

The book's authors dismissed EL panel technology as a GLS solution. Mind
you they did likewise with LED lamps, also considering them as ideal only
for panel lamps and alphanumeric displays and it's only in hindsight that
we now see just how wrong they were. However, they seem to have got their
assessment of EL panel technology right.

--
Johnny B Good
  #25  
Old October 29th 17, 10:35 AM posted to uk.tech.digital-tv
TonyGamble
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Posts: 77
Default How many types of screens are there?

I am quickly going to correct my earlier post where I challenged the suggestion that plasma reduces its brightness to 50% after ten years.

I said I was on my third plasma. I have looked up my records and this is my second. Mea culpa and How Time Flies.

I bought a Fujitsu 42PWD3 in 1999. That was the one that someone on one of this chat groups said would be best used in its vga mode (in those days everyone relied on composite). An rgb to vga converter was 'invented' by someone at Tadworth. I got the prototype to test and they were put into production by John Sim who had a small av business in Scotland.

In those days we only had SD and no HDTV. The pictures on SD got worse as bandwidth got squeezed by the obsession with multi channels (+1 and all that rubbish). In desperation I moved from vga to component as the Fujitsu offered some sharpening in that mode (none on vga as that was supposed to be used in offices for graphics).

I have no records of what the screen cost but I think it was in the region of £6.5k.

It lasted me to 2011 by which time Richer Sounds were selling Panasonic plasmas for precisely one tenth the price. Also we had moved on from scart to HDMI. I'd been using a series of Tivos (they did not last for ever) but by 2011 we had Sky Plus and Humax to choose from. That was when I moved from Tivo to Humax and bought my present Panasonic 42".

It six years into its ten year cycle and the suggested 50% drop in brightness. When I bought it I used one of those US calibrating DVDs and I can assure you it is on precisely the same settings - and each of them have plenty of slack if I did want to increase the contrast and brightness (do any of you remember how surprised we were to find that you used brightness to correct the shadows and contrast to fine tune the highlights? One thing the DVD taught me.).

I'd love to borrow an OLED and compare it with our Panny - but that sort of service is hard to find in 2017.

So now I await the wisdom of you folk.

Tony


  #26  
Old October 29th 17, 11:06 AM posted to uk.tech.digital-tv
Max Demian
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Posts: 3,836
Default How many types of screens are there?

On 28/10/2017 23:51, Johnny B Good wrote:
On Sat, 28 Oct 2017 18:40:43 +0100, Andy Burns wrote:
Max Demian wrote:


For a truly flat backlight an electroluminescent display could be used


EL materials tend to have a pretty short "half life" i.e. they go dim
after a few years.


When I was reading up on them about 30 or 40 years ago, the problem was
keeping them sealed against moisture ingress as I recall. Checking my
1972 copy of "Lamps and Lighting", I see that it was the organic on
plastic types which needed protection against moisture ingress and tended
to have short lifetimes. The ceramic on glass panels fared much better,
lasting several thousand hours.

[...]

The book's authors dismissed EL panel technology as a GLS solution. Mind
you they did likewise with LED lamps, also considering them as ideal only
for panel lamps and alphanumeric displays and it's only in hindsight that
we now see just how wrong they were. However, they seem to have got their
assessment of EL panel technology right.


I used to have a school textbook published in 1965 which discussed
liquid crystals and concluded they were of no practical use.

I remember it was a limp back book with a purple cover.

--
Max Demian
  #27  
Old October 29th 17, 11:09 AM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
external usenet poster
 
Posts: 534
Default How many types of screens are there?

On Saturday, 28 October 2017 21:58:06 UTC+1, Brian Gaff wrote:
You mean you still have the same phone after five years, blimey.
I have a screenless phone now nearly 8 years old but on its last legs.
Predictably its the case not the phone that is the problem.
Of course when 2g goes off from 2020 to 2025 to make more room for more
modern systems it will become an antique. Spanish made phones are probably
quite rare.
Brian


I have [had] quite a few phones: -

Technophone Mk1/II - analogue, bought March 1986, used to 1992 worked till ~1999. Loaned to MOSI 2005 -2015.
Motorola Elite - analogue, bought from friend ~1992, used to ~1999, suffered sweat damage and later part exchanged.
BT Opal - loaned by BTC after Elite cloned - returned.
Motorola P7389 (locked), bought from BTC ~1999, socket damaged, but still works, O2 P&G SIM
Motorola P7389 (unlocked), supplied by BTC ~2000 afer row over above being locked; Orange P&G SIM
Motorola Ti250, given by BTC ~2001, has Voda inherited P&G SIM. Kept in car.
  #28  
Old October 29th 17, 11:14 AM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Posts: 414
Default How many types of screens are there?

TonyGamble wrote:

I bought a Fujitsu 42PWD3 in 1999.


I went to COMDEX in 1997, 42" plasma screens were just being released
and it seemed every stand had them on demo, they were very impressive
compared to CRTs/LCDs of the time, but extremely pricey.
  #29  
Old October 29th 17, 11:16 AM posted to uk.tech.digital-tv
Indy Jess John
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Posts: 1,226
Default How many types of screens are there?

On 29/10/2017 11:06, Max Demian wrote:

I used to have a school textbook published in 1965 which discussed
liquid crystals and concluded they were of no practical use.


Old books are wonderful like that!
I bought an ancient encyclopaedia from a flea market some years ago.
Under "Aeronautics" it helpfully informs me that "There is no indication
that heavier-than-air flight will ever be commercially viable". :-)

Jim

  #30  
Old October 29th 17, 12:30 PM posted to uk.tech.digital-tv
TonyGamble
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Posts: 77
Default How many types of screens are there?


I went to COMDEX in 1997, 42" plasma screens were just being released
and it seemed every stand had them on demo, they were very impressive
compared to CRTs/LCDs of the time, but extremely pricey.


Snap - but it was the 1998 Photokina where I saw my first batch and decided "I want one of those". Mine came from an office equipment company as they were not televisions. Without a receiver/decoder, and I probably had Sky in those days, they were dumb.

Tony


 




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