LCD Resolution

I understand pixel resolution when applied to computer screens but am
a wee bit puzzled re LCD TV Screens

I was viewing similar sized screens in a department store today and
some branded screens were 640x480 (I'm almost certain I remember that
correctly) whereas others were 1024x768.

Now on a computer screen I know the higher res allows more to be seen
on the screen but the TV is a fixed image so what does the higher res
on a small screen give.

Geoff Lane

"Geoff Lane" wrote in message
...
I understand pixel resolution when applied to computer screens but am
a wee bit puzzled re LCD TV Screens

I was viewing similar sized screens in a department store today and
some branded screens were 640x480 (I'm almost certain I remember that
correctly) whereas others were 1024x768.

Now on a computer screen I know the higher res allows more to be seen
on the screen but the TV is a fixed image so what does the higher res
on a small screen give.

All it means is that they've used the same LCD as they used to make a
computer screen but put it in a TV instead.

UK standard definition TV has 576 lines (it's called 625 lines but only 576
are part of the picture).

It's less easy to say how wide the UK TV picture is in pixels but if we
assume square pixels it comes to 768 pixels wide.

The ideal LCD for a UK standard TV would be 768*576 or maybe 720*576 with
non square pixels.

Smaller LCDs will definitely not be able to show the full transmitted
resolution.

LCDs with somewhat more pixels (such as 1024*768) will also not be so good
due to the process of interpolating up to the higher resolution.

LCDs with many more pixels (such as 1920*1080) will be pretty good too and
are more versatile in that they can display other resolutions well too.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

Geoff Lane wrote:
I understand pixel resolution when applied to computer screens but am
a wee bit puzzled re LCD TV Screens

I was viewing similar sized screens in a department store today and
some branded screens were 640x480 (I'm almost certain I remember that
correctly) whereas others were 1024x768.

Now on a computer screen I know the higher res allows more to be seen
on the screen but the TV is a fixed image so what does the higher res
on a small screen give.

Uk standard broadcast resolution is 768*576.
When this is displayed on an LCD screen with a lower resolution then some of
the lines are effectively discarded resulting in a less than ideal picture.
When this is displayed on an LCD screen with a higher resolution then the tv
has to scale it up by interpolating the 576 lines of information across the
768 , resulting in a less than ideal picture. On the upside it would be more
suitable for use as a PC monitor as well.

The best image quality for standard broadcast material would be on a screen
with exactly the same resolution (or an exact multiple) but as most cheapo
tvs are made using old technology pc monitor panels that's not likely to
happen. A fact that seems to have eluded many of the people who have bought
these sets.

For Hi-Def TVs there are two more resolutions to consider , 768 and 1080
lines and the same basic principle will apply. The picture can be scaled up
or down if the resolution of the screen doesn't match that of the source but
the best results will be when they match.


--
Alex

"I laugh in the face of danger. Then I hide until it goes away"

www.drzoidberg.co.uk www.ebayfaq.co.uk

In message , Dr Zoidberg
wrote

The best image quality for standard broadcast material would be on a screen
with exactly the same resolution (or an exact multiple)

but only if the interconnection is digital and the electronics within
the screen match input to display element pixel for pixel. Any
re-sampling (digital/analogue/digital or digital/digital conversion)
will result in some loss of 'quality'.

--
Alan
news2006 {at} amac {dot} f2s {dot} com

On Sun, 17 Dec 2006 19:51:11 +0000, Geoff Lane
wrote:

I understand pixel resolution when applied to computer screens but am
a wee bit puzzled re LCD TV Screens

I was viewing similar sized screens in a department store today and
some branded screens were 640x480 (I'm almost certain I remember that
correctly) whereas others were 1024x768.

Now on a computer screen I know the higher res allows more to be seen
on the screen but the TV is a fixed image so what does the higher res
on a small screen give.

Geoff Lane

I bought what was supposed to be a 16:9 set (Toshiba 17 inch). When I
got home I noticed the specification was 15:9. I took it back and
before I had said much to the sales assistant the manager came over
and told him to refund the money.

Scott

Scott wrote:
On Sun, 17 Dec 2006 19:51:11 +0000, Geoff Lane
wrote:

I understand pixel resolution when applied to computer screens but am
a wee bit puzzled re LCD TV Screens

I was viewing similar sized screens in a department store today and
some branded screens were 640x480 (I'm almost certain I remember that
correctly) whereas others were 1024x768.

Now on a computer screen I know the higher res allows more to be seen
on the screen but the TV is a fixed image so what does the higher res
on a small screen give.

Geoff Lane

I bought what was supposed to be a 16:9 set (Toshiba 17 inch). When I
got home I noticed the specification was 15:9. I took it back and
before I had said much to the sales assistant the manager came over
and told him to refund the money.

Yep , some LCD sets are either 15:9 or 16:10 panels. Not a problem for PC
use but for TV's it's less than ideal.

--
Alex

"I laugh in the face of danger. Then I hide until it goes away"

www.drzoidberg.co.uk www.ebayfaq.co.uk

Dr Zoidberg wrote:

For Hi-Def TVs there are two more resolutions to consider , 768 and 1080
lines and the same basic principle will apply.

Almost - 720 lines, not 768. Yes, a huge number of "HD Ready" LCD and
Plasma panels are 768 lines. Yes, this does mean that they cannot display
any standard or high definition image without scaling. Yes, this sucks.

NTSC: 640x480 (sometimes considered 720x480; Google for more)
PAL: 720x576 (sometimes considered 704x576 or 768x576; Google for more)
HD 1: 1280x720
HD 2: 1920x1080

There is also a progressive scan version of 640x480 that some people
count as HD. It's certainly higher resolution than 480i provided the
material has been produced with 480p presentation in mind.

Note that standard def PAL is higher resolution, but lower frame rate,
than standard def NTSC. Note also that HD is the same resolution
regardless of territory, but the UK gets a lower frame rate. HD from US
regions broadcast in the UK will often have to go through a frame rate
conversion process, interfering with picture quality.

Since most 1080 broadcasts are interlaced - very few sources do 1080p and
some HD TVs can't display it - panels must do deinterlacing. This
interferes with picture quality.

HD includes an overscan region at about 10% per edge. Some HD sets let
you control whether or not the picture is scaled and cropped before being
placed on the panel, or shown without the cropping. Many do not. This
means you can have a 1920x1080 panel and *still* be watching scaled video
with a 1920x1080 broadcast. This interferes with picture quality.

If you've read this far, you probably get the idea! :-) HD seems to be
about selling you a new TV, a new STB, a new DVD player and a premium
rate content service - it's not really about best picture quality.

--
TTFN, Andrew Hodgkinson
Find some electronic music at: Photos, wallpaper, software and mo
http://pond.org.uk/music.html http://pond.org.uk/

Andrew Hodgkinson wrote:
Dr Zoidberg wrote:

For Hi-Def TVs there are two more resolutions to consider , 768 and
1080 lines and the same basic principle will apply.

Almost - 720 lines, not 768.

D'oh , brain fade.
Of course it's 720 lines.


HD includes an overscan region at about 10% per edge. Some HD sets let
you control whether or not the picture is scaled and cropped before
being placed on the panel, or shown without the cropping. Many do
not. This means you can have a 1920x1080 panel and *still* be
watching scaled video with a 1920x1080 broadcast. This interferes
with picture quality.

The Sony W series I've been playing with lets you choose.
It's obvious when using the PC inputs but on broadcast or other soruces many
people would be unaware,

If you've read this far, you probably get the idea! :-) HD seems to be
about selling you a new TV, a new STB, a new DVD player and a premium
rate content service - it's not really about best picture quality.

Agreed
--
Alex

"I laugh in the face of danger. Then I hide until it goes away"

www.drzoidberg.co.uk www.ebayfaq.co.uk

Andrew Hodgkinson wrote:

[snip good explanation of why you almost never get 1:1 pixel mapping]

If you've read this far, you probably get the idea! :-) HD seems to be
about selling you a new TV, a new STB, a new DVD player and a premium
rate content service - it's not really about best picture quality.

I look at it another way. This is the first generation HD kit (for the
UK at least). It's being sold to people who either desperately want it,
or can afford it.

Both these groups of people will probably go out and buy second
generation HD kit that does the job better, when they discover that
their first generation HD kit is not ideal. They may even go on to buy
third generation kit that does the job properly!

The rest of us wouldn't buy the first generation kit even if it was
perfect. We'll wait for cheaper second generation kit, or good third
generation kit.

Given this, where is the incentive for manufacturers to make first
generation kit that does the job properly?

(Maybe I'm too cynical!).

Let's be very clear, for best (optimal) results...

For watching films, you need a disc, player, and display that can
handle 1080p24 without any conversion (other than frame
doubling/tripling). The discs are "here" (well, in the USA at least)
already, the players are appearing (ditto), maybe the latest displays
do this properly too. However, I doubt you'll find any of these kinds
of discs, players or displays in your local shops, and Joe public
certainly isn't going to find one in their search for HD!

For watching live content, you need a means of displaying 1080i50(25)
for UK HD content, and ideally 720p60, 720p50, and 1080i60(30). Future
proof with 1080p50 and 1080p60, handle high quality domestic drama and
sped-up film with 1080p25 correctly detected when fed as 1080sf, and
you have all HD bases covered.

For watching all non-HD content, you need a means of displaying 576i,
576p, and ideally 480i and 480p.

Multiple HDCP enabled inputs goes without saying.

All these different formats and frame rates need to be displayed
without temporal or spatial conversion artefacts, without exacerbating
the limitations of the lower quality formats, and with appropriate or
no overscan. Further, all formats need to be handled optimally and
seamlessly by the display device without intervention from the user.

If anyone spots a display that can do all of this, please let me know.
I doubt many of the magazines who are so keen to declare this or that
HDTV as being "the best" even understand the tests required to check
all this functionality, never mind have the equipment to carry out the
tests themselves.

Cheers,
David.

wrote in message
ups.com...

....snipsy...


For watching films, you need a disc, player, and display that can
handle 1080p24 without any conversion (other than frame
doubling/tripling). The discs are "here" (well, in the USA at least)
already, the players are appearing (ditto), maybe the latest displays
do this properly too. However, I doubt you'll find any of these kinds
of discs, players or displays in your local shops, and Joe public
certainly isn't going to find one in their search for HD!


Well not strictly true as Comet has the Samsung Bluray player with a 1080p
display currently on sale (£999 & £1800 respectively last time I was there).
Quite stunning results

--
Paul Schofield